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Medial Septum (medial + septum)
Selected AbstractsCharacterization of the plasticity-related gene, Arc, in the frog brainDEVELOPMENTAL NEUROBIOLOGY, Issue 12 2010Lisa A. Mangiamele Abstract In mammals, expression of the immediate early gene Arc/Arg3.1 in the brain is induced by exposure to novel environments, reception of sensory stimuli, and production of learned behaviors, suggesting a potentially important role in neural and behavioral plasticity. To date, Arc has only been characterized in a few species of mammals and birds, which limits our ability to understand its role in modifying behavior. To begin to address this gap, we identified Arc in two frog species, Xenopus tropicalis and Physalaemus pustulosus, and characterized its expression in the brain of P. pustulosus. We found that the predicted protein for frog Arc shared 60% sequence similarity with Arc in other vertebrates, and we observed high Arc expression in the forebrain, but not the midbrain or hindbrain, of female túngara frogs sacrificed at breeding ponds. We also examined the time-course of Arc induction in the medial pallium, the homologue of the mammalian hippocampus, in response to a recording of a P. pustulosus mating chorus and found that accumulation of Arc mRNA peaked 0.75 h following stimulus onset. We found that the mating chorus also induced Arc expression in the lateral and ventral pallia and the medial septum, but not in the striatum, hypothalamus, or auditory midbrain. Finally, we examined acoustically induced Arc expression in response to different types of mating calls and found that Arc expression levels in the pallium and septum did not vary with the biological relevance or acoustic complexity of the signal. © 2010 Wiley Periodicals, Inc. Develop Neurobiol 70: 813,825, 2010 [source] Altered neuronal responses and regulation of neurotrophic proteins in the medial septum following fimbria-fornix transection in CNTF- and leukaemia inhibitory factor-deficient miceEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 8 2006Thomas Naumann Abstract Degeneration of axotomized GABAergic septohippocampal neurones has been shown to be enhanced in ciliary neurotrophic factor (CNTF)-deficient mice following fimbria-fornix transection (FFT), indicating a neuroprotective function of endogenous CNTF. Paradoxically, however, the cholinergic population of septohippocampal neurones was more resistant to axotomy in these mutants. As leukaemia inhibitory factor (LIF) has been identified as a potential neuroprotective factor for the cholinergic medial septum (MS) neurones, FFT-induced responses were compared in CNTF,/,, LIF,/, and CNTF/LIF double knockout mice. In CNTF,/, mice, FFT-induced cholinergic degeneration was confirmed to be attenuated as compared with wildtype mice. The expression of both LIF and LIF receptor , was increased in the MS providing a possible explanation for the enhanced neuronal resistance to FFT in these animals. However, ablation of the LIF gene also produced paradoxical effects; following FFT in LIF,/, mice no loss of GABAergic or cholinergic MS neurones was detectable during the first postlesional week, suggesting that other efficient neuroprotective mechanisms are activated in these animals. In fact, enhanced activation of astrocytes, a source of neurotrophic proteins, was indicated by increased up-regulation of glial fibrillary acidic protein and vimentin expression. In addition, mRNA levels for neurotrophin signalling components (e.g. nerve growth factor, p75NTR) were differentially regulated. The positive effect on axotomized cholinergic neurones seen in CNTF,/, and LIF,/, mice as well as the increased up-regulation of astrogliose markers was abolished in CNTF/LIF double knockout animals. Our results indicate that endogenous CNTF and LIF are involved in the regulation of neuronal survival following central nervous system lesion and are integrated into a network of neurotrophic signals that mutually influence their expression and function. [source] Endogenous histamine in the medial septum,diagonal band complex increases the release of acetylcholine from the hippocampus: a dual-probe microdialysis study in the freely moving ratEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 10 2002Lucia Bacciottini Abstract The effects of histaminergic ligands on both ACh spontaneous release from the hippocampus and the expression of c-fos in the medial septum,diagonal band (MSA-DB) of freely moving rats were investigated. Because the majority of cholinergic innervation to the hippocampus is provided by MSA-DB neurons, we used the dual-probe microdialysis technique to apply drugs to the MSA-DB and record the induced effects in the projection area. Perfusion of MSA-DB with high-KCl medium strongly stimulated hippocampal ACh release which, conversely, was significantly reduced by intra-MSA-DB administration of tetrodotoxin. Histamine or the H2 receptor agonist dimaprit, applied directly to the hippocampus, failed to alter ACh release. Conversely, perfusion of MSA-DB with these two compounds increased ACh release from the hippocampus. Also, thioperamide and ciproxifan, two H3 receptor antagonists, administered into MSA-DB, increased the release of hippocampal ACh, whereas R-,-methylhistamine, an H3 receptor agonist, produced the opposite effect. The blockade of MSA-DB H2 receptors, caused by local perfusion with the H2 receptor antagonist cimetidine, moderated the spontaneous release of hippocampal ACh and antagonized the facilitation produced by H3 receptor antagonists. Triprolidine, an H1 receptor antagonist, was without effect. Moreover, cells expressing c-fos immunoreactivity were significantly more numerous in ciproxifan- or thioperamide-treated rats than in controls, although no colocalization of anti-c-fos and anti-ChAT immunoreactivity was observed. These results indicate a role for endogenous histamine in modulating the cholinergic tone in the hippocampus. [source] 5-HT1A and NMDA receptors interact in the rat medial septum and modulate hippocampal-dependent spatial learningHIPPOCAMPUS, Issue 12 2009Elin Elvander-Tottie Abstract Cholinergic and GABAergic neurons in the medial septum/vertical limb of the diagonal band of Broca (MS/vDB) projecting to the hippocampus, constitute the septohippocampal projection, which is important for hippocampal-dependent learning and memory. There is also evidence for an extrinsic as well as an intrinsic glutamatergic network within the MS/vDB. GABAergic and cholinergic septohippocampal neurons express the serotonergic 5-HT1A receptor and most likely also glutamatergic NMDA receptors. The aim of the present study was to examine whether septal 5-HT1A receptors are important for hippocampal-dependent long-term memory and whether these receptors interact with glutamatergic NMDA receptor transmission in a manner important for hippocampal-dependent spatial memory. Intraseptal infusion of the 5-HT1A receptor agonist (R)-8-OH-DPAT (1 or 4 ,g/rat) did not affect spatial learning in the water maze task but impaired emotional memory in the passive avoidance task at the higher dose tested (4 ,g/rat). While intraseptal administration of (R)-8-OH-DPAT (4 ,g) combined with a subthreshold dose of the NMDA receptor antagonist D-AP5 (1 ,g) only marginally affected spatial acquisition, it produced a profound impairment in spatial memory. In conclusion, septal 5-HT1A receptors appears to play a more prominent role in emotional than in spatial memory. Importantly, septal 5-HT1A and NMDA receptors appear to interact in a manner, which is particularly critical for the expression or retrieval of hippocampal-dependent long-term spatial memory. It is proposed that NMDA receptor hypofunction in the septal area may unmask a negative effect of 5-HT1A receptor activation on memory, which may be clinically relevant. © 2009 Wiley-Liss, Inc. [source] Dynamic changes in the direction of the theta rhythmic drive between supramammillary nucleus and the septohippocampal systemHIPPOCAMPUS, Issue 6 2006Bernat Kocsis Abstract Neurons in the supramammillary nucleus (SUM) of urethane-anesthetized rats fire rhythmically in synchrony with hippocampal theta rhythm. As these neurons project to the septum and hippocampus, it is generally assumed that their role is to mediate ascending activation, leading to the hippocampal theta rhythm. However, the connections between SUM and the septohippocampal system are reciprocal; there is strong evidence that theta remains in the hippocampus after SUM lesions and in the SUM after lesioning the medial septum. The present study examines the dynamics of coupling between rhythmic discharge in the SUM and hippocampal field potential oscillations, using the directionality information carried by the two signals. Using directed transfer function analysis, we demonstrate that during sensory-elicited theta rhythm and also during short episodes of theta acceleration of spontaneous oscillations, the spike train of a subpopulation of SUM neurons contains information predicting future variations in rhythmic field potentials in the hippocampus. In contrast, during slow spontaneous theta rhythm, it is the SUM spike signal that can be predicted from the preceding segment of the electrical signal recorded in the hippocampus. These findings indicate that, in the anesthetized rat, SUM neurons effectively drive theta oscillations in the hippocampus during epochs of sensory-elicited theta rhythm and short episodes of theta acceleration, whereas spontaneous slow theta in the SUM is controlled by descending input from the septohippocampal system. Thus, in certain states, rhythmically firing SUM neurons function to accelerate the septal theta oscillator, and in others, they are entrained by a superordinate oscillatory network. © 2006 Wiley-Liss Inc. [source] Medial septal modulation of the ascending brainstem hippocampal synchronizing pathways in the anesthetized ratHIPPOCAMPUS, Issue 1 2006Jesse Jackson Abstract Independent and combined electrical stimulation pairings of the medial septum (MS), posterior hypothalamus (PH), and reticular pontine oralis (RPO) of the brainstem were performed in the acute urethane anesthetized rat, while recording field activity from electrodes in either the stratum oriens or stratum moleculare of the hippocampal formation. Theta frequency and power were measured during independent stimulation of each nuclei and during combined stimulation using three pairings: (1) MS,PH (2) MS,RPO and (3) PH,RPO. Each pairing consisted of parameters known to elicit theta of a high frequency for one nucleus, and parameters known to elicit a low frequency for the second nucleus. This methodology allowed us to observe whether one nucleus preferentially modulated theta activity in the hippocampus in terms of frequency and power. The MS was observed to reset theta frequency in both the upward and downward direction when stimulated in combination with either the PH (Experiment 1) or the RPO (Experiment 2). In Experiment 3 (PH,RPO), the structure receiving the higher intensity stimulation had the predominate effect on theta frequency. With MS stimulation combinations, the power of the elicited theta activity was found to increase over the independent stimulation in some cases during Experiment 1. Likewise, in Experiment 2, the combined stimulation produced a power that in most cases was significantly greater than that measured during the independent stimulations. This effect was not observed with PH and RPO stimulation combinations. The combined stimulation of the PH and RPO yielded a power similar to the independent PH stimulations. The findings support the following conclusions: (1) the major theta generating activity of the ascending brainstem synchronizing pathways involves projections from the RPO to the PH, relayed through the MS, to the hippocampal formation; and (2) that the MS directly controls theta amplitude and secondarily translates the level of ascending brainstem activity into the appropriate frequency of hippocampal theta. © 2005 Wiley-Liss, Inc. [source] Environment-spatial conditional learning in rats with selective lesions of medial septal cholinergic neuronsHIPPOCAMPUS, Issue 2 2004Agnieszka M. Janisiewicz Abstract Cholinergic medial septal neurons may regulate several aspects of hippocampal function, including place field stability and spatial working memory. Monkeys with damage to septal cholinergic neurons are impaired in visual-spatial conditional learning tasks; however, this candidate function of septal cholinergic neurons has not been studied extensively in the rat. In the present study, rats with selective lesions of cholinergic neurons in the medial septum and vertical limb of the diagonal band of Broca (MS/VDB), made with 192 IgG-saporin, were tested on a conditional associative learning task. In this task, which we term "environment-spatial" conditional learning, the correct location of a spatial response depended on the array of local environmental cues. MS/VDB-lesioned rats were impaired when the two parts of the conditional problem were presented concurrently, but not when one environment had been learned before the full conditional problem was presented. Our findings suggest that cholinergic MS/VDB neurons participate in some aspects of conditional associative learning in rats. They may also shed light on the involvement of cholinergic projections to the hippocampus in modulating and remodeling hippocampal spatial representations. © 2004 Wiley-Liss, Inc. [source] Comparison of spontaneous and septally driven hippocampal theta field and theta-related cellular activityHIPPOCAMPUS, Issue 1 2004Darren Scarlett Abstract Experiments were carried out for the purpose of comparing the electrophysiological properties of spontaneously occurring hippocampal theta field activity with those of theta-like field activity elicited by 5-Hz and 7-Hz electrical stimulation of the medial septum in urethane-anesthetized rats. Experiment 1 compared the amplitude and phase depth profiles for the three conditions of spontaneously occurring theta, theta elicited by 5-Hz medial septal stimulation, and theta elicited by 7-Hz medial septal stimulation. The results supported the conclusion that septally elicited theta field activity exhibited characteristics similar to those of spontaneously occurring theta field activity. Experiment 2 compared the discharge properties of hippocampal theta-related cellular discharges during spontaneous and septally elicited theta field activity. In contrast to the results of Experiment 1, the findings of Experiment 2 supported the conclusion that electrical stimulation of medial septal nuclei did not produce typical responses of hippocampal theta-related cellular activity. During spontaneously occurring field conditions, HPC theta-ON cells increased their discharge rates during spontaneous theta field activity, relative to LIA, and theta-OFF cells decreased (often to zero) their discharge rates during theta field activity relative to LIA. During septally elicited theta-like activity, phasic and tonic theta-ON cells decreased their discharge rates (some were totally inhibited), and most tonic theta-OFF cells increased their discharge rates (although two were totally inhibited). In addition, the discharges (albeit reduced) of the majority of both phasic and tonic theta-ON cells during septal driving became entrained to the stimulation pulses and thus exhibited rhythmicity and strong phase relations with the field activity. Furthermore, both cell types discharged near the positive peak of the septally elicited theta field activity during 5-Hz stimulation and near the negative peak during 7-Hz stimulation. The discharges of most tonic theta-OFF cells also became entrained to the stimulation pulses and exhibited similar phase relations to theta-ON cells during the 5-Hz and 7-Hz driving frequencies. Thus, based on cellular evidence, electrical stimulation of the medial septum activates the hippocampal neural circuitry involved in the generation of theta field activity in a nonphysiological manner. The findings of the present paper provide an explanation for why electrical stimulation of the medial septum in freely moving rats elicits a theta-like field activity that is dissociated from the normal behavioral correlates, in contrast to those elicited by stimulation of the posterior nucleus of the hypothalamus (Bland and Oddie. 2001. Behav Brain Res 127:119,136). © 2003 Wiley-Liss, Inc. [source] Effect of halothane on type 2 immobility-related hippocampal theta field activity and theta-on/theta-off cell dischargesHIPPOCAMPUS, Issue 1 2003Brian H. Bland Abstract Rats were studied in acute and chronic (freely moving) recording conditions during exposure to different levels of the volatile anesthetic halothane, in order to assess effects on hippocampal theta field activity in the chronic condition and on theta-related cellular discharges in the acute condition. Previous work has shown that the generation of hippocampal type 2 theta depends on the coactivation of cholinergic and GABAergic inputs from the medial septum. Based on these data and recent findings that halothane acts on interneuron GABAA receptors, we predicted that exposure of rats to subanesthetic levels would result in the induction of type 2 theta field activity. In the chronic condition, exposure to subanesthetic levels of halothane (0.5,1.0 vol %) was found to induce theta field activity during periods of immobility (type 2 theta) with a mean increase of 39% in amplitude (mV) compared to control levels during movement. The total percentage of signal power (V2) associated with peak theta frequencies (80% compared to control levels of 47%) was also increased by halothane. Over the whole range of administered halothane concentrations, theta field frequency progressively declined from a mean peak frequency of 6.5 ± 0.8 Hz at 0.5 vol % halothane to a mean peak frequency of 4.0 ± 1.8 Hz at 2.0 vol % halothane. Subsequent administration of a muscarinic cholinergic antagonist, atropine sulfate, selectively abolished all type 2 immobility-related theta field activity, while type 1 movement-related theta was still intact. At anesthetic levels (1.5,2.0 vol %) in acute experiments, hippocampal field activity spontaneously cycled between theta and large-amplitude irregular activity. Analysis of depth profiles in four experiments revealed they were identical to those previously described for rats under urethane anesthesia conditions. In addition, the discharge properties of 31 theta-related cells, classified as tonic and phasic theta-on and tonic and phasic theta-off cells, did not differ significantly from those described previously in rats anesthetized with urethane. These data provide further support for an involvement of GABAA receptors in the generation of hippocampal theta. Hippocampus 2003;13:38,47. © 2003 Wiley-Liss, Inc. [source] Silencing of choline acetyltransferase expression by lentivirus-mediated RNA interference in cultured cells and in the adult rodent brainJOURNAL OF NEUROSCIENCE RESEARCH, Issue 2 2009Julie Santamaria Abstract RNA interference (RNAi) is a potent mechanism for local silencing of gene expression and can be used to study loss-of-function phenotypes in mammalian cells. We used RNAi to knockdown specifically the expression of choline acetyltransferase (ChAT), the enzyme of acetylcholine biosynthesis, both in cultured cells and in the adult brain. We first identified a 19-nucleotide sequence in the coding region of rat and mouse ChAT transcripts that constitutes a target for potent silencing of ChAT expression by RNAi. We generated a lentiviral vector that produces both a small hairpin RNA (shRNA) targeting ChAT mRNAs and the enhanced green fluorescent protein (EGFP) reporter protein to facilitate identification of transduced cells. In the cholinergic cell line NG108-15, there was at least 90% less of the ChAT protein, as measured by assaying its enzymatic activity, 3 days postinfection with this vector than in cells infected with a control vector. The vector was used to transduce cholinergic neurons in vivo and reduced ChAT expression strongly and specifically in the cholinergic neurons of the medial septum in adult rats, without affecting the expression of the vesicular acetylcholine transporter. This lentiviral vector is thus a powerful tool for specific inactivation of cholinergic neurotransmission and can therefore be used to study the role of cholinergic nuclei in the brain. This lentiviral-mediated RNAi approach will also allow the development of new animal models of diseases in which cholinergic neurotransmission is specifically altered. © 2008 Wiley-Liss, Inc. [source] | ||||||||||