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Mayo S, Gómez-Manjón I, Marco-Hernández AV, Fernández-Martínez FJ, Camacho A, Martínez F. N-Type Ca Channel in Epileptic Syndromes and Epilepsy: A Systematic Review of Its Genetic Variants. Int J Mol Sci 2023; 24:6100. [PMID: 37047073 PMCID: PMC10094502 DOI: 10.3390/ijms24076100] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2023] [Revised: 03/20/2023] [Accepted: 03/22/2023] [Indexed: 04/14/2023] Open
Abstract
N-type voltage-gated calcium channel controls the release of neurotransmitters from neurons. The association of other voltage-gated calcium channels with epilepsy is well-known. The association of N-type voltage-gated calcium channels and pain has also been established. However, the relationship between this type of calcium channel and epilepsy has not been specifically reviewed. Therefore, the present review systematically summarizes existing publications regarding the genetic associations between N-type voltage-dependent calcium channel and epilepsy.
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Affiliation(s)
- Sonia Mayo
- Genetics and Inheritance Research Group, Instituto de Investigación Sanitaria Hospital 12 de Octubre, 28041 Madrid, Spain
- Department of Genetics, Hospital Universitario 12 de Octubre, 28041 Madrid, Spain
| | - Irene Gómez-Manjón
- Genetics and Inheritance Research Group, Instituto de Investigación Sanitaria Hospital 12 de Octubre, 28041 Madrid, Spain
- Department of Genetics, Hospital Universitario 12 de Octubre, 28041 Madrid, Spain
| | - Ana Victoria Marco-Hernández
- Neuropediatric Unit, Hospital Universitario Doctor Peset, 46017 Valencia, Spain
- Translational Research in Genetics, Instituto de Investigación Sanitaria La Fe, 46026 Valencia, Spain
| | - Francisco Javier Fernández-Martínez
- Genetics and Inheritance Research Group, Instituto de Investigación Sanitaria Hospital 12 de Octubre, 28041 Madrid, Spain
- Department of Genetics, Hospital Universitario 12 de Octubre, 28041 Madrid, Spain
| | - Ana Camacho
- Division of Pediatric Neurology, Department of Neurology, Hospital Universitario 12 de Octubre, Universidad Complutense de Madrid, 28040 Madrid, Spain
| | - Francisco Martínez
- Translational Research in Genetics, Instituto de Investigación Sanitaria La Fe, 46026 Valencia, Spain
- Genomic Unit, Instituto de Investigación Sanitaria La Fe, 46026 Valencia, Spain
- Genetics Unit, Hospital Universitario y Politecnico La Fe, 46026 Valencia, Spain
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Akinfiresoye LR, Newton J, Suman S, Datta K, N'Gouemo P. Targeted Inhibition of Upregulated Sodium-Calcium Exchanger in Rat Inferior Colliculus Suppresses Alcohol Withdrawal Seizures. Mol Neurobiol 2023; 60:292-302. [PMID: 36264435 PMCID: PMC10577795 DOI: 10.1007/s12035-022-03072-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/08/2022] [Accepted: 10/08/2022] [Indexed: 11/29/2022]
Abstract
The inferior colliculus (IC) is critical in initiating acoustically evoked alcohol withdrawal-induced seizures (AWSs). Recently, we reported that systemic inhibition of Ca2+ entry via the reverse mode activity of the Na+/Ca2+ exchanger (NCXrev) suppressed AWSs, suggesting remodeling of NCX expression and function, at least in the IC, the site of AWS initiation. Here, we probe putative changes in protein expression in the IC of NCX isoforms, including NCX type 1 (NCX1), 2 (NCX2), and 3 (NCX3). We also evaluated the efficacy of targeted inhibition of NCX1rev and NCX3rev activity in the IC on the occurrence and severity of AWSs using SN-6 and KB-R943, respectively. We used our well-characterized alcohol intoxication/withdrawal model associated with enhanced AWS susceptibility. IC tissues from the alcohol-treated group were collected 3 h (before the onset of AWS susceptibility), 24 h (when AWS susceptibility is maximal), and 48 h (when AWS susceptibility is resolved) following alcohol withdrawal; in comparison, IC tissues from the control-treated group were collected at 24 h after the last gavage. Analysis shows that NCX1 protein levels were markedly higher 3 and 24 h following alcohol withdrawal. However, NCX3 protein levels were only higher 3 h following alcohol withdrawal. The analysis also reveals that bilateral microinjections of SN-6 (but not KB-R7943) within the IC markedly suppressed the occurrence and severity of AWSs. Together, these findings indicate that NCX1 is a novel molecular target that may play an essential role in the pathogenesis and pathophysiology of AWSs.
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Affiliation(s)
- Luli R Akinfiresoye
- Department of Physiology and Biophysics, Howard University College of Medicine, Suite 2420, 520 W Street, NW, Washington, DC, 20059, USA
- Diversion Control Division, Drug Enforcement Administration, United States Department of Justice, Springfield, VA, USA
| | - Jamila Newton
- Department of Physiology and Biophysics, Howard University College of Medicine, Suite 2420, 520 W Street, NW, Washington, DC, 20059, USA
- California State University, Stanislaus, Turlock, CA, USA
| | - Shubhankar Suman
- Oncology and Department of Biochemistry and Molecular & Cellular Biology, Georgetown Lombardi Comprehensive Cancer Center (LCCC), Washington, DC, USA
| | - Kamal Datta
- Oncology and Department of Biochemistry and Molecular & Cellular Biology, Georgetown Lombardi Comprehensive Cancer Center (LCCC), Washington, DC, USA
| | - Prosper N'Gouemo
- Department of Physiology and Biophysics, Howard University College of Medicine, Suite 2420, 520 W Street, NW, Washington, DC, 20059, USA.
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Bordia T, Zahr NM. The Inferior Colliculus in Alcoholism and Beyond. Front Syst Neurosci 2020; 14:606345. [PMID: 33362482 PMCID: PMC7759542 DOI: 10.3389/fnsys.2020.606345] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Accepted: 11/02/2020] [Indexed: 12/28/2022] Open
Abstract
Post-mortem neuropathological and in vivo neuroimaging methods have demonstrated the vulnerability of the inferior colliculus to the sequelae of thiamine deficiency as occurs in Wernicke-Korsakoff Syndrome (WKS). A rich literature in animal models ranging from mice to monkeys-including our neuroimaging studies in rats-has shown involvement of the inferior colliculi in the neural response to thiamine depletion, frequently accomplished with pyrithiamine, an inhibitor of thiamine metabolism. In uncomplicated alcoholism (i.e., absent diagnosable neurological concomitants), the literature citing involvement of the inferior colliculus is scarce, has nearly all been accomplished in preclinical models, and is predominately discussed in the context of ethanol withdrawal. Our recent work using novel, voxel-based analysis of structural Magnetic Resonance Imaging (MRI) has demonstrated significant, persistent shrinkage of the inferior colliculus using acute and chronic ethanol exposure paradigms in two strains of rats. We speculate that these consistent findings should be considered from the perspective of the inferior colliculi having a relatively high CNS metabolic rate. As such, they are especially vulnerable to hypoxic injury and may be provide a common anatomical link among a variety of disparate insults. An argument will be made that the inferior colliculi have functions, possibly related to auditory gating, necessary for awareness of the external environment. Multimodal imaging including diffusion methods to provide more accurate in vivo visualization and quantification of the inferior colliculi may clarify the roles of brain stem nuclei such as the inferior colliculi in alcoholism and other neuropathologies marked by altered metabolism.
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Affiliation(s)
- Tanuja Bordia
- Neuroscience Program, SRI International, Menlo Park, CA, United States
| | - Natalie M. Zahr
- Neuroscience Program, SRI International, Menlo Park, CA, United States
- Department of Psychiatry and Behavioral Sciences, Stanford University School of Medicine, Stanford, CA, United States
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Newton J, Suman S, Akinfiresoye LR, Datta K, Lovinger DM, N'Gouemo P. Alcohol withdrawal upregulates mRNA encoding for Ca V2.1-α1 subunit in the rat inferior colliculus. Alcohol 2018; 66:21-26. [PMID: 29277284 DOI: 10.1016/j.alcohol.2017.07.007] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2017] [Revised: 07/17/2017] [Accepted: 07/18/2017] [Indexed: 10/18/2022]
Abstract
We previously reported increased current density through P-type voltage-gated Ca2+ channels in inferior colliculus (IC) neurons during alcohol withdrawal. However, the molecular correlate of this increased P-type channel current is currently unknown. Here, we probe changes in mRNA and protein expression of the pore-forming CaV2.1-α1 (P/Q-type) subunits in IC neurons during the course of alcohol withdrawal-induced seizures (AWSs). Rats received three daily doses of ethanol or the vehicle every 8 h for 4 consecutive days. The IC was dissected at various time intervals following alcohol withdrawal, and the mRNA and protein levels of the CaV2.1-α1 subunits were measured. In separate experiments, rats were tested for acoustically evoked seizure susceptibility 3, 24, and 48 h after alcohol withdrawal. AWSs were observed 24 h after withdrawal; no seizures were observed at 3 or 48 h or in the control-treated rats. Compared to control-treated rats, the mRNA levels of the CaV2.1-α1 subunit were increased 1.9-fold and 2.1-fold at 3 and 24 h, respectively; change in mRNA expression was nonsignificant at 48 h following alcohol withdrawal. Western blot analyses revealed that protein levels of the CaV2.1-α1 subunits were not altered in IC neurons following alcohol withdrawal. We conclude that expression of the Cacna1a mRNA increased before the onset of AWS susceptibility, suggesting that altered CaV2.1 channel expression may play a role in AWS pathogenesis.
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N'Gouemo P. Voltage-Sensitive Calcium Channels in the Brain: Relevance to Alcohol Intoxication and Withdrawal. Handb Exp Pharmacol 2018; 248:263-280. [PMID: 29500720 DOI: 10.1007/164_2018_93] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/25/2023]
Abstract
Voltage-sensitive Ca2+ (CaV) channels are the primary route of depolarization-induced Ca2+ entry in neurons and other excitable cells, leading to an increase in intracellular Ca2+ concentration ([Ca2+]i). The resulting increase in [Ca2+]i activates a wide range of Ca2+-dependent processes in neurons, including neurotransmitter release, gene transcription, activation of Ca2+-dependent enzymes, and activation of certain K+ channels and chloride channels. In addition to their key roles under physiological conditions, CaV channels are also an important target of alcohol, and alcohol-induced changes in Ca2+ signaling can disturb neuronal homeostasis, Ca2+-mediated gene transcription, and the function of neuronal circuits, leading to various neurological and/or neuropsychiatric symptoms and disorders, including alcohol withdrawal induced-seizures and alcoholism.
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Affiliation(s)
- Prosper N'Gouemo
- Department of Pediatrics, Georgetown University Medical Center, Washington, DC, USA.
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Akinfiresoye LR, Miranda C, Lovinger DM, N'Gouemo P. Alcohol Withdrawal Increases Protein Kinase A Activity in the Rat Inferior Colliculus. Alcohol Clin Exp Res 2016; 40:2359-2367. [PMID: 27716957 DOI: 10.1111/acer.13223] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/23/2016] [Accepted: 08/24/2016] [Indexed: 11/27/2022]
Abstract
BACKGROUND Cyclic AMP-dependent protein kinase A (PKA) signaling is a key target for the action of alcohol and may therefore play a role in the pathophysiology of alcohol withdrawal seizures (AWSs). Here, we investigated the role of PKA activity with respect to increased seizure susceptibility in rats that were subjected to alcohol withdrawal. METHODS Adult male Sprague Dawley rats received 3 daily doses of ethanol (EtOH) (or vehicle) for 4 consecutive days. Rats were then tested for susceptibility to acoustically evoked AWSs 3, 24, and 48 hours after the last alcohol dose. In separate experiments, the inferior colliculus (IC) was collected at these same time points from rats subjected to alcohol withdrawal and control rats following alcohol withdrawal. PKA activity, catalytic Cα (PKACα ) protein, regulatory RIIα (PKARIIα ) protein, and RIIβ (PKARIIβ ) protein were measured in the IC. Lastly, in situ pharmacological studies were performed to evaluate whether inhibiting PKA activity in the IC suppressed AWSs. RESULTS In the EtOH-treated group, AWSs were observed at the 24-hour time point, but not at the 3-hour or 48-hour time points. In the IC, PKA activity was significantly higher both 3 hours (i.e., before AWS susceptibility) and 24 hours after the last alcohol dose (when AWS susceptibility peaked) than in control rats. Consistent with these findings, protein levels of the PKACα subunit were significantly increased in the IC both 3 and 24 hours after the last alcohol dose. Lastly, in situ inhibition of PKA activity within the IC suppressed AWSs. CONCLUSIONS The increase in PKA activity and PKACα protein expression in the IC preceded the occurrence of AWSs, and inhibiting PKA activity within the IC suppressed acoustically evoked AWSs. Together, these findings suggest that altered PKA activity plays a key role in the pathogenesis of AWSs.
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Affiliation(s)
- Luli R Akinfiresoye
- Department of Pediatrics, Georgetown University Medical Center, Washington, District of Columbia
| | - Clive Miranda
- Department of Pediatrics, Georgetown University Medical Center, Washington, District of Columbia
| | - David M Lovinger
- Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, National Institutes of Health, Bethesda, Maryland
| | - Prosper N'Gouemo
- Department of Pediatrics, Georgetown University Medical Center, Washington, District of Columbia.
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N'Gouemo P, Akinfiresoye LR, Allard JS, Lovinger DM. Alcohol Withdrawal-Induced Seizure Susceptibility is Associated with an Upregulation of CaV1.3 Channels in the Rat Inferior Colliculus. Int J Neuropsychopharmacol 2015; 18:pyu123. [PMID: 25556199 PMCID: PMC4458366 DOI: 10.1093/ijnp/pyu123] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/30/2014] [Accepted: 12/30/2014] [Indexed: 11/16/2022] Open
Abstract
BACKGROUND We previously reported increased current density through L-type voltage-gated Ca(2+) (CaV1) channels in inferior colliculus (IC) neurons during alcohol withdrawal. However, the molecular correlate of this increased CaV1 current is currently unknown. METHODS Rats received three daily doses of ethanol every 8 hours for 4 consecutive days; control rats received vehicle. The IC was dissected at various time intervals following alcohol withdrawal, and the mRNA and protein levels of the CaV1.3 and CaV1.2 α1 subunits were measured. In separate experiments, rats were tested for their susceptibility to alcohol withdrawal-induced seizures (AWS) 3, 24, and 48 hours after alcohol withdrawal. RESULTS In the alcohol-treated group, AWS were observed 24 hours after withdrawal; no seizures were observed at 3 or 48 hours. No seizures were observed at any time in the control-treated rats. Compared to control-treated rats, the mRNA level of the CaV1.3 α1 subunit was increased 1.4-fold, 1.9-fold, and 1.3-fold at 3, 24, and 48 hours, respectively. In contrast, the mRNA level of the CaV1.2 α1 subunit increased 1.5-fold and 1.4-fold at 24 and 48 hours, respectively. At 24 hours, Western blot analyses revealed that the levels of the CaV1.3 and CaV1.2 α1 subunits increased by 52% and 32%, respectively, 24 hours after alcohol withdrawal. In contrast, the CaV1.2 and CaV1.3 α1 subunits were not altered at either 3 or 48 hours during alcohol withdrawal. CONCLUSIONS Expression of the CaV1.3 α1 subunit increased in parallel with AWS development, suggesting that altered L-type CaV1.3 channel expression is an important feature of AWS pathogenesis.
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Affiliation(s)
- Prosper N'Gouemo
- Georgetown University Medical Center, Department of Pediatrics, Washington DC (Drs N'Gouemo and Akinfiesoye); Howard University College of Medicine, Department of Physiology & Biophysics, Washington DC (Dr Allard); Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Rockville, MD (Dr Lovinger).
| | - Luli R Akinfiresoye
- Georgetown University Medical Center, Department of Pediatrics, Washington DC (Drs N'Gouemo and Akinfiesoye); Howard University College of Medicine, Department of Physiology & Biophysics, Washington DC (Dr Allard); Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Rockville, MD (Dr Lovinger)
| | - Joanne S Allard
- Georgetown University Medical Center, Department of Pediatrics, Washington DC (Drs N'Gouemo and Akinfiesoye); Howard University College of Medicine, Department of Physiology & Biophysics, Washington DC (Dr Allard); Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Rockville, MD (Dr Lovinger)
| | - David M Lovinger
- Georgetown University Medical Center, Department of Pediatrics, Washington DC (Drs N'Gouemo and Akinfiesoye); Howard University College of Medicine, Department of Physiology & Biophysics, Washington DC (Dr Allard); Laboratory for Integrative Neuroscience, National Institute on Alcohol Abuse and Alcoholism, Rockville, MD (Dr Lovinger)
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N’Gouemo P, Morad M. Alcohol withdrawal is associated with a downregulation of large-conductance Ca²⁺-activated K⁺ channels in rat inferior colliculus neurons. Psychopharmacology (Berl) 2014; 231:2009-18. [PMID: 24241791 PMCID: PMC3988246 DOI: 10.1007/s00213-013-3346-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 10/22/2013] [Indexed: 10/26/2022]
Abstract
RATIONALE Large conductance calcium-activated potassium (BK(Ca) or K(Ca)1.1) channels are well-known molecular targets for the action of alcohol and therefore may play an important role in the pathogenesis of alcohol withdrawal syndrome. OBJECTIVES We evaluate the modifications of total outward K⁺ currents and protein expression of BK(Ca) channels α-subunit in inferior colliculus (IC) neurons obtained from controls and rats subjected to alcohol withdrawal associated with enhanced susceptibility to seizures. METHODS Outward K⁺ currents and BK(Ca) channel proteins were measured using the whole cell configuration of patch clamp techniques and Western blot analysis, respectively. RESULTS Total outward K⁺ current density was significantly reduced in IC neurons at 24 and 48 h during the alcohol withdrawal period when the susceptibility to seizures was maximal and absent, respectively. The iberiotoxin-sensitive (BK(Ca)) current density and conductance also were significantly reduced at 24 h following alcohol withdrawal. Consistent with functional data, the levels of protein expression of α-subunit associated with BK(Ca) channels also was significantly reduced in IC neurons at 24 and 48 h following alcohol withdrawal. CONCLUSIONS The downregulation of BK(Ca) channels outlasts the finite period of elevated susceptibility to alcohol withdrawal seizures. These findings indicate that BK(Ca) channels, per se, may not be fundamentally important for the generation of alcohol withdrawal seizures.
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Affiliation(s)
- Prosper N’Gouemo
- Department of Pediatrics, Georgetown University Medical Center
,Address correspondence to: Department of Pediatrics, Georgetown University Medical Center, 3900 Reservoir Rd, NW, Washington, DC 20057, TEL: +1-202-687-8464; FAX: +202-444-7161,
| | - Martin Morad
- Department of Pharmacology, Georgetown University Medical Center
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N'Gouemo P, Yasuda R, Faingold CL. Seizure susceptibility is associated with altered protein expression of voltage-gated calcium channel subunits in inferior colliculus neurons of the genetically epilepsy-prone rat. Brain Res 2009; 1308:153-7. [PMID: 19836362 DOI: 10.1016/j.brainres.2009.10.019] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2009] [Revised: 10/02/2009] [Accepted: 10/08/2009] [Indexed: 10/20/2022]
Abstract
The inferior colliculus (IC) is the consensus site for seizure initiation in the genetically epilepsy-prone rat (GEPR). We have previously reported that the current density of high threshold voltage-activated (HVA) calcium (Ca(2+)) channels was markedly enhanced in IC neurons of the GEPR-3 (moderate seizure severity substrain of the GEPR). The present study examines whether subunit protein levels of HVA Ca(2+) channels are altered in IC neurons that exhibit enhanced Ca(2+) current density. Quantification shows that the levels of protein expression of the Ca(2+) channel pore-forming alpha1D (L-type) and alpha1E subunits (R-type) were significantly increased in IC neurons of seizure-naive GEPR-3s (SN-GEPR-3s) compared to control Sprague-Dawley (SD) rats. Significant increases and decreases in the levels of protein expression of Ca(2+) channel regulatory beta3 and alpha2delta subunits occurred in IC neurons of SN-GEPR-3s compared to control SD rats, respectively. No changes occurred in the protein expression of Ca(2+) channel pore-forming alpha1A (P/Q-type), alpha1B (N-type) and alpha1C (L-type) subunits in IC neurons of SN-GEPR-3s compared to control SD rats. A single seizure selectively enhanced protein expression of Ca(2+) channel alpha1A subunits in IC neurons of GEPR-3s. Thus, up-regulation of Ca(2+) channel alpha1D and alpha1E subunits may represent the molecular mechanisms for the enhanced current density of L- and R-type of HVA Ca(2+) channels in IC neurons of the GEPR, and may contribute to the genetic basis of their enhanced seizure susceptibility. The up-regulation of Ca(2+) channel alpha1A subunits induced by seizures may contribute to the increasing IC neuronal excitability that results from repetitive seizures in the GEPR.
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Affiliation(s)
- Prosper N'Gouemo
- Department of Pediatrics and Interdisciplinary Program in Neuroscience, Georgetown University Medical Center, Washington, DC 20057, USA.
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N'Gouemo P, Yasuda RP, Faingold CL. Protein expression of small conductance calcium-activated potassium channels is altered in inferior colliculus neurons of the genetically epilepsy-prone rat. Brain Res 2009; 1270:107-11. [PMID: 19254702 PMCID: PMC2697038 DOI: 10.1016/j.brainres.2009.02.034] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2008] [Revised: 02/06/2009] [Accepted: 02/13/2009] [Indexed: 11/28/2022]
Abstract
The genetically epilepsy-prone rat (GEPR) exhibits inherited predisposition to sound stimuli-induced generalized tonic-clonic seizures (audiogenic reflex seizures) and is a valid model to study the physiopathology of epilepsy. In this model, the inferior colliculus (IC) exhibits enhanced neuronal firing that is critical in the initiation of reflex audiogenic seizures. The mechanisms underlying IC neuronal hyperexcitability that leads to seizure susceptibility are not as yet fully understood. The present report shows that the levels of protein expression of SK1 and SK3 subtypes of the small conductance Ca2+-activated K+ channels were significantly decreased, while SK2 channel proteins were increased in IC neurons of seizure-naive GEPR-3s (SN-GEPR-3), as compared to control Sprague-Dawley rats. No significant change was found in the expression of BK channel proteins in IC neurons of SN-GEPR-3s. Single episode of reflex audiogenic seizures in the GEPR-3s did not significantly alter the protein expression of SK1-3 and BK channels in IC neurons compared to SN-GEPR-3s. Thus, downregulation of SK1 and SK3 channels and upregulation of SK2 channels provide direct evidence that these Ca2+-activated K+ channels play important roles in IC neuronal hyperexcitability that leads to inherited seizure susceptibility in the GEPR.
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Affiliation(s)
- Prosper N'Gouemo
- Department of Pediatrics, Bldg D, Room 285, Georgetown University Medical Center, 3900 Reservoir Rd, NW, Washington, DC 20057, USA.
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N'gouemo P, Faingold CL, Morad M. Calcium channel dysfunction in inferior colliculus neurons of the genetically epilepsy-prone rat. Neuropharmacology 2008; 56:665-75. [PMID: 19084544 DOI: 10.1016/j.neuropharm.2008.11.005] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/31/2008] [Revised: 11/25/2008] [Accepted: 11/26/2008] [Indexed: 11/29/2022]
Abstract
Voltage-gated calcium (Ca(2+)) channels are thought to play an important role in epileptogenesis and seizure generation. Here, using the whole cell configuration of patch-clamp techniques, we report on the modifications of biophysical and pharmacological properties of high threshold voltage-activated Ca(2+) channel currents in inferior colliculus (IC) neurons of the genetically epilepsy-prone rats (GEPR-3s). Ca(2+) channel currents were measured by depolarizing pulses from a holding potential of - 80 mV using barium (Ba(2+)) as the charge carrier. We found that the current density of high threshold voltage-activated Ca(2+) channels was significantly larger in IC neurons of seizure-naive GEPR-3s compared to control Sprague-Dawley rats, and that seizure episodes further enhanced the current density in the GEPR-3s. The increased current density was reflected by both a - 20 mV shifts in channel activation and a 25% increase in the non-inactivating fraction of channels in seizure-naive GEPR-3s. Such changes were reduced by seizure episodes in the GEPR-3s. Pharmacological analysis of the current density suggests that upregulation of L-, N- and R-type of Ca(2+) channels may contribute to IC neuronal hyperexcitability that leads to seizure susceptibility in the GEPR-3s.
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Affiliation(s)
- Prosper N'gouemo
- Department of Pediatrics, Georgetown University Medical Center, 3900 Reservoir Rd, NW, Washington, DC 20057, United States.
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