EPILEPSIA, Issue 12 2005
Laura Uva
Summary:,Purpose: Aim of the study is to investigate the involvement of parahippocampal subregions in the generation and in the propagation of focal epileptiform discharges in an acute model of seizure generation in the temporal lobe induced by arterial application of bicuculline in the in vitro isolated guinea pig brain preparation. Methods: Electrophysiological recordings were simultaneously performed with single electrodes and multichannel silicon probes in the entorhinal, perirhinal, and piriform cortices and in the area CA1 of the hippocampus of the in vitro isolated guinea pig brain. Interictal and ictal epileptiform discharges restricted to the temporal region were induced by a brief (3,5 min) arterial perfusion of the GABAA receptor antagonist, bicuculline methiodide (50 ,M). Current source density analysis of laminar field profiles performed with the silicon probes was carried out at different sites to establish network interactions responsible for the generation of epileptiform potentials. Nonlinear regression analysis was conducted on extracellular recordings during ictal onset in order to quantify the degree of interaction between fast activities generated at different sites, as well as time delays. Results: Experiments were performed in 31 isolated guinea pig brains. Bicuculline-induced interictal and ictal epileptiform activities that showed variability of spatial propagation and time course in the olfactory,temporal region. The most commonly observed pattern (n = 23) was characterized by the initial appearance of interictal spikes (ISs) in the piriform cortex (PC), which propagated to the lateral entorhinal region. Independent and asynchronous preictal spikes originated in the entorhinal cortex (EC)/hippocampus and progressed into ictal fast discharges (around 25 Hz) restricted to the entorhinal/hippocampal region. The local generation of fast activity was verified and confirmed both by CSD and phase shift analysis performed on laminar profiles. Fast activity was followed by synchronous afterdischarges that propagated to the perirhinal cortex (PRC) (but not to the PC). Within 1,9 min, the ictal discharge ceased and a postictal period of depression occurred, after which periodic ISs in the PC resumed. Unlike preictal ISs, postictal ISs propagated to the PRC. Conclusions: Several studies proposed that reciprocal connections between the entorhinal and the PRC are under a very efficient inhibitory control (1). We report that ISs determined by acute bicuculline treatment in the isolated guinea pig brain progress from the PC to the hippocampus/EC just before ictal onset. Ictal discharges are characterized by a peculiar pattern of fast activity that originates from the entorhinal/hippocampal region and only secondarily propagates to the PRC. Postictal propagation of ISs to the PRC occured exclusively when an ictal discharge was generated in the hippocampal/entorhinal region. The results suggest that reiteration of ictal events may promote changes in propagation pattern of epileptiform discharges that could act as trigger elements in the development of temporal lobe epilepsy. [source]

Increased Expression of the Neuronal Glutamate Transporter (EAAT3/EAAC1) in Hippocampal and Neocortical Epilepsy

EPILEPSIA, Issue 3 2002
Peter B. Crino
Summary: ,Purpose: To define the changes in gene and protein expression of the neuronal glutamate transporter (EAAT3/EAAC1) in a rat model of temporal lobe epilepsy as well as in human hippocampal and neocortical epilepsy. Methods: The expression of EAAT3/EAAC1 mRNA was measured by reverse Northern blotting in single dissociated hippocampal dentate granule cells from rats with pilocarpine-induced temporal lobe epilepsy (TLE) and age-matched controls, in dentate granule cells from hippocampal surgical specimens from patients with TLE, and in dysplastic neurons microdissected from human focal cortical dysplasia specimens. Immunolabeling of rat and human hippocampi and cortical dysplasia tissue with EAAT3/EAAC1 antibodies served to corroborate the mRNA expression analysis. Results: The expression of EAAT3/EAAC1 mRNA was increased by nearly threefold in dentate granule cells from rats with spontaneous seizures compared with dentate granule cells from control rats. EAAT3/EAAC1 mRNA levels also were high in human dentate granule cells from patients with TLE and were significantly elevated in dysplastic neurons in cortical dysplasia compared with nondysplastic neurons from postmortem control tissue. No difference in expression of another glutamate transporter, EAAT2/GLT-1, was observed. Immunolabeling demonstrated that EAAT3/EAAC1 protein expression was enhanced in dentate granule cells from both rats and humans with TLE as well as in dysplastic neurons from human cortical dysplasia tissue. Conclusions: Elevations of EAAT3/EAAC1 mRNA and protein levels are present in neurons from hippocampus and neocortex in both rats and humans with epilepsy. Upregulation of EAAT3/EAAC1 in hippocampal and neocortical epilepsy may be an important modulator of extracellular glutamate concentrations and may occur as a response to recurrent seizures in these cell types. [source]

Binding partners L1 cell adhesion molecule and the ezrin-radixin-moesin (ERM) proteins are involved in development and the regenerative response to injury of hippocampal and cortical neurons

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2004
Matilda A. Haas
Abstract Regeneration of the adult central nervous system may require recapitulation of developmental events and therefore involve the re-expression of developmentally significant proteins. We have investigated whether the L1 cell adhesion molecule, and its binding partner, the ezrin-radixin-moesin (ERM) proteins are involved in the neuronal regenerative response to injury. Hippocampal and cortical neurons were cultured in vitro on either an L1 substrate or poly-L-lysine, and ERM and other neuronal proteins were localized immunocytochemically both developmentally and following neurite transection of neurons maintained in long-term culture. Activated ERM was localized to growth cones up to 7 days in vitro but relatively mature cultures (21 days in vitro) were devoid of active ERM proteins. However, ERM proteins were localized to the growth cones of sprouting neuronal processes that formed several hours after neurite transection. In addition, the L1 substrate, relative to poly-L-lysine, resulted in significantly longer regenerative neurites, as well as larger growth cones with more filopodia. Furthermore, neurons derived from the cortex formed significantly longer post-injury neurite sprouts at 6 h post-injury than hippocampal derived neurons grown on both substrates. We have demonstrated that L1 and the ERM proteins are involved in the neuronal response to injury, and that neurons derived from the hippocampus and cortex may have different post-injury regenerative neurite sprouting abilities. [source]

Time-dependent involvement of the dorsal hippocampus in trace fear conditioning in mice

HIPPOCAMPUS, Issue 4 2005
Ilga Misane
Abstract Hippocampal and amygdaloid neuroplasticity are important substrates for Pavlovian fear conditioning. The hippocampus has been implicated in trace fear conditioning. However, a systematic investigation of the significance of the trace interval has not yet been performed. Therefore, this study analyzed the time-dependent involvement of N-methyl- D -aspartate (NMDA) receptors in the dorsal hippocampus in one-trial auditory trace fear conditioning in C57BL/6J mice. The NMDA receptor antagonist APV was injected bilaterally into the dorsal hippocampus 15 min before training. Mice were exposed to tone (conditioned stimulus [CS]) and footshock (unconditioned stimulus [US]) in the conditioning context without delay (0 s) or with CS-US (trace) intervals of 1,45 s. Conditioned auditory fear was determined 24 h after training by the assessment of freezing and computerized evaluation of inactivity in a new context; 2 h later, context-dependent memory was tested in the conditioning context. NMDA receptor blockade by APV markedly impaired conditioned auditory fear at trace intervals of 15 s and 30 s, but not at shorter trace intervals. A 45-s trace interval prevented the formation of conditioned tone-dependent fear. Context-dependent memory was always impaired by APV treatment independent of the trace interval. The results indicate that the dorsal hippocampus and its NMDA receptors play an important role in auditory trace fear conditioning at trace intervals of 15,30-s length. In contrast, NMDA receptors in the dorsal hippocampus are unequivocally involved in contextual fear conditioning independent of the trace interval. The results point at a time-dependent role of the dorsal hippocampus in encoding of noncontingent explicit stimuli. Preprocessing of long CS-US contingencies in the hippocampus appears to be important for the final information processing and execution of fear memories through amygdala circuits. © 2005 Wiley-Liss, Inc. [source]

Selected Line Difference in the Effects of Ethanol Dependence and Withdrawal on Allopregnanolone Levels and 5,-Reductase Enzyme Activity and Expression

ALCOHOLISM, Issue 12 2009
Michelle A. Tanchuck
Background:, Allopregnanolone (ALLO) is a progesterone derivative that rapidly potentiates ,-aminobutyric acidA (GABAA) receptor-mediated inhibition and modulates symptoms of ethanol withdrawal. Because clinical and preclinical data indicate that ALLO levels are inversely related to symptoms of withdrawal, the present studies determined whether ethanol dependence and withdrawal differentially altered plasma and cortical ALLO levels in mice selectively bred for differences in ethanol withdrawal severity and determined whether the alterations in ALLO levels corresponded to a concomitant change in activity and expression of the biosynthetic enzyme 5,-reductase. Methods:, Male Withdrawal Seizure-Prone (WSP) and -Resistant (WSR) mice were exposed to 72 hours ethanol vapor or air and euthanized at select times following removal from the inhalation chambers. Blood was collected for analysis of ALLO and corticosterone levels by radioimmunoassay. Dissected amygdala, hippocampus, midbrain, and cortex as well as adrenals were examined for 5,-reductase enzyme activity and expression levels. Results:, Plasma ALLO was decreased significantly only in WSP mice, and this corresponded to a decrease in adrenal 5,-reductase expression. Cortical ALLO was decreased up to 54% in WSP mice and up to 46% in WSR mice, with a similar decrease in cortical 5,-reductase activity during withdrawal in the lines. While cortical gene expression was significantly decreased during withdrawal in WSP mice, there was a 4-fold increase in expression in the WSR line during withdrawal. Hippocampal 5,-reductase activity and gene expression was decreased only in dependent WSP mice. Conclusions:, These results suggest that there are line and brain regional differences in the regulation of the neurosteroid biosynthetic enzyme 5,-reductase during ethanol dependence and withdrawal. In conjunction with the finding that WSP mice exhibit reduced sensitivity to ALLO during withdrawal, the present results are consistent with the hypothesis that genetic differences in ethanol withdrawal severity are due, in part, to modulatory effects of GABAergic neurosteroids such as ALLO. [source]

Hippocampal interictal spikes disrupt cognition in rats

ANNALS OF NEUROLOGY, Issue 2 2010
Jonathan K. Kleen BS
Objective Cognitive impairment is common in epilepsy, particularly in memory function. Interictal spikes (IISs) are thought to disrupt cognition, but it is difficult to delineate their contribution from general impairments in memory produced by etiology and seizures. We investigated the transient impact of focal IISs on the hippocampus, a structure crucial for learning and memory and yet highly prone to IISs in temporal lobe epilepsy (TLE). Methods Bilateral hippocampal depth electrodes were implanted into 14 Sprague-Dawley rats, followed by intrahippocampal pilocarpine or saline infusion unilaterally. Rats that developed chronic spikes were trained in a hippocampal-dependent operant behavior task, delayed-match-to-sample. Depth-electroencephalogram (EEG) was recorded during 5,562 trials among five rats, and within-subject analyses evaluated the impact of hippocampal spikes on short-term memory operations. Results Hippocampal spikes that occurred during memory retrieval strongly impaired performance (p < 0.001). However, spikes that occurred during memory encoding or memory maintenance did not affect performance in those trials. Hippocampal spikes also affected response latency, adding approximately 0.48 seconds to the time taken to respond (p < 0.001). Interpretation We found that focal IIS-related interference in cognition extends to structures in the limbic system, which required intrahippocampal recordings. Hippocampal spikes seem most harmful if they occur when hippocampal function is critical, extending human studies showing that cortical spikes are most disruptive during active cortical functioning. The cumulative effects of spikes could therefore impact general cognitive functioning. These results strengthen the argument that suppression of IISs may improve memory and cognitive performance in patients with epilepsy. ANN NEUROL 2010;67:250,257 [source]

Amygdala reduction in patients with ADHD compared with major depression and healthy volunteers

ACTA PSYCHIATRICA SCANDINAVICA, Issue 2 2010
T. Frodl
Frodl T, Stauber J, Schaaff N, Koutsouleris N, Scheuerecker J, Ewers M, Omerovic M, Opgen-Rhein M, Hampel H, Reiser M, Möller H.-J, Meisenzahl E. Amygdala reduction in patients with ADHD compared with major depression and healthy volunteers. Objective:, Results in adult attention deficit hyperactivity disorder (ADHD) on structural brain changes and the clinical relevance are contradictory. The aim of this study was to investigate whether in adult patients with ADHD hippocampal or amygdala volumes differs from that in healthy controls and patients with major depression (MD). Method:, Twenty patients with ADHD, 20 matched patients with MD and 20 healthy controls were studied with high resolution magnetic resonance imaging. Results:, Amygdala volumes in patients with ADHD were bilaterally smaller than in patients with MD and healthy controls. In ADHD, more hyperactivity and less inattention were associated with smaller right amygdala volumes, and more symptoms of depression with larger amygdala volumes. Conclusion:, This study supports findings that the amygdala plays an important role in the systemic brain pathophysiology of ADHD. Whether patients with ADHD and larger amygdala volumes are more vulnerable to affective disorders needs further investigation. [source]

Splice-isoform specific immunolocalization of neuronal nitric oxide synthase in mouse and rat brain reveals that the PDZ-complex-building nNOS, ,-finger is largely exposed to antibodies

DEVELOPMENTAL NEUROBIOLOGY, Issue 4 2007
Kristina Langnaese
Abstract Knock out mice deficient for the splice-isoform ,, of neuronal nitric oxide synthase (nNOS,,) display residual nitric oxide synthase activity and immunosignal. To attribute this signal to the two minor neuronal nitric oxide synthase splice variants, ,, and ,,, we generated isoform-specific anti-peptide antibodies against the nNOS,, specific ,,-finger motif involved in PDZ domain scaffolding and the nNOS,, specific N-terminus. The nNOS,, ,,-finger-specific antibody clearly recognized the 160-kDa band of recombinant nNOS,, on Western blots. Using immunocytochemistry, this antibody displayed, in rats and wild-type mice, a labeling pattern similar to but not identical with that obtained using a commercial pan-nNOS antibody. This similarity indicates that the majority of immunocytochemically detectable nNOS is not likely to be complexed with PDZ-domain proteins via the ,,-finger motif. This conclusion was confirmed by the inhibition of PSD-95/nNOS interaction by the nNOS,, ,,-finger antibody in pull-down assays. By contrast, nNOS,, ,,-finger labeling was clearly reduced in hippocampal and cortical neuropil areas enriched in NMDA receptor complex containing spine synapses. In nNOS,, knock out mice, nNOS,, was not detectable, whereas the pan-nNOS antibody showed a distinct labeling of cell bodies throughout the brain, most likely reflecting ,,/,,-isoforms in these cells. The nNOS,, antibody clearly detected bacterial expressed nNOS,, fusion protein and nNOS,, in overexpressing HEK cells by Western blotting. Immunocytochemically, individual cell bodies in striatum, cerebral cortex, and in some brain stem nuclei were labeled in knock out but not in wild-type mice, indicating an upregulation of nNOS,, in nNOS,, deficient animals. © 2007 Wiley Periodicals, Inc. Develop Neurobiol, 2007 [source]

The heterogeneous distribution of functional synaptic connections in rat hippocampal dissociated neuron cultures

ELECTRONICS & COMMUNICATIONS IN JAPAN, Issue 6 2009
Suguru N. Kudoh
Abstract The dynamics of functional synaptic connections are critical for information processing systems in the brain, such as perception and learning. Using rat hippocampal cells cultured on multielectrode arrays, we investigated the spatiotemporal pattern of spontaneous action potentials. The neurons developed connections and a characteristic high-frequency bursting (HFB) activity was observed transiently. After the period of HFB activity, the distribution of spontaneous activity changed drastically with the appearance of neurons with frequent electrical activity and neurons with little activity in the network. The functional connections of all the combinations of recorded spike trains were estimated and depicted simultaneously in a Connection Map. This map revealed that each culture contained hublike neurons with many functional connections, suggesting that the cultures of dissociated rat hippocampal neurons on multielectrode arrays formed heterogeneous networks of functional connections. In addition, the functional connections were drastically reorganized after the induction of synaptic potentiation, and novel hub neurons emerged. These results indicate that spontaneous activity is enough to construct dynamic assemblies of neurons connected to each other by functional synaptic connections, and that synaptic potentiation can induce reorganization of such assemblies of neurons. © 2009 Wiley Periodicals, Inc. Electron Comm Jpn, 92(6): 41,49, 2009; Published online in Wiley InterScience (www.interscience.wiley.com). DOI 10.1002/ecj.10063 [source]

Anticonvulsant profile and teratogenicity of 3,3-dimethylbutanoylurea: A potential for a second generation drug to valproic acid

EPILEPSIA, Issue 7 2008
Jakob Avi Shimshoni
Summary Purpose: The purpose of this study was to evaluate the anticonvulsant activity and teratogenic potential of branched aliphatic acylureas represented by isovaleroylurea (IVU), pivaloylurea (PVU) and 3,3-dimethylbutanoylurea (DBU), as potential second-generation drugs to valproic acid (VPA). Methods: The anticonvulsant activity of IVU, PVU, and DBU was determined in mice and rats utilizing the maximal electroshock seizure (MES) and the pentylenetetrazole (scMet) tests. The ability of DBU to block electrical-, or chemical-induced seizures was further examined in three acute seizure models: the psychomotor 6 Hz model, the bicuculline and picrotoxin models and one model of chronic epilepsy (i.e., the hippocampal kindled rat model). The induction of neural tube defects (NTDs) by IVU, PVU, and DBU was evaluated after i.p. administration at day 8.5 of gestation to a mouse strain highly susceptible to VPA-induced teratogenicity. The pharmacokinetics of DBU was studied following i.v. administration to rats. Results: DBU emerged as the most potent compound having an MES-ED50of 186 mg/kg (mice) and 64 mg/kg (rats) and an scMet-ED50of 66 mg/kg (mice) and 26 mg/kg (rats). DBU underwent further evaluation in the hippocampal kindled rat (ED50= 35 mg/kg), the psychomotor 6 Hz mouse model (ED50= 80 mg/kg at 32 mA and ED50= 133 mg/kg at 44 mA), the bicuculline- and picrotoxin-induced seizure mouse model (ED50= 205 mg/kg and 167 mg/kg, respectively). In contrast to VPA, DBU, IVU, and PVU did not induce a significant increase in NTDs as compared to control. DBU was eliminated by metabolism with a half-life of 4.5 h. Conclusions: DBU's broad spectrum and potent anticonvulsant activity, along with its high safety margin and favorable pharmacokinetic profile, make it an attractive candidate to become a new, potent, and safe AED. [source]

Decreased Dopamine D2/D3-Receptor Binding in Temporal Lobe Epilepsy: An [18F]Fallypride PET Study

EPILEPSIA, Issue 8 2006
Konrad J. Werhahn
Summary:,Purpose: Although animal data are suggestive, evidence for an alteration of the extrastriatal dopaminergic system in human focal epilepsy is missing. Methods: To quantify D2/D3-receptor density, we studied seven patients with temporal lobe epilepsy (TLE) and nine age-matched controls with positron emission tomography (PET) by using the high-affinity dopamine D2/D3-receptor ligand [18F]Fallypride ([18F]FP) suitable for imaging extrastriatal binding. TLE was defined by interictal and ictal video-EEG, magnetic resonance imaging (MRI), and [18F]fluorodeoxyglucose ([18F]FDG)-PET and was due to hippocampal sclerosis (HS), based on histology in all patients. Primary analysis was based on regions of interest (ROIs) defined on individual MRIs. For each patient, binding potential (BP) was calculated by using the simplified reference tissue model, and the epileptogenic was compared with the unaffected hemisphere in each ROI. To confirm the results, an additional voxel-based group analysis was performed by using statistical parametric mapping. Results: Compared with controls, [18F]FP BP was significantly decreased in the epileptogenic temporal lobe in all patients. On ROI analysis, this reduction was evident in areas surrounding the seizure-onset zone at the pole (,34.2%) and lateral aspects (,32.9%) of the temporal lobe. Although the hippocampus [18F]FDG uptake (,8.1%) and hippocampal MR volume (,35.1%) were significantly reduced, no significant decrease of [18F]FP BP was found. Reduction of [18F]FP BP did not correlate with hippocampal atrophy. Conclusions: D2/D3-receptor binding is reduced at the pole and in lateral aspects of the epileptogenic temporal lobe in patients with mesial TLE and HS. This area might correspond to "the irritative zone," indicating that D2/D3 receptors might play a specific role in the pathophysiology of mesial TLE. [source]

Cerebral Damage in Epilepsy: A Population-based Longitudinal Quantitative MRI Study

EPILEPSIA, Issue 9 2005
Rebecca S. N. Liu
Summary:,Purpose: Whether cerebral damage results from epileptic seizures remains a contentious issue. We report on the first longitudinal community-based quantitative magnetic resonance imaging (MRI) study to investigate the effect of seizures on the hippocampus, cerebellum, and neocortex. Methods: One hundred seventy-nine patients with epilepsy (66 temporal lobe epilepsy, 51 extratemporal partial epilepsy, and 62 generalized epilepsy) and 90 control subjects underwent two MRI brain scans 3.5 years apart. Automated and manual measurement techniques identified changes in global and regional brain volumes and hippocampal T2 relaxation times. Results: Baseline hippocampal volumes were significantly reduced in patients with temporal lobe epilepsy and could be attributed to an antecedent neurologic insult. Rates of hippocampal, cerebral, and cerebellar atrophy were not syndrome specific and were similar in control and patient groups. Global and regional brain atrophy was determined primarily by age. A prior neurologic insult was associated with reduced hippocampal and cerebellar volumes and an increased rate of cerebellar atrophy. Significant atrophy of the hippocampus, neocortex, or cerebellum occurred in 17% of patients compared with 6.7% of control subjects. Patients with and without significant volume reduction were comparable in terms of seizure frequency, antiepileptic drug (AED) use, and epilepsy duration, with no identifiable risk factors for the development of atrophy. Conclusions: Overt structural cerebral damage is not an inevitable consequence of epileptic seizures. In general, brain volume reduction in epilepsy is the cumulative effect of an initial precipitating injury and age-related cerebral atrophy. Significant atrophy developed in individual patients, particularly those with temporal lobe and generalized epilepsy. Longer periods of observation may detect more subtle effects of seizures. [source]

Brain Blood-flow Alterations Induced by Therapeutic Vagus Nerve Stimulation in Partial Epilepsy: II.

EPILEPSIA, Issue 9 2004
Low Levels of Stimulation, Prolonged Effects at High
Summary:,Purpose: To measure vagus nerve stimulation (VNS)-induced cerebral blood flow (CBF) effects after prolonged VNS and to compare these effects with immediate VNS effects on CBF. Methods: Ten consenting partial epilepsy patients had positron emission tomography (PET) with intravenous [15O]H2O. Each had three control scans without VNS and three scans during 30 s of VNS, within 20 h after VNS began (immediate-effect study), and repeated after 3 months of VNS (prolonged study). After intrasubject subtraction of control from stimulation scans, images were anatomically transformed for intersubject averaging and superimposed on magnetic resonance imaging (MRI) for anatomic localization. Changes on t-statistical maps were considered significant at p < 0.05 (corrected for multiple comparisons). Results: During prolonged studies, CBF changes were not observed in any regions that did not have CBF changes during immediate-effect studies. During both types of studies, VNS-induced CBF increases were similarly located in the bilateral thalami, hypothalami, inferior cerebellar hemispheres, and right postcentral gyrus. During immediate-effect studies, VNS decreased bilateral hippocampal, amygdalar, and cingulate CBF and increased bilateral insular CBF; no significant CBF changes were observed in these regions during prolonged studies. Mean seizure frequency decreased by 25% over a 3-month period between immediate and prolonged PET studies, compared with 3 months before VNS began. Conclusions: Seizure control improved during a period over which some immediate VNS-induced CBF changes declined (mainly over cortical regions), whereas other VNS-induced CBF changes persisted (mainly over subcortical regions). Altered synaptic activities at sites of persisting VNS-induced CBF changes may reflect antiseizure actions. [source]

A Kindling Model of Pharmacoresistant Temporal Lobe Epilepsy in Sprague,Dawley Rats Induced by Coriaria Lactone and Its Possible Mechanism

EPILEPSIA, Issue 4 2003
Ying Wang
Summary: ,Purpose: The aim of this study was to develop a new animal model of pharmacoresistant temporal lobe epilepsy (TLE) by repeated intramuscular injection of Coriaria lactone (CL) at subthreshold dosages and to explore the mechanisms that might be involved. Methods: Healthy male Sprague,Dawley rats (n = 160) were randomized into four groups during the kindling process: three groups (n = 50 for each group) received CL injection at subthreshold dosages (1.25, 1.5, and 1.75 mg/kg, respectively), and ten received normal saline (NS) injection as a control group. The maximal human adult dosage of carbamazepine (CBZ), valproate (VPA), and phenytoin (PHT) was administered as monotherapy to different groups of kindled rats for 1 month (n = 20 for each group). Changes in EEG recording, seizure number, intensity (expressed as grade 1,5 according to Racine stage), and duration, including spontaneous seizures during different interventions, were compared. The expression of P-170, a multiple drug resistance gene (MDR1) encoding P-glycoprotein, was measured in brain samples from different groups of experimental rats by using an image analysis and measurement system (ImagePro-Plus 4.0). Results: A total of 70 (46.7%) rats were fully kindled with a median of 15 (seven to 20) CL injections. Electrocorticogram (ECoG) including hippocampal (EHG) monitoring revealed the temporal lobe origins of epileptiform potentials, which were consistent with the behavioral changes observed. Spontaneous seizures occurred with frequency and diurnal patterns similar to those of human TLE. The antiepileptic drugs (AEDs) tested lacked a satisfactory seizure control. The maximal P-170 expression was in the kindled rats with AED treatment; the next highest was in the kindled rats without AED intervention. Nonkindled SD rats with CL injection also had increased P-170 expression compared with control SD rats. Conclusions: The study provided a simple and stable animal TLE kindling model with pharmacoresistant properties. The pharmacoresistance observed in the kindled rats to CBZ, VPA, and PHT at maximal human adult dosages together with the increased P-170 expression was a distinct feature of this model. This model might be used in further investigations of the mechanisms involved in pharmacoresistant TLE and for developing new AEDs. [source]

Increased Expression of the Neuronal Glutamate Transporter (EAAT3/EAAC1) in Hippocampal and Neocortical Epilepsy

Anticonvulsant Profile and Teratogenicity of N -methyl-tetramethylcyclopropyl Carboxamide: A New Antiepileptic Drug

EPILEPSIA, Issue 2 2002
Nina Isoherranen
Summary: ,Purpose: The studies presented here represent our efforts to investigate the anticonvulsant activity of N -methyl-tetramethylcyclopropyl carboxamide (M-TMCD) and its metabolite tetramethylcyclopropyl carboxamide (TMCD) in various animal (rodent) models of human epilepsy, and to evaluate their ability to induce neural tube defects (NTDs) and neurotoxicity. Methods: The anticonvulsant activity of M-TMCD and TMCD was determined after intraperitoneal (i.p.) administration to CF#1 mice, and either oral or i.p. administration to Sprague,Dawley rats. The ability of M-TMCD and TMCD to block electrical-, chemical-, or sensory-induced seizures was examined in eight animal models of epilepsy. The plasma and brain concentrations of M-TMCD and TMCD were determined in the CF#1 mice after i.p. administration. The induction of NTDs by M-TMCD and TMCD was evaluated after a single i.p. administration at day 8.5 of gestation in a highly inbred mouse strain (SWV) that is susceptible to valproic acid,induced neural tube defects. Results: In mice, M-TMCD afforded protection against maximal electroshock (MES)-induced, pentylenetetrazol (Metrazol)-induced, and bicuculline-induced seizures, as well as against 6-Hz "psychomotor" seizures and sound-induced seizures with ED50 values of 99, 39, 81, 51, and 10 mg/kg, respectively. In rats, M-TMCD effectively prevented MES- and Metrazol-induced seizures and secondarily generalized seizures in hippocampal kindled rats (ED50 values of 82, 45, and 39 mg/kg, respectively). Unlike M-TMCD, TMCD was active only against Metrazol-induced seizures in mice and rats (ED50 values of 57 and 52 mg/kg, respectively). Neither M-TMCD nor TMCD was found to induce NTDs in SWV mice. Conclusions: The results obtained in this study show that M-TMCD is a broad-spectrum anticonvulsant drug that does not induce NTDs and support additional studies to evaluate its full therapeutic potential. [source]

Electroencephalographic Characterization of an Adult Rat Model of Radiation-Induced Cortical Dysplasia

EPILEPSIA, Issue 10 2001
Shinji Kondo
Summary: ,Purpose: Cortical dysplasia (CD) is a frequent cause of medically intractable focal epilepsy. The mechanisms of CD-induced epileptogenicity remain unknown. The difficulty in obtaining and testing human tissue warrants the identification and characterization of animal model(s) of CD that share most of the clinical, electroencephalographic (EEG), and histopathologic characteristics of human CD. In this study, we report on the in vivo EEG characterization of the radiation-induced model of CD. Methods: Timed-pregnant Sprague,Dawley rats were irradiated on E17 using a single dose of 145 cGy or left untreated. Their litters were identified and implanted with bifrontal epidural and hippocampal depth electrodes for prolonged continuous EEG recordings. After prolonged EEG monitoring, animals were killed and their brains sectioned and stained for histologic studies. Results: In utero,irradiated rats showed frequent spontaneous interictal epileptiform spikes and spontaneous seizures arising independently from the hippocampal or the frontal neocortical structures. No epileptiform or seizure activities were recorded from age-matched control rats. Histologic studies showed the presence of multiple cortical areas of neuronal clustering and disorganization. Moreover, pyramidal cell dispersion was seen in the CA1>CA3 areas of the hippocampal formations. Conclusions: Our results further characterize the in vivo EEG characteristics of the in utero radiation model of CD using long-term EEG monitoring. This model may be used to study the molecular and cellular changes in epileptogenic CD and to test the efficacy of newer antiepileptic medications. [source]

The Midline Thalamus: Alterations and a Potential Role in Limbic Epilepsy

EPILEPSIA, Issue 8 2001
Edward H. Bertram
Summary: ,Purpose: In limbic or mesial temporal lobe epilepsy, much attention has been given to specific regions or cell populations (e.g., the hippocampus or dentate granule cells). Epileptic seizures may involve broader changes in neural circuits, and evidence suggests that subcortical regions may play a role. In this study we examined the midline thalamic regions for involvement in limbic seizures, changes in anatomy and physiology, and the potential role for this region in limbic seizures and epilepsy Methods: Using two rat models for limbic epilepsy (hippocampal kindled and chronic spontaneous limbic epilepsy) we examined the midline thalamus for evidence of involvement in seizure activity, alterations in structure, changes in the basic in vitro physiology of the thalamic neurons. We also explored how this region may influence limbic seizures. Results: The midline thalamus was consistently involved with seizure activity from the onset, and there was significant neuronal loss in the medial dorsal and reuniens/rhomboid nuclei. In addition, thalamic neurons had changes in synaptically mediated and voltage-gated responses. Infusion of lidocaine into the midline thalamus significantly shortened afterdischarge duration. Conclusions: These observations suggest that this thalamic region is part of the neural circuitry of limbic epilepsy and may play a significant role in seizure modulation. Local neuronal changes can enhance the excitability of the thalamolimbic circuits. [source]

Comparison of Intrinsic Optical Signals Associated with Low Mg2+, and 4-Aminopyridine,Induced Seizure-Like Events Reveals Characteristic Features in Adult Rat Limbic System

EPILEPSIA, Issue 6 2000
Katharina Buchheim
Summary: Purpose: To analyze the intrinsic optical signal change associated with seizure-like events in two frequently used in vitro models,the low-Mg2+ and the 4-aminopyridine (4-AP) models,and to monitor regions of onset and spread patterns of these discharges by using imaging of intrinsic optical signals (IOS). Methods: Combined hippocampal,entorhinal,cortex slices of adult rats were exposed to two different treatments: lowering extracellular Mg2+ concentrations or application of 100 ,M 4-AP. The electrographic features of the discharges were monitored using extracellular microelectrodes. Optical imaging was achieved by infrared transillumination of the slice and analysis of changes in light transmission using a subtraction approach. The electrographic features were compared with the optical changes. Regions of onset and spread patterns were analyzed in relevant anatomic regions of the slice. Results: Both lowering extracellular Mg2+ concentrations and application of 4-AP induced seizure-like events. The relative duration of the intrinsic optical signal change associated with seizure-like events in the low-Mg2+ model was significantly longer compared with that seen with those occurring in the 4-AP model, although duration of field potentials did not differ significantly in the two models. Seizure-like events of the low-Mg2+ model originated predominantly in the entorhinal cortex, with subsequent propagation toward the subiculum and neocortical structures. In contrast, no consistent region of onset or spread patterns were seen in the 4-AP model, indicating that the seizure initiation is not confined to a particular region in this model. Conclusions: We conclude that different forms of spontaneous epileptiform activity are associated with characteristic optical signal changes and that optical imaging represents an excellent method to assess regions of seizure onset and spread patterns. [source]

Blockade of caspase-1 increases neurogenesis in the aged hippocampus

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2007
Carmelina Gemma
Abstract Adult hippocampal neurogenesis dramatically decreases with increasing age, and it has been proposed that this decline contributes to age-related memory deficits. Central inflammation contributes significantly to the decrease in neurogenesis associated with ageing. Interleukin-1, is a proinflammatory cytokine initially synthesized as an inactive precursor that is cleaved by caspase-1 to generate the biologically active mature form. Whether IL-1, affects neurogenesis in the aged hippocampus is unknown. Here we analysed cells positive for 5-bromo-2-deoxyuridine (BrdU; 50 mg/kg) in animals in which cleavage of IL-1, was inhibited by the caspase-1 inhibitor Ac-YVAD-CMK (10 pmol). Aged (22 months) and young (4 months) rats received Ac-YVAD-CMK for 28 days intracerebroventricularly through a brain infusion cannula connected to an osmotic minipump. Starting on day 14, animals received a daily injection of BrdU for five consecutive days. Unbiased stereology analyses performed 10 days after the last injection of BrdU revealed that the total number of newborn cells generated over a 5-day period was higher in young rats than in aged rats. In addition, there was a 53% increase in the number of BrdU-labelled cells of the aged Ac-YVAD-CMK-treated rats compared to aged controls. Immunofluorescence studies were performed to identify the cellular phenotype of BrdU-labelled cells. The increase in BrdU-positive cells was not due to a change in the proportion of cells expressing neuronal or glial phenotypes in the subgranular zone. These findings demonstrate that the intracerebroventricular administration of Ac-YVAD-CMK reversed the decrease in hippocampal neurogenesis associated with ageing. [source]

Individual differences in the effects of chronic prazosin hydrochloride treatment on hippocampal mineralocorticoid and glucocorticoid receptors

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2007
Mohamed Kabbaj
Abstract The aim of this study was to investigate the noradrenergic regulation of mineralocorticoid receptors (MRs) and glucocorticoid receptors (GRs) in high responder (HR) and low responder (LR) male rats, an animal model of individual differences in hypothalamo-pituitary-adrenal axis activity and vulnerability to drugs of abuse. The effects of a chronic treatment with the noradrenergic ,1 antagonist (1-[4-amino-6,7-dimethoxy-2-quinazolinyl]-4-[2-furanylcarbonyl] piperazine) hydrochloride (prazosin) (0.5 mg/kg, i.p., 35 days) were assessed on stress-induced corticosterone (CORT) secretion and on hippocampal MRs and GRs in adrenally intact rats. In order to ascertain whether the effects of chronic prazosin treatment on hippocampal MRs and GRs were direct or indirect, through prazosin-induced CORT secretion, we also assessed the effects of the same treatment on adrenalectomized rats with CORT substitutive therapy. When compared with LR rats, HR rats exhibited a delayed return to the basal level of CORT following acute restraint stress; this was associated with a lower binding of MRs and GRs in HR rats than in LR rats. Chronic prazosin treatment had no effect in HR animals but markedly reduced hippocampal MRs and GRs, and increased stress-induced CORT secretion in LR rats. In LR adrenalectomized rats, prazosin reduced hipppocampal MRs but did not change GRs. Our results provide evidence of a differential regulation by noradrenaline of hippocampal MRs and GRs in HR and LR rats. These data could have clinical implications in terms of individual differences in the resistance to antidepressant treatments and individual differences in drug abuse. [source]

Astrocytes promote neurogenesis from oligodendrocyte precursor cells

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 4 2006
P. M. Gaughwin
Abstract The oligodendrocyte precursor cell (OPC) has until recently been regarded as a lineage-restricted precursor cell. Considerable interest has been generated by reports suggesting that OPCs may possess a wider differentiation potential than previously assumed and thus be considered a multipotential stem cell. This study examined the neuronal differentiation potential of rat, postnatal cortical OPCs in response to extracellular cues in vitro and in vivo. OPCs did not exhibit intrinsic neuronal potential and were restricted to oligodendrocyte lineage potential following treatment with the neural precursor mitogen fibroblast growth factor 2. In contrast, a postnatal hippocampal astrocyte-derived signal(s) is sufficient to induce functional neuronal differentiation of cortical OPCs in vitro in population and single cell studies. Co-treatment with Noggin, a bone morphogenetic protein antagonist, did not attenuate neuronal differentiation. Following transplantation to the adult rat hippocampus, cortical OPCs expressed doublecortin, a neuroblast-associated marker. The present findings show that hippocampal, astrocyte-derived signals can induce the neuronal differentiation of OPCs through a Noggin-independent mechanism. [source]

Projections from the hippocampal region to the mammillary bodies in macaque monkeys

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2005
John P. Aggleton
Abstract A combination of anterograde and retrograde tracers mapped the direct hippocampal and parahippocampal inputs to the mammillary bodies in two species of macaque monkey. Dense projections arose from pyramidal cells in layer III of the subiculum and prosubiculum, and terminated in the medial mammillary nucleus. While there was no evidence of an input from the dentate gyrus or fields CA1,3, a small contribution arose from the presubiculum and entorhinal cortices. All of the hippocampal and parahippocampal projections to the mammillary bodies appeared to use the fornix as a route. The caudal portions of the subiculum and prosubiculum contained the greatest numbers of cells projecting to the mammillary bodies. A light contralateral projection to the medial mammillary nucleus was also observed, although this appeared to arise primarily from the more rostral portions of the subiculum and prosubiculum. There was a crude topography within the medial mammillary nucleus, with the caudal subicular projections terminating in the mid and dorsal portions of the nucleus while the rostral subicular and entorhinal projections terminated in the ventral and lateral portions of the medial nucleus. Light ipsilateral projections throughout the lateral mammillary nucleus were sometimes observed. Comparisons with related studies of the macaque brain showed that the dense hippocampal projections to the mammillary bodies arise from a population of subicular cells separate from those that project to the anterior thalamic nuclei, even though the major output from the mammillary bodies is to the anterior thalamic nuclei. Other comparisons revealed underlying similarities with the corresponding projections in the rat brain. [source]

Enhancement of learning behaviour by a potent nitric oxide-guanylate cyclase activator YC-1

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 6 2005
Wei-Lin Chien
Abstract Memory is one of the most fundamental mental processes, and various approaches have been used to understand the mechanisms underlying this process. Nitric oxide (NO), cGMP and protein kinase G (PKG) are involved in the modulation of synaptic plasticity in various brain regions. YC-1, which is a benzylindazole derivative, greatly potentiated the response of soluble guanylate cyclase to NO (up to several hundreds fold). We have previously shown that YC-1 markedly enhances long-term potentiation in hippocampal and amygdala slices via NO-cGMP-PKG-dependent pathway. We here further investigated whether YC-1 promotes learning behaviour in Morris water maze and avoidance tests. It was found that YC-1 shortened the escape latency in the task of water maze, increased and decreased the retention scores in passive and active avoidance task, respectively. Administration of YC-1 30 min after foot-shock stimulation did not significantly affect retention scores in response to passive avoidance test. Administration of scopolamine, a muscarinic antagonist, markedly impaired the memory acquisition. Pretreatment of YC-1 inhibited the scopolamine-induced learning deficit. The enhancement of learning behaviour by YC-1 was antagonized by intracerebroventricular injection of NOS inhibitor L-NAME and PKG inhibitors of KT5823 and Rp-8-Br-PET-cGMPS, indicating that NO-cGMP-PKG pathway is also involved in the learning enhancement action of YC-1. YC-1 is thus a good drug candidate for the improvement of learning and memory. [source]

Binding partners L1 cell adhesion molecule and the ezrin-radixin-moesin (ERM) proteins are involved in development and the regenerative response to injury of hippocampal and cortical neurons

Electrophysiological characterization of interlaminar entorhinal connections: an essential link for re-entrance in the hippocampal,entorhinal system

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 11 2003
Fabian Kloosterman
Abstract The hippocampal formation communicates with the neocortex mainly through the adjacent entorhinal cortex. Neurons projecting to the hippocampal formation are found in the superficial layers of the entorhinal cortex and are largely segregated from the neurons receiving hippocampal output, which are located in deep entorhinal layers. We studied the communication between deep and superficial entorhinal layers in the anaesthetized rat using field potential recordings, current source density analysis and single unit measurements. We found that subiculum stimulation was able to excite entorhinal neurons in deep layers. This response was followed by current sinks in superficial layers. Both responses were subject to frequency dependent facilitation, but not depression. Selective blockade of deep layer responses also abolished subsequent superficial layer responses. This clearly demonstrates a functional deep-to-superficial layer communication in the entorhinal cortex, which can be triggered by hippocampal output. This pathway may provide a means by which processed hippocampal output is integrated or compared with new incoming information in superficial entorhinal layers, and it constitutes an important link in the process of re-entrance of activity in the hippocampal,entorhinal network, which may be important for consolidation of memories or retaining information for short periods. [source]

Rat strain differences in peripheral and central serotonin transporter protein expression and function

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 3 2003
Francesca Fernandez
Abstract Female Fischer 344 (F344) rats have been shown to display increased serotonin transporter (5-HTT) gene expression in the dorsal raphe, compared to female Lewis (LEW) rats. Herein, we explored, by means of synaptosomal preparations and in vivo microdialysis, whether central, but also peripheral, 5-HTT protein expression/function differ between strains. Midbrain and hippocampal [3H]paroxetine binding at the 5-HTT and hippocampal [3H]serotonin (5-HT) reuptake were increased in male and female F344 rats, compared to their LEW counterparts, these strain differences being observed both in rats of commercial origin and in homebred rats. Moreover, in homebred rats, it was found that these strain differences extended to blood platelet 5-HTT protein expression and function. Saturation studies of midbrain and hippocampal [3H]paroxetine binding at the 5-HTT, and hippocampal and blood platelet [3H]5-HT reuptake, also revealed significant strain differences in Bmax and Vmax values. Although F344 and LEW rats differ in the activity of the hypothalamo-pituitary-adrenal (HPA) axis, manipulations of that axis revealed that the strain differences in hippocampal [3H]paroxetine binding at 5-HTTs and [3H]5-HT reuptake were not accounted for by corticosteroids. Hippocampal extracellular 5-HT levels were reduced in F344 rats, compared to LEW rats, with the relative, but not the absolute, increase in extracellular 5-HT elicited by the local administration of citalopram being larger in F344 rats. Because the aforementioned strain differences did not lie in the coding sequences of the 5-HTT gene, our results open the promising hypothesis that F344 and LEW strains model functional polymorphisms in the promoter region of the human 5-HTT gene. [source]

Human brain carboxypeptidase B, which cleaves ,-amyloid peptides in vitro, is expressed in the endoplasmic reticulum of neurons

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 9 2001
Akira Matsumoto
Abstract Intracellular localization of novel human brain carboxypeptidase B (HBCPB) was investigated in human hippocampus, using immunohistochemistry by confocal laser microscopy and biochemical purification of the homogenate by density gradient ultracentrifugation. The former revealed that the majority of HBCPB was expressed in the endoplasmic reticulum, in which the HBCPB-specific C14-module immunoreactivity was colocalized with GRP78 immunoreactivity, a stress 70 heat shock protein specifically expressed in the endoplasmic reticulum. The latter showed that anti-C14-module immunoreactivity and prepro-HBCPB immunoreactivity were both enriched in the microsome fraction, especially in that of the endoplasmic reticulum-density fraction of normal human hippocampal homogenates from various sources. However, HBCPB prepared from human hippocampus showed exopeptidase activity for synthetic ,-amyloid 1,42 peptide, in which A, X-42 C-terminus immunoreactivity was decreased in a fashion dose-dependent of the amount of the protease added. These findings indicate that HBCPB, which is expressed in the endoplasmic reticulum of a group of neuronal perikarya, may play an important physiological role in degradation of ,-amyloid 1,42, which is specifically generated in the endoplasmic reticulum of human and rodent neurons and is also regarded as the most pathogenic and aggregatable species among all ,-amyloid peptides. [source]

Overexpression of spermidine/spermine N1 -acetyltransferase in transgenic mice protects the animals from kainate-induced toxicity

EUROPEAN JOURNAL OF NEUROSCIENCE, Issue 2 2000
Kyllikki Kaasinen
Abstract We recently generated a transgenic mouse line with activated polyamine catabolism through overexpression of spermidine/spermine N1 -acetyltransferase (SSAT). A detailed analysis of brain polyamine concentrations indicated that all brain regions of these animals showed distinct signs of activated polyamine catabolism, e.g. overaccumulation of putrescine (three- to 17-fold), appearance of N1 -acetylspermidine and decreases in spermidine concentrations. In situ hybridization analyses revealed a marked overexpression of SSAT-specific mRNA all over the brain tissue of the transgenic animals. The transgenic animals appeared to tolerate subcutaneous injections of high-dose kainate substantially better as their overall mortality was less than 50% of that of their syngenic littermates. We used the expression of glial fibrillary acidic protein (GFAP) as a marker of brain injury in response to kainate. In situ hybridization analysis with GFAP oligonucleotide up to 7 days after the administration of sublethal kainate doses showed reduced GFAP expression in transgenic animals in comparison with their non-transgenic littermates. This difference was especially striking in the cerebral cortex of the transgenic mice where the exposure to kainate hardly induced GFAP expression. The treatment with kainate likewise resulted in loss of the hippocampal (CA3) neurons in non-transgenic but not transgenic animals. These results support our earlier findings indicating that elevated concentrations of brain putrescine, irrespective whether derived from an overexpression of ornithine decarboxylase, or as shown here, from an overexpression of SSAT, play in all likelihood a neuroprotective role in brain injury. [source]

Functional (GT)n polymorphisms in promoter region of N -methyl- d -aspartate receptor 2A subunit (GRIN2A) gene affect hippocampal and amygdala volumes

GENES, BRAIN AND BEHAVIOR, Issue 3 2010
H. Inoue
The glutamate system including N -methyl- d -aspartate (NMDA) affects synaptic formation, plasticity and maintenance. Recent studies have shown a variable (GT)n polymorphism in the promoter region of the NMDA subunit gene (GRIN2A) and a length-dependent inhibition of transcriptional activity by the (GT)n repeat. In the present study, we examined whether the GRIN2A polymorphism is associated with regional brain volume especially in medial temporal lobe structures, in which the NMDA-dependent synaptic processes have been most extensively studied. Gray matter regions of interest (ROIs) for the bilateral amygdala and hippocampus were outlined manually on the magnetic resonance images of 144 healthy individuals. In addition, voxel-based morphometry (VBM) was conducted to explore the association of genotype with regional gray matter volume from everywhere in the brain in the same sample. The manually measured hippocampal and amygdala volumes were significantly larger in subjects with short allele carriers (n = 89) than in those with homozygous long alleles (n = 55) when individual differences in intracranial volume were accounted for. The VBM showed no significant association between the genotype and regional gray matter volume in any brain region. These findings suggest that the functional GRIN2A (GT)n polymorphism could weakly but significantly impact on human medial temporal lobe volume in a length-dependent manner, providing in vivo evidence of the role of the NMDA receptor in human brain development. [source]