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Voltage-dependent Calcium Channels (voltage-dependent + calcium_channel)
Selected AbstractsThe P/Q-type voltage-dependent calcium channel: a therapeutic target in spinocerebellar ataxia type 6ACTA NEUROLOGICA SCANDINAVICA, Issue 5 2007J. Gazulla Background,,, Voltage-dependent calcium channels (VDCCs) are heteromultimeric complexes that mediate calcium influx into cells; the ,1A subunit is the pore-forming subunit specific to the neuronal P/Q-type VDCCs. Spinocerebellar ataxia type 6 (SCA 6) is caused by an abnormal expansion of a CAG repeat in CACNA1A, which encodes the ,1A subunit. Heterologous expression of mutated ,1A subunits resulted in increased channel inactivation in electrophysiological tests. Gabapentin and pregabalin interact with the ,2, subunit of the VDCCs and improved ataxia in cases of cortical cerebellar atrophy (CCA) and ataxia-telangiectasia. Materials and methods,,, A bibliographical review was performed in order to find out if gabapentin and pregabalin coud prove useful in the treatment of SCA 6. Results,,, Gabapentin and pregabalin slowed the rate of inactivation in recombinant P/Q-type VDCCs. SCA 6 shares neuropathological findings with CCA. Conclusions,,, On the basis of the neuropathological identity of SCA 6 with CCA, and of the effect of gabapentin and pregabalin on recombinant VDCCs the authors put forward the hypothesis that these drugs might prove beneficial in SCA 6, as the ataxia would be expected to improve. The authors hope that researchers working with this illness will be encouraged to undertake the appropriate clinical and experimental work. [source] Genetic and pharmacological studies of GluR5 modulation of inhibitory synaptic transmission in the anterior cingulate cortex of adult miceDEVELOPMENTAL NEUROBIOLOGY, Issue 2 2007Long-Jun Wu Abstract In the anterior cingulate cortex (ACC), GluR5-containing kainate receptor mediated the small portion of excitatory postsynaptic current. However, little is known about its role in modulation of neurotransmitter release in this brain region. In the present study, we address this question by using selective GluR5 agonist and antagonist, as well as GluR5,/, mice. Our results showed that activation of GluR5 induced action potential-dependent GABA release, which is also required for the activation of voltage-dependent calcium channel and Ca2+ influx. The effect of GluR5 activation is selective to the GABAergic, but not glutamatergic synaptic transmission. Endogenous activation of GluR5 also enhanced GABA release to ACC pyramidal neurons and the corresponding postsynaptic tonic GABA current. Our results suggest the somatodendritic, but not presynaptic GluR5, in modulation of GABA release. The endogenous GluR5 activation and the subsequent tonic GABA current may play an inhibitory role in ACC-related brain functions. © 2006 Wiley Periodicals, Inc. Develop Neurobiol 67: 146,157, 2007. [source] Effects of hyperventilation on fast goal-directed limb movements in spinocerebellar ataxia type 6EUROPEAN JOURNAL OF NEUROLOGY, Issue 5 2001M.-U. Manto It has been shown previously that hyperventilation modifies the features of the nystagmus in cerebellar patients (Walker and Zee, 1999). It has been hypothesized that hyperventilation influences the oculomotor control through a metabolic effect on cerebellar calcium channels, which play a critical role in the firing behaviour of neuronal populations in the cerebellum. This hypothesis has been tested here by analysing fast goal-directed limb movements before and after hyperventilation in spinocerebellar ataxia type 6 (SCA-6), a disease associated with a polyglutamine expansion in the , 1-A voltage-dependent calcium channel. Cerebellar hypermetria associated with fast distal single-joint movements was found to be increased following hyperventilation in patients presenting SCA-6 but remained unchanged in patients with idiopathic late-onset cerebellar degeneration (ILOCA). This is a new provocative test to enhance distal dysmetria in SCA-6. The present results strengthen the hypothesis of Walker and Zee. It is suggested that hyperventilation enhances the defective calcium transfers in SCA-6, resulting in an impairment of the calcium influx in particular into Purkinje cells involved in the control of fast goal-directed voluntary movements. [source] Increased CaV,1a expression with aging contributes to skeletal muscle weaknessAGING CELL, Issue 5 2009Jackson R. Taylor Summary Ca2+ release from the sarcoplasmic reticulum (SR) into the cytosol is a crucial part of excitation,contraction (E-C) coupling. Excitation,contraction uncoupling, a deficit in Ca2+ release from the SR, is thought to be responsible for at least some of the loss in specific force observed in aging skeletal muscle. Excitation,contraction uncoupling may be caused by alterations in expression of the voltage-dependent calcium channel ,1s (CaV1.1) and ,1a (CaV,1a) subunits, both of which are necessary for E-C coupling to occur. While previous studies have found CaV1.1 expression declines in old rodents, CaV,1a expression has not been previously examined in aging models. Western blot analysis shows a substantial increase of CaV,1a expression over the full lifespan of Friend Virus B (FVB) mice. To examine the specific effects of CaV,1a overexpression, a CaV,1a -YFP plasmid was electroporated in vivo into young animals. The resulting increase in expression of CaV,1a corresponded to decline of CaV1.1 over the same time period. YFP fluorescence, used as a measure of CaV,1a -YFP expression in individual fibers, also showed an inverse relationship with charge movement, measured using the whole-cell patch-clamp technique. Specific force was significantly reduced in young CaV,1a -YFP electroporated muscle fibers compared with sham-electroporated, age-matched controls. siRNA interference of CaV,1a in young muscles reduced charge movement, while charge movement in old was restored to young control levels. These studies imply CaV,1a serves as both a positive and negative regulator CaV1.1 expression, and that endogenous overexpression of CaV,1a during old age may play a role in the loss of specific force. [source] ,Protective premedication': an option with gabapentin and related drugs?ACTA ANAESTHESIOLOGICA SCANDINAVICA, Issue 9 2004A review of gabapentin, pregabalin in the treatment of post-operative pain Substantial progress has been made during the last decades in our understanding of acute pain mechanisms, and this knowledge has encouraged the search for novel treatments. Of particular interest has been the observation that tissue injury initiates a number of modulations of both the peripheral and the central pain pathways, which convert the system from a ,physiological' to a ,pathological' mode of processing afferent information. Gabapentin, which binds to the ,2, subunit of the voltage-dependent calcium channel, is active in animal models of ,pathological' but not in models of ,physiological' pain. Consequently, attention has so far been focused on neuropathic pain as a target for the clinical use of gabapentin and analogues. Recently, several reports have indicated that gabapentin may have a place in the treatment of post-operative pain. This article presents a brief summary of the potential mechanisms of post-operative pain, and a systematic review of the available data of gabapentin and pregabalin for post-operative analgesia. It is concluded that the results with gabapentin and pregabalin in post-operative pain treatment published so far are promising. It is suggested that future studies should explore the effects of ,protective premedication' with combinations of various antihyperalgesic and analgesic drugs for post-operative analgesia. [source] Scutellarin-induced endothelium-independent relaxation in rat aortaPHYTOTHERAPY RESEARCH, Issue 11 2008Zhenwei Pan Abstract Scutellarin is a flavonoid extracted from the traditional Chinese herb, Erigeron breviscapus Hand Mazz. In the present study, the vasorelaxant effects of scutellarin and the underlying mechanism were investigated in isolated rat aorta. Scutellarin (3, 10, 30, 100 µm) caused a dose-dependent relaxation in both endothelium-intact and endothelium-denuded rat aortic rings precontracted with noradrenaline bitartrate (IC50 = 7.7 ± 0.6 µm), but not with potassium chloride. Tetraethylammonium, glibenclamide, atropine, propranolol, indomethacin and N(G)-nitro- l -arginine methyl ester had no influence on the vasorelaxant effect of scutellarin, which further excluded the involvement of potassium channels, muscarinic receptor, nitric oxide pathway and prostaglandin in this effect. Pretreatment with scutellarin decreased the tonic phase, but not the phasic phase of the noradrenaline bitartrate induced tension increment. Scutellarin also alleviated Ca2+ -induced vasoconstriction in Ca2+ -depleted/noradrenaline bitartrate pretreated rings in the presence of voltage-dependent calcium channel blocker verapamil. The noradrenaline bitartrate evoked intracellular calcium increase was inhibited by scutellarin. Scutellarin had no effect on phorbol-12,13-diacetate induced contraction in a calcium-free bath solution. These results showed that scutellarin could relax thoracic artery rings in an endothelium-independent manner. The mechanism seems to be the inhibition of extracellular calcium influx independent of the voltage-dependent calcium channel. Copyright © 2008 John Wiley & Sons, Ltd. [source] Modulation of ACh release by presynaptic muscarinic autoreceptors in the neuromuscular junction of the newborn and adult ratEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 1 2003Manel M. Santafé Abstract We studied the presynaptic muscarinic autoreceptor subtypes controlling ACh release and their relationship with voltage-dependent calcium channels in the neuromuscular synapses of the Levator auris longus muscle from adult (30,40 days) and newborn (3,6 and 15 days postnatal) rats. Using intracellular recording, we studied how several muscarinic antagonists affected the evoked endplate potentials. In some experiments we previously incubated the muscle with calcium channel blockers (nitrendipine, ,-conotoxin-GVIA and ,-Agatoxin-IVA) before determining the muscarinic response. In the adult, the M1 receptor-selective antagonist pirenzepine (10 µm) reduced evoked neurotransmission (, 47%). The M2 receptor-selective antagonist methoctramine (1 µm) increased the evoked release (, 67%). Both M1- and M2-mediated mechanisms depend on calcium influx via P/Q-type synaptic channels. We found nothing to indicate the presence of M3 (4-DAMP-sensitive) or M4 (tropicamide-sensitive) receptors in the muscles of adult or newborn rats. In the 3,6-day newborn rats, pirenzepine reduced the evoked release (, 30%) by a mechanism independent of L-, N- and P/Q-type calcium channels, and the M2 antagonist methoctramine (1 µm) unexpectedly decreased the evoked release (, 40%). This methoctramine effect was a P/Q-type calcium-channel-dependent mechanism. However, upon maturation in the first two postnatal weeks, the M2 pathway shifted to perform the calcium-dependent release-inhibitory activity found in the adult. We show that the way in which M1 and M2 muscarinic receptors modulate neurotransmission can differ between the developing and adult rat neuromuscular synapse. [source] Calcium and polyamine regulated calcium-sensing receptors in cardiac tissuesFEBS JOURNAL, Issue 12 2003Rui Wang Activation of a calcium-sensing receptor (Ca-SR) leads to increased intracellular calcium concentration and altered cellular activities. The expression of Ca-SR has been identified in both nonexcitable and excitable cells, including neurons and smooth muscle cells. Whether Ca-SR was expressed and functioning in cardiac myocytes remained unclear. In the present study, the transcripts of Ca-SR were identified in rat heart tissues using RT-PCR that was further confirmed by sequence analysis. Ca-SR proteins were detected in rat ventricular and atrial tissues as well as in isolated cardiac myocytes. Anti-(Ca-SR) Ig did not detect any specific bands after preadsorption with standard Ca-SR antigens. An immunohistochemistry study revealed the presence of Ca-SR in rat cardiac as well as other tissues. An increase in extracellular calcium or gadolinium induced a concentration-dependent sustained increase in [Ca2+]i in isolated ventricular myocytes from adult rats. Spermine (1,10 mm) also increased [Ca2+]i. Pre-treatment of cardiac myocytes with thapsigargin or U73122 abolished the extracellular calcium, gadolinium or spermine-induced increase in [Ca2+]i. The blockade of Na+/Ca2+ exchanger or voltage-dependent calcium channels did not alter the extracellular calcium-induced increase in [Ca2+]i. Finally, extracellular calcium, gadolinium and spermine all increased intracellular inositol 1,4,5-triphosphate (IP3) levels. Our results demonstrated that Ca-SR was expressed in cardiac tissue and cardiomyocytes and its function was regulated by extracellular calcium and spermine. [source] Corticosterone shifts different forms of synaptic potentiation in opposite directionsHIPPOCAMPUS, Issue 6 2005Harm J. Krugers Abstract Calcium entering the cell via different routes, e.g.,N -methyl- D -aspartate (NMDA) receptors or voltage-dependent calcium channels (VDCCs), plays a pivotal role in hippocampal synaptic potentiation. Since corticosteroid hormones have been reported to enhance calcium influx through VDCCs, one may predict that these hormones facilitate hippocampal synaptic efficacy. Surprisingly, though, stress and corticosteroids have so far been found to reduce synaptic potentiation. Here, we addressed this apparent paradox and examined synaptic potentiation in the CA1 area of hippocampal slices from mice with low basal corticosterone levels 1,4 h after a brief in vitro administration of corticosterone. Nifedipine and APV were used to isolate NMDA receptor-mediated and VDCC-mediated long-term potentiations (LTPs), respectively. We report that corticosterone facilitates synaptic potentiation that depends on activation of VDCCs while impairing synaptic plasticity that is mediated by NMDA receptor activation. The glucocorticoid-receptor (GR) antagonist RU 38486 blocked both the effects of corticosterone. These results indicate that the net effect of corticosteroid hormones on synaptic plasticity is determined by the balance between different types of potentiation, a balance that may be region specific and depends on the experimental conditions. We speculate that these opposite effects on synaptic efficacy are involved in the bidirectional modulation of cognitive performance by corticosteroid hormones. © 2005 Wiley-Liss, Inc. [source] Contribution of T-type VDCC to TEA-induced long-term synaptic modification in hippocampal CA1 and dentate gyrusHIPPOCAMPUS, Issue 5 2002Dong Song Abstract We have previously reported that exposure to the K+ channel blocker tetraethylammonium (TEA), 25 mM, induces long-term potentiation (LTP) in CA1, but not in the dentate gyrus (DG), of the rat hippocampal slice. During TEA application, stimulation of excitatory afferents results in a strong depolarizing potential after the fast excitatory postsynaptic potential (EPSP) in CA1, but not in DG. We hypothesized that the differential effect of TEA on long-term synaptic modification in CA1 and DG results from different levels of TEA-elicited depolarization in the two cell types. Additional pharmacological studies showed that blockade of T-type voltage-dependent calcium channels (VDCCs) decreased both the magnitude of LTP and the late, depolarizing potential in CA1. Blockade of L-type VDCCs had no such effect. Using computer models of morphologically reconstructed CA1 pyramidal cells and DG granule cells, we tested our hypothesis by simulating the relative intracellular Ca2+ accumulation and membrane potential changes mediated by T-type and L-type VDCCs. Simulation results using pyramidal cell models showed that, with decreased maximum conductance of TEA-sensitive potassium channels, synaptic inputs elicited strong depolarizing potentials similar to those observed with intracellular recording. During this depolarization, VDCCs were opened and resulted in a large intracellular Ca2+ accumulation that presumably caused LTP. When T-type VDCCs were blocked, the magnitudes of both the Ca2+ accumulation and the late depolarizing potential were decreased substantially. Simulated blockade of L-type VDCCs had only a minor effect. Together, our modeling and experimental studies indicate that T-type VDCCs, rather than L-type VDCCs, are primarily responsible for facilitating the depolarizing potential caused by TEA and for the consequent Ca2+ influx. Thus, our findings strongly suggest that the induction of TEA-LTP in CA1 depends primarily on T-type, rather than L-type, VDCCs. Simulation results using modeled granule cells suggests that the failure of TEA to induce LTP in DG is partly due to a low density of T-type VDCCs in granule cell membranes. Hippocampus 2002;12:689,697. © 2002 Wiley-Liss, Inc. [source] Evidence of calcium- and SNARE-dependent release of CuZn superoxide dismutase from rat pituitary GH3 cells and synaptosomes in response to depolarizationJOURNAL OF NEUROCHEMISTRY, Issue 3 2007Mariarosaria Santillo Abstract The antioxidant enzyme CuZn superoxide dismutase (SOD1) is secreted by many cell lines. However, it is not clear whether SOD1 secretion is only constitutive or can be regulated in an activity-dependent fashion. Using rat pituitary GH3 cells that express voltage-dependent calcium channels and are subjected to Ca2+ oscillations, we found that treatment with high K+ -induced SOD1 release that was significantly higher than the constitutive secretion. Evoked SOD1 release was correlated with depolarization-dependent calcium influx and was virtually abolished by removal of extracellular calcium with EGTA or by pre-incubation of GH3 cells with Botulinum toxin A that cleaves the SNARE protein SNAP-25. Immunofluorescence experiments performed in GH3 cells and rat brain synaptosomes showed that K+ -depolarization induced a marked depletion of intracellular SOD1 immunoreactivity, an effect that was again abolished in the absence of extracellular calcium or after treatment with Botulinum toxin A. Subcellular fractionation analysis showed that SOD1 was present in large dense core vesicles. These data clearly show that, in addition to the constitutive SOD1 secretion, depolarization induces an additional rapid calcium-dependent SOD1 release in GH3 cells and in rat brain synaptosomes. This likely occurs through exocytosis from SOD1-containing vesicles operated by the SNARE complex. [source] Substance P initiates NFAT-dependent gene expression in spinal neuronsJOURNAL OF NEUROCHEMISTRY, Issue 2 2006V. S. Seybold Abstract Persistent hyperalgesia is associated with increased expression of proteins that contribute to enhanced excitability of spinal neurons, however, little is known about how expression of these proteins is regulated. We tested the hypothesis that Substance P stimulation of neurokinin receptors on spinal neurons activates the transcription factor nuclear factor of activated T cells isoform 4 (NFATc4). The occurrence of NFATc4 in spinal cord was demonstrated with RT-PCR and immunocytochemistry. Substance P activated NFAT-dependent gene transcription in primary cultures of neonatal rat spinal cord transiently transfected with a luciferase DNA reporter construct. The effect of Substance P was mediated by neuronal neurokinin-1 receptors that coupled to activation of protein kinase C, l -type voltage-dependent calcium channels, and calcineurin. Interestingly, Substance P had no effect on cyclic AMP response element (CRE)-dependent gene expression. Conversely, calcitonin gene-related peptide, which activated CRE-dependent gene expression, did not activate NFAT signaling. These data provide evidence that peptides released from primary afferent neurons regulate discrete patterns of gene expression in spinal neurons. Because the release of Substance P and calcitonin gene-related peptide from primary afferent neurons is increased following peripheral injury, these peptides may differentially regulate the expression of proteins that underlie persistent hyperalgesia. [source] Involvement of brain-derived neurotrophic factor (BDNF) in the functional elimination of synaptic contacts at polyinnervated neuromuscular synapses during developmentJOURNAL OF NEUROSCIENCE RESEARCH, Issue 7 2010N. Garcia Abstract We use immunohistochemistry to describe the localization of brain-derived neurotrophic factor (BDNF) and its receptors trkB and p75NTR in the neuromuscular synapses of postnatal rats (P6,P7) during the synapse elimination period. The receptor protein p75NTR is present in the nerve terminal, muscle cell and glial Schwann cell whereas BDNF and trkB proteins can be detected mainly in the pre- and postsynaptic elements. Exogenously applied BDNF (10 nM for 3 hr or 50 nM for 1 hr) increases ACh release from singly and dually innervated synapses. This effect may be specific for BDNF because the neurotrophin NT-4 (2,8 nM) does not modulate release at P6,P7. Blocking the receptors trkB and p75NTR (with K-252a and anti-p75-192-IgG, respectively) completely abolishes the potentiating effect of exogenous BDNF. In addition, exogenous BDNF transiently recruits functionally depressed silent terminals, and this effect seems to be mediated by trkB. Calcium ions, the L-type voltage-dependent calcium channels and protein kinase C are involved in BDNF-mediated nerve ending recruitment. Blocking experiments suggest that endogenous BDNF could operate through p75NTR receptors coupled to potentiate ACh release in all nerve terminals because the anti-p75-192-IgG reduces release. However, blocking the trkB receptor (K-252a) or neutralizing endogenous BDNF with the trkB-IgG fusion protein reveals a trkB-mediated release inhibition on almost mature strong endings in dual junctions. Taken together these results suggest that a BDNF-induced p75NTR -mediated ACh release potentiating mechanism and a BDNF-induced trkB-mediated release inhibitory mechanism may contribute to developmental synapse disconnection. © 2009 Wiley-Liss, Inc. [source] Modulation of calcium entry and glutamate release in cultured cerebellar granule cells by palytoxinJOURNAL OF NEUROSCIENCE RESEARCH, Issue 8 2006Carmen Vale Abstract A channel open on the membrane can be formed by palytoxin (PTX). Ten nanomolar PTX caused an irreversible increase in the cytosolic calcium concentration ([Ca2+]c), which was abolished in the absence of external calcium. The increase was eliminated by saxitoxin (STX) and nifedipine (NIF). Calcium rise is secondary to the membrane depolarization. PTX effect on calcium was dependent on extracellular Na+. Li+ decreased the PTX-evoked rise in [Ca2+]c; replacement of Na+ by N-methyl-D-glucamine (NMDG) abolished PTX-induced calcium increase. [Ca2+]c increase by PTX was strongly reduced after inhibition of the reverse operation of the Na+/Ca2+ exchanger, in the presence of antagonists of excitatory amino acid (EAA) receptors, and by inhibition of neurotransmitter release. PTX did not modify calcium extrusion by the plasma membrane Ca2+ -ATPase (PMCA), because blockade of the calcium pump increased rather than decreased the PTX-induced calcium influx. Extracellular levels of glutamate and aspartate were measured by HPLC and exocytotic neurotransmitter release by determination of synaptic vesicle exocytosis using total internal reflection fluorescence microscopy (TIRFM). PTX caused a concentration-dependent increase in EAA release to the culture medium. Ten nanomolar PTX decreased cell viability by 30% within 5 min. PTX-induced calcium influx involves three pathways: Na+ -dependent activation of voltage-dependent sodium channels (VDSC) and voltage-dependent calcium channels (VDCC), reverse operation of the Na+/Ca2+ exchanger, and indirect activation of EAA receptors through glutamate release. The neuronal injury produced by the toxin could be partially mediated by the PTX-induced overactivation of EAA receptors, VDSC, VDCC and the glutamate efflux into the extracellular space. © 2006 Wiley-Liss, Inc. [source] Seizures, enhanced excitation, and increased vesicle number in Lis1 mutant mice,ANNALS OF NEUROLOGY, Issue 5 2009Joel S.F. Greenwood PhD Objective In humans, abnormal neuronal migration and severe neuronal disorganization resulting from Lis1 (lissencephaly) haploinsufficiency contributes to cognitive impairment and seizures early in life. In Lis1 heterozygotic mice, severe hippocampal disorganization and cognitive impairment have also been reported. Using this mouse model, we examined the functional impact of LIS1 deficiency with particular focus on excitatory glutamate-mediated synaptic transmission. Methods We used visualized patch-clamp recordings in acute hippocampal slices. We recorded spontaneous, miniature and stimulation-evoked excitatory postsynaptic current (EPSC). Additional mice were processed for immunohistochemistry, electron microscopy (EM), or video-electroencephalographic (EEG) monitoring. Results Video-EEG confirmed the presence of spontaneous electrographic seizures in Lis1 mutant mice. In disorganized hippocampal slices from Lis1+/, mice, we noted a nearly two-fold significant increase in the frequency of spontaneous and miniature EPSC; no significant change in amplitude or decay was noted. Synaptic function assessed using brief repetitive or paired-pulse stimulation protocols, also revealed significant enhancement of glutamate-mediated excitation. Low concentrations of cadmium, a nonspecific blocker of voltage-dependent calcium channels mediating vesicle release, effectively restored paired-pulse facilitation deficits back to control levels. Analysis of synapse ultrastructure at the EM level identified a large increase in synaptic vesicle number. Interpretation Seizure activity, possibly associated with increased glutamate-mediated excitation and an increased pool of vesicles at the presynaptic site, was demonstrated in a mouse model of type I lissencephaly. Ann Neurol 2009;66:644,653 [source] Role of n-type voltage-dependent calcium channels in autoimmune optic neuritis,ANNALS OF NEUROLOGY, Issue 1 2009Ivana Gadjanski PhD Objective The aim of this study was to investigate the role of voltage-dependent calcium channels (VDCCs) in axon degeneration during autoimmune optic neuritis. Methods Calcium ion (Ca2+) influx into the optic nerve (ON) through VDCCs was investigated in a rat model of optic neuritis using manganese-enhanced magnetic resonance imaging and in vivo calcium imaging. After having identified the most relevant channel subtype (N-type VDCCs), we correlated immunohistochemistry of channel expression with ON histopathology. In the confirmatory part of this work, we performed a treatment study using ,-conotoxin GVIA, an N-type specific blocker. Results We observed that pathological Ca2+ influx into ONs during optic neuritis is mediated via N-type VDCCs. By analyzing the expression of VDCCs in the inflamed ONs, we detected an upregulation of ,1B, the pore-forming subunit of N-type VDCCs, in demyelinated axons. However, high expression levels were also found on macrophages/activated microglia, and lower levels were detected on astrocytes. The relevance of N-type VDCCs for inflammation-induced axonal degeneration and the severity of optic neuritis was corroborated by treatment with ,-conotoxin GVIA. This blocker led to decreased axon and myelin degeneration in the ONs together with a reduced number of macrophages/activated microglia. These protective effects were confirmed by analyzing the spinal cords of the same animals. Interpretation We conclude that N-type VDCCs play an important role in inflammation-induced axon degeneration via two mechanisms: First, they directly mediate toxic Ca2+ influx into the axons; and second, they contribute to macrophage/microglia function, thereby promoting secondary axonal damage. Ann Neurol 2009;66:81,93 [source] KMUP-1 activates BKCa channels in basilar artery myocytes via cyclic nucleotide-dependent protein kinasesBRITISH JOURNAL OF PHARMACOLOGY, Issue 6 2005Bin-Nan Wu This study investigated whether KMUP-1, a synthetic xanthine-based derivative, augments the delayed-rectifier potassium (KDR)- or large-conductance Ca2+ -activated potassium (BKCa) channel activity in rat basilar arteries through protein kinase-dependent and -independent mechanisms. Cerebral smooth muscle cells were enzymatically dissociated from rat basilar arteries. Conventional whole cell, perforated and inside-out patch-clamp electrophysiology was used to monitor K+ - and Ca2+ channel activities. KMUP-1 (1 ,M) had no effect on the KDR current but dramatically enhanced BKCa channel activity. This increased BKCa current activity was abolished by charybdotoxin (100 nM) and iberiotoxin (100 nM). Like KMUP-1, the membrane-permeable analogs of cGMP (8-Br-cGMP) and cAMP (8-Br-cAMP) enhanced the BKCa current. BKCa current activation by KMUP-1 was markedly inhibited by a soluble guanylate cyclase inhibitor (ODQ 10 ,M), an adenylate cyclase inhibitor (SQ 22536 10 ,M), competitive antagonists of cGMP and cAMP (Rp-cGMP, 100 ,M and Rp-cAMP, 100 ,M), and cGMP- and cAMP-dependent protein kinase inhibitors (KT5823, 300 nM and KT5720, 300 nM). Voltage-dependent L-type Ca2+ current was significantly suppressed by KMUP-1 (1 ,M), and nearly abolished by a calcium channel blocker (nifedipine, 1 ,M). In conclusion, KMUP-1 stimulates BKCa currents by enhancing the activity of cGMP-dependent protein kinase, and in part this is due to increasing cAMP-dependent protein kinase. Physiologically, this activation would result in the closure of voltage-dependent calcium channels and the relaxation of cerebral arteries. British Journal of Pharmacology (2005) 146, 862,871. doi:10.1038/sj.bjp.0706387 [source] | |||||||||||||