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Wang M, Gu Y, Li Q, Feng B, Lv X, Zhang H, Kong Q, Dong Z, Tian X, Zhang Y. The Traf2 and NcK interacting kinase inhibitor NCB-0846 suppresses seizure activity involving the decrease of GRIA1. Genes Dis 2024; 11:100997. [PMID: 38292191 PMCID: PMC10826163 DOI: 10.1016/j.gendis.2023.03.036] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2023] [Revised: 03/09/2023] [Accepted: 03/29/2023] [Indexed: 02/01/2024] Open
Abstract
Epilepsy, one of the most common neurological disorders, is characterized by spontaneous recurrent seizures. Temporal lobe epilepsy (TLE) is one of the most common medically intractable seizure disorders. Traf2-and NcK-interacting kinase (TNIK) has recently attracted attention as a critical modulation target of many neurological and psychiatric disorders, but its role in epilepsy remains unclear. In this study, we hypothesized the involvement of TNIK in epilepsy and investigated TNIK expression in patients with intractable TLE and in a pilocarpine-induced rat model of epilepsy by western blotting, immunofluorescence, and immunohistochemistry. A pentylenetetrazole (PTZ)-induced epilepsy rat model was used to determine the effect of the TNIK inhibitor NCB-0846 on behavioral manifestations of epilepsy. Coimmunoprecipitation (Co-IP)/mass spectrometry (MS) was used to identify the potential mechanism. Through Co-IP, we detected and confirmed the main potential TNIK interactors. Subcellular fractionation was used to establish the effect of NCB-0846 on the expression of the main interactors in postsynaptic density (PSD) fractions. We found that TNIK was primarily located in neurons and decreased significantly in epilepsy model rats and TLE patients compared with controls. NCB-0846 delayed kindling progression and decreased seizure severity. Co-IP/MS identified 63 candidate TNIK interactors in rat hippocampi, notably CaMKII. Co-IP showed that TNIK might correlate with endogenous GRIA1, SYN2, PSD-95, CaMKIV, GABRG1, and GABRG2. In addition, the significant decrease in GRIA1 in hippocampal total lysate and PSDs after NCB-0846 treatment might help modify the progression of PTZ kindling. Our results suggest that TNIK contributes to epileptic pathology and is a potential antiepileptic drug target.
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Affiliation(s)
- Min Wang
- Department of Neurology, Affiliated Hospital of Jining Medical University, Jining, Shandong 272000, China
| | - Yixue Gu
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Qiubo Li
- Department of Pediatrics, Affiliated Hospital of Jining Medical University, Jining, Shandong 272000, China
| | - Bangzhe Feng
- Department of Neurology, Affiliated Hospital of Jining Medical University, Jining, Shandong 272000, China
| | - Xinke Lv
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Hao Zhang
- Department of Neurosurgery, Affiliated Hospital of Jining Medical University, Jining, Shandong 272000, China
| | - Qingxia Kong
- Department of Neurology, Affiliated Hospital of Jining Medical University, Jining, Shandong 272000, China
| | - Zhifang Dong
- Pediatric Research Institute, Ministry of Education Key Laboratory of Child Development and Disorders, National Clinical Research Center for Child Health and Disorders, Chongqing Key Laboratory of Translational Medical Research in Cognitive Development and Learning and Memory Disorders, Children's Hospital of Chongqing Medical University, Chongqing 400014, China
| | - Xin Tian
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical University, Chongqing Key Laboratory of Neurology, Chongqing 400016, China
| | - Yanke Zhang
- Department of Neurology, Affiliated Hospital of Jining Medical University, Jining, Shandong 272000, China
- Center for Excellence in Brain Science and Intelligence Technology, Chinese Academy of Sciences, Shanghai 200031, China
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Proietti Onori M, van Woerden GM. Role of calcium/calmodulin-dependent kinase 2 in neurodevelopmental disorders. Brain Res Bull 2021; 171:209-220. [PMID: 33774142 DOI: 10.1016/j.brainresbull.2021.03.014] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/09/2020] [Revised: 03/17/2021] [Accepted: 03/18/2021] [Indexed: 01/28/2023]
Abstract
Neurodevelopmental disorders are a complex and heterogeneous group of neurological disorders characterized by their early-onset and estimated to affect more than 3% of children worldwide. The rapid advancement of sequencing technologies in the past years allowed the identification of hundreds of variants in several different genes causing neurodevelopmental disorders. Between those, new variants in the Calcium/calmodulin dependent protein kinase II (CAMK2) genes were recently linked to intellectual disability. Despite many years of research on CAMK2, this proves for the first time that this well-known and highly conserved molecule plays an important role in the human brain. In this review, we give an overview of the identified CAMK2 variants, and we speculate on potential mechanisms through which dysfunctions in CAMK2 result in neurodevelopmental disorders. Additionally, we discuss how the identification of CAMK2 variants might result in new exciting discoveries regarding the function of CAMK2 in the human brain.
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Affiliation(s)
- Martina Proietti Onori
- Department of Neuroscience, Erasmus MC, Rotterdam, 3015 GD, the Netherlands; The ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus MC, Rotterdam, 3015 GD, the Netherlands
| | - Geeske M van Woerden
- Department of Neuroscience, Erasmus MC, Rotterdam, 3015 GD, the Netherlands; The ENCORE Expertise Center for Neurodevelopmental Disorders, Erasmus MC, Rotterdam, 3015 GD, the Netherlands.
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Voltage-Dependent Calcium Channels, Calcium Binding Proteins, and Their Interaction in the Pathological Process of Epilepsy. Int J Mol Sci 2018; 19:ijms19092735. [PMID: 30213136 PMCID: PMC6164075 DOI: 10.3390/ijms19092735] [Citation(s) in RCA: 40] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2018] [Revised: 09/06/2018] [Accepted: 09/07/2018] [Indexed: 01/08/2023] Open
Abstract
As an important second messenger, the calcium ion (Ca2+) plays a vital role in normal brain function and in the pathophysiological process of different neurodegenerative diseases including Alzheimer’s disease (AD), Parkinson’s disease (PD), and epilepsy. Ca2+ takes part in the regulation of neuronal excitability, and the imbalance of intracellular Ca2+ is a trigger factor for the occurrence of epilepsy. Several anti-epileptic drugs target voltage-dependent calcium channels (VDCCs). Intracellular Ca2+ levels are mainly controlled by VDCCs located in the plasma membrane, the calcium-binding proteins (CBPs) inside the cytoplasm, calcium channels located on the intracellular calcium store (particular the endoplasmic reticulum/sarcoplasmic reticulum), and the Ca2+-pumps located in the plasma membrane and intracellular calcium store. So far, while many studies have established the relationship between calcium control factors and epilepsy, the mechanism of various Ca2+ regulatory factors in epileptogenesis is still unknown. In this paper, we reviewed the function, distribution, and alteration of VDCCs and CBPs in the central nervous system in the pathological process of epilepsy. The interaction of VDCCs with CBPs in the pathological process of epilepsy was also summarized. We hope this review can provide some clues for better understanding the mechanism of epileptogenesis, and for the development of new anti-epileptic drugs targeting on VDCCs and CBPs.
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Mody I, Soltesz I. Activity‐dependent changes in structure and function of hippocampal neurons. Hippocampus 2013. [DOI: 10.1002/hipo.1993.4500030713] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Affiliation(s)
- Istvan Mody
- Department of Neurology and Neurological Sciences, Stanford University Medical Center, Stanford, California, U.S.A
| | - Ivan Soltesz
- Department of Neurology and Neurological Sciences, Stanford University Medical Center, Stanford, California, U.S.A
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Liu XB, Murray KD. Neuronal excitability and calcium/calmodulin-dependent protein kinase type II: location, location, location. Epilepsia 2012; 53 Suppl 1:45-52. [PMID: 22612808 DOI: 10.1111/j.1528-1167.2012.03474.x] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Calcium/calmodulin-dependent protein kinase type II (CaMKII) is a highly abundant serine/threonine kinase comprising a significant fraction of total protein in mammalian forebrain and forming a major component of the postsynaptic density. CaMKII is essential for certain forms of synaptic plasticity and memory consolidation and this is mediated through substrate binding and intramolecular phosphorylation of holoenzyme subunits. CaMKII is multifunctional; it targets a variety of cellular substrates, and this diversity depends on holoenzyme subunit composition. CaMKII comprises homooligomeric and heterooligomeric complexes generated from four subunits (α, β, δ, and γ) encoded by separate genes that are further expanded by extensive alternative splicing to more than 30 different isoforms. Much attention has been paid to understanding the regulation of CaMKII function through its structural diversity and/or substrate specificity. However, given the importance of subunit composition to holoenzyme activity, it is likely that specificity of cellular expression of CaMKII isoforms also plays a major role in regulation of enzyme function. Herein we review the cellular colocalization of CaMKII isoforms with special regard to the cell-type specificity of isoform expression in brain. In addition, we highlight the remarkable specificity of subcellular localization by the CaMKIIα isoform. In addition, we discuss the role that this cellular specificity of expression might play in propagating the type of recurrent neuronal activity associated with disorders such as temporal lobe epilepsy.
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Affiliation(s)
- Xiao-Bo Liu
- Center for Neuroscience, University of California-Davis, Davis, CA 95618, U.S.A
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Thomas RH, Foley KA, Mepham JR, Tichenoff LJ, Possmayer F, MacFabe DF. Altered brain phospholipid and acylcarnitine profiles in propionic acid infused rodents: further development of a potential model of autism spectrum disorders. J Neurochem 2010; 113:515-29. [PMID: 20405543 DOI: 10.1111/j.1471-4159.2010.06614.x] [Citation(s) in RCA: 88] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
Recent studies have demonstrated intraventricular infusions of propionic acid (PPA) a dietary and enteric short-chain fatty acid can produce brain and behavioral changes similar to those observed in autism spectrum disorder (ASD). The effects of PPA were further evaluated to determine if there are any alterations in brain lipids associated with the ASD-like behavioral changes observed following intermittent intraventricular infusions of PPA, the related enteric metabolite butyric acid (BUT) or phosphate-buffered saline vehicle. Both PPA and BUT produced significant increases (p < 0.001) in locomotor activity (total distance travelled and stereotypy). PPA and to a lesser extent BUT infusions decreased the levels of total monounsaturates, total omega6 fatty acids, total phosphatidylethanolamine plasmalogens, the ratio of omega6 : omega3 and elevated the levels of total saturates in separated phospholipid species. In addition, total acylcarnitines, total longchain (C12-C24) acylcarnitines, total short-chain (C2 to C9) acylcarnitines, and the ratio of bound to free carnitine were increased following infusions with PPA and BUT. These results provide evidence of a relationship between changes in brain lipid profiles and the occurrence of ASD-like behaviors using the autism rodent model. We propose that altered brain fatty acid metabolism may contribute to ASD.
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Affiliation(s)
- Raymond H Thomas
- The Kilee Patchell-Evans Autism Research Group, Department of Psychology and Biology, University of Western Ontario, London, Ontario, Canada
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Folkerts MM, Parks EA, Dedman JR, Kaetzel MA, Lyeth BG, Berman RF. Phosphorylation of Calcium Calmodulin—Dependent Protein Kinase II following Lateral Fluid Percussion Brain Injury in Rats. J Neurotrauma 2007; 24:638-50. [PMID: 17439347 DOI: 10.1089/neu.2006.0188] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Traumatic brain injury (TBI) can dramatically increase levels of intracellular calcium ([Ca(2+)](i)). One consequence of increased [Ca(2+)](i) would be altered activity and function of calcium-regulated proteins, including calcium-calmodulin-dependent protein kinase II (CaMKII), which is autophosphorylated on Thr(286)(pCaMKII(286)) in the presence of calcium and calmodulin. Therefore, we hypothesized that TBI would result in increased levels of pCaMKII(286), and that such increases would occur early after injury in brain regions known to be damaged following lateral fluid percussion TBI (i.e., hippocampus and cortex). In order to test this hypothesis, immunostaining of CaMKII was examined in rat hippocampus and cortex after lateral fluid percussion (LFP) injury using an antibody directed against pCaMKII(286). LFP injury produced a marked increase in pCaMKII(286) immunostaining in the hippocampus and overlying cortex 30 min after TBI. The pattern of increased immunostaining was uneven, and unexpectedly absent in some hippocampal CA3 pyramidal neurons. This suggests that phosphatase activity may also increase following TBI, resulting in dephosphorylation of pCaMKII(286) in subpopulations of CA3 pyramidal neurons. Western blotting confirmed a rapid increase in levels of pCaMKII(286) at 10 and 30 min after brain injury, and that it was transient and no longer significantly elevated when examined at 3, 8, and 24 h. These results demonstrate that TBI alters the autophosphorylation state of CaMKII, an important neuronal regulator of critical cell functions, including enzyme activities, cell structure, gene expression, and neuronal plasticity, and provide a molecular mechanism that is likely to contribute to cell injury and impaired plasticity after TBI.
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Affiliation(s)
- Michael M Folkerts
- Department of Neurological Surgery, University of California Davis, Davis, California 95616, USA
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8
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Dong Y, Rosenberg HC. Brief seizure activity alters Ca2+/calmodulin dependent protein kinase II dephosphorylation and subcellular distribution in rat brain for several hours. Neurosci Lett 2004; 357:95-8. [PMID: 15036583 DOI: 10.1016/j.neulet.2003.11.069] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2003] [Revised: 11/14/2003] [Accepted: 11/21/2003] [Indexed: 11/20/2022]
Abstract
The effect of a brief pentylenetetrazol (PTZ) convulsive seizure on rat cerebral cortical Ca2+/calmodulin dependent protein kinase II (CaMKII) was investigated. By immunoblot, it was found that a single PTZ seizure, lasting less than a minute, caused translocation of CaMKII alpha-subunit (alpha-CaMKII) from the particulate to the soluble fraction for several hours, paralleled by a dramatic loss of alpha-CaMKII Thr286 phosphorylation. The reduced alpha-CaMKII Thr286 phosphorylation apparently resulted from enhanced phosphatase activity following PTZ seizure, especially in the particulate fraction. CaMKII translocation and phosphatase activation following a brief seizure episode can both contribute to long-lasting CaMKII regulation far outlasting the immediate effects of the seizure on neuronal function.
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Affiliation(s)
- Yu Dong
- Department of Pharmacology and Therapeutics, Medical College of Ohio, 3035 Arlington Avenue, Toledo, OH 43614-5804, USA
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9
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Dong Y, Rosenberg HC. Prolonged changes in Ca2+/calmodulin-dependent protein kinase II after a brief pentylenetetrazol seizure; potential role in kindling. Epilepsy Res 2004; 58:107-17. [PMID: 15120742 DOI: 10.1016/j.eplepsyres.2004.01.003] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2003] [Revised: 01/08/2004] [Accepted: 01/14/2004] [Indexed: 10/26/2022]
Abstract
This study evaluated the alteration of CaMKII autophosphorylation and distribution in rat brain following a single, brief pentylenetetrazol (PTZ) seizure and during PTZ kindling. Total CaMKII alpha subunit (alpha-CaMKII) and alpha-CaMKII phosphorylated at Thr(286) were detected by immunoblot. A large decrease in CaMKII Thr(286) phosphorylation, as well as CaMKII translocation from particulate to soluble fraction was observed in both cerebral cortex and hippocampus 0.5-4 h after the brief PTZ convulsion. These changes reverted to control values by 12 h. These long-lasting changes in CaMKII autophosphorylation and subcellular distribution after a brief seizure suggested that CaMKII could be involved in carrying forward the signal resulting from brief seizure activity, at least for a few hours, as would be required for kindling to occur. In PTZ kindled rats, convulsions produced changes in CaMKII Thr(286) phosphorylation and distribution in the same direction and of similar magnitude as after the acute convulsion, but lasting for a much longer time. In fact, reduced Thr(286) phosphorylation of alpha-CaMKII was observed up to 48 h, completely bridging the interval between PTZ injections. Similar, but intermediate changes were found in tissue from rats that were only partially kindled. These results implicate CaMKII as a molecular messenger in the acquisition of PTZ kindling.
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Affiliation(s)
- Yu Dong
- Department of Pharmacology and Therapeutics, Medical College of Ohio, 3035 Arlington Avenue, Toledo, OH 43614-5804, USA
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10
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Kikuchi S, Iwasa H, Sato T. Lasting changes in NMDAR1 mRNA level in various regions of cerebral cortex in epileptogenesis of amygdaloid-kindled rat. Psychiatry Clin Neurosci 2000; 54:573-7. [PMID: 11043808 DOI: 10.1046/j.1440-1819.2000.00755.x] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
The involvement of NMDA receptor subunit, NR1, with kindling phenomenon has been reported, but the role of NR1 in epileptogenesis is still unknown. We have examined the expression levels of NR1 mRNA in the cerebral cortices of amygdaloid-kindled rats. Northern blot analysis showed a significant increase in NR1 mRNA expression level in the ipsilateral frontal and temporal cortices at 4 weeks after the last generalized seizure. At the same time, NR1 mRNA decreased in the bilateral piriform cortices. These data suggest that NR1-mediated transmission may have an impact in the neurobiological basis of enduring epileptogenesis.
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Affiliation(s)
- S Kikuchi
- Division of Drug Dependence and Psychotropic Drug Clinical Research, National Institute of Mental Health, National Center of Neurology and Psychiatry, Ichikawa, Japan.
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Atack JR, Cook SM, Hutson PH, File SE. Kindling induced by pentylenetetrazole in rats is not directly associated with changes in the expression of NMDA or benzodiazepine receptors. Pharmacol Biochem Behav 2000; 65:743-50. [PMID: 10764932 DOI: 10.1016/s0091-3057(99)00267-1] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 10/17/2022]
Abstract
Repeated injections of a subconvulsant dose of pentylenetetrazole (PTZ, 30 mg/kg IP three times weekly for 13 injections) in Wistar and hooded Lister rats resulted in kindled seizures, the extent of which varied between strains. Wistar rats achieved stage 4 of clonic-tonic seizures, whereas hooded Lister rats only reached stage 2 of convulsive waves axially through the body. Rats were killed 10 days after their final injection, and radioligand binding was used to measure the expression of NMDA receptors in cortex and hippocampus using [3H]MK-801 and [3H]L-689,560, the latter binding specifically to the NR1 subunit. [3H]Ro 15-1788 measured expression of GABA(A)-benzodiazepine binding sites containing alpha1, alpha2, alpha3, or alpha5 subunits. Specific analysis of GABA(A) receptors containing the alpha5 subunit, which are preferentially localized in the hippocampus, was assessed with [3H]L-655,708. In the cortex, there was no effect of strain or treatment on the K(D) or B(max) of any of the ligands. Similarly, there was no effect of strain or treatment on hippocampal [3H]L-689,560 or [3H]Ro 15-1788 binding. However, in the hippocampus there was a significant, albeit modest, effect of treatment on the B(max) of [3H]MK-801 binding and the B(max) and K(D) of [3H]L-655,708 binding, i.e., PTZ-treated rats had fewer [3H]MK-801 and [3H]L-655,708 binding sites (NMDA and alpha5-containing GABA(A) receptors, respectively), but, these reductions were significant only in the relatively seizure-insensitive hooded Lister strain. This suggests that the increased susceptibility to kindling in Wistar rats is not directly related to alterations in the expression of NMDA or GABA(A) receptors.
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Affiliation(s)
- J R Atack
- Merck Sharp & Dohme Research Laboratories, Neuroscience Research Centre, Terlings Park, Eastwick Road, Harlow, Essex, UK
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12
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Elisabetsky E, Brum LF, Souza DO. Anticonvulsant properties of linalool in glutamate-related seizure models. PHYTOMEDICINE : INTERNATIONAL JOURNAL OF PHYTOTHERAPY AND PHYTOPHARMACOLOGY 1999; 6:107-113. [PMID: 10374249 DOI: 10.1016/s0944-7113(99)80044-0] [Citation(s) in RCA: 127] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
Abstract
In order to investigate the pharmacodynamic basis of the previously-established anticonvulsant properties of linalool, we examined the effects of this compound on behavioral and neurochemical aspects of glutamate expression in experimental seizure models. Specifically, linalool effects were investigated to determine its inhibition of (i) L-[3H]glutamate binding at CNS (central nervous system membranes), (ii) N-methyl-D-aspartate (NMDA)-induced convulsions, (iii) quinolinic acid (QUIN)-induced convulsions, and the behavioral and neurochemical correlates of PTZ-kindling. The data indicate that linalool modulates glutamate activation expression in vitro (competitive antagonism of L-[3H]glutamate binding) and in vivo (delayed NMDA convulsions and blockage of QUIN convulsions). Linalool partially inhibited and significantly delayed the behavioral expression of PTZ-kindling, but did not modify the PTZ-kindling-induced increase in L-[3H]glutamate binding.
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Affiliation(s)
- E Elisabetsky
- Departamento de Farmacologia, Universidade Federal do Rio Grande do Sul, Porto Alegre, Brazil.
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Schröeder H, Becker A, Schröeder U, Hoellt V. 3H-L-glutamate binding and 3H-D-aspartate release from hippocampal tissue during the development of pentylenetetrazole kindling in rats. Pharmacol Biochem Behav 1999; 62:349-52. [PMID: 9972703 DOI: 10.1016/s0091-3057(98)00170-1] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
Abstract
Previous studies have proposed that there is an increase in the density of glutamate binding sites after pentylenetetrazol (PTZ) kindling, whereas the glutamate release is not altered. Little is known about the time course of these changes. Therefore, we studied 3H-L-glutamate binding to hippocampal membranes and K+-stimulated 3H-D-aspartate release from hippocampal slices of rats given PTZ 3, 7, and 13 times up to a fully kindling state. After three PTZ injections, amino acid release from hippocampal tissue slices was significantly enhanced in comparison to controls, whereas 3H-L-glutamate binding was not altered. After seven injections of PTZ, specific glutamate binding to hippocampal membranes tended to increase, and K+-stimulated 3H-D-aspartate release from rat hippocampal slices was normalized. The kindled state characterized by generalized clonic-tonic seizures was reached after 13 PTZ injections, and it was accompanied by an enhancement in the density of glutamate binding sites, whereas the chemically evoked amino acid release remained unchanged. It can be concluded that the amino acid release is increased in the early phase of PTZ kindling development, whereas after completion of kindling, the density of excitatory amino acid binding sites is enhanced.
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Affiliation(s)
- H Schröeder
- Institute of Pharmacology and Toxicology, Medical Faculty, Otto-von-Guericke University, Magdeburg, Germany
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14
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Schroeder H, Becker A, Grecksch G, Schroeder U, Hoellt V. The effect of pentylenetetrazol kindling on synaptic mechanisms of interacting glutamatergic and opioid system in the hippocampus of rats. Brain Res 1998; 811:40-6. [PMID: 9804884 DOI: 10.1016/s0006-8993(98)00929-9] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Endogenous opioids modulate processes of central excitability such as long-term potentiation and electrical kindling. Little is known about the neurochemical alterations in the interaction of the glutamatergic and opioid system in the development of pentylenetetrazol (PTZ) kindling in rats. Therefore, in the present study we investigated glutamate, DAMGO and naltrindole receptor binding, receptor protein expression by Western blot and ex vivo glutamate transmitter release in PTZ kindled rats. The specific 3H-DAMGO and -naltrindole binding to hippocampal membranes displayed no significant changes in kindled rats compared to controls. In contrast, the 3H-l-glutamate binding was significantly enhanced after completion of PTZ kindling. The expression of receptor protein for glutamate as well as the naloxone- and naltrindole-induced 3H-d-aspartate release from hippocampal slices did not alter in any case as a consequence of PTZ kindling. The PTZ induced enhancement of the glutamate binding sites in the hippocampus was downregulated to control level by natrindole treatment of rats prior to each PTZ application. Furthermore, naltrindole pretreatment of rats significantly inhibited the development of seizure susceptibility. In contrast, naloxone was not able to alter the seizure activity induced by PTZ as well as the transmitter receptor binding. The results are discussed in the light of a modulating role of delta-opioid receptors in PTZ kindling.
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Affiliation(s)
- H Schroeder
- Institute of Pharmacology and Toxicology, Medical Faculty, Otto-von-Guericke-University, D-39120-, Magdeburg, Leipziger Str. 44, Germany
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15
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Asai M, Benítez-King G. Variations of rat brain calmodulin content in dark and light phases: effect of pentylenetetrazol-induced kindling. Neurochem Res 1998; 23:1147-51. [PMID: 9712183 DOI: 10.1023/a:1020717732261] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Calmodulin (CaM) through activation of CaM-kinase II may be involved in the molecular mechanisms underlying the epileptogenic processes. Some evidence suggests that kindling responses change across the day-night cycle. In order to test if kindling stimulation modifies CaM content, we measured CaM concentrations in amygdala, hippocampus and hypothalamus obtained from control and kindled rats during light and darkness. Male Wistar rats (250-300 g), were injected i.p. with Pentylenetetrazol (PTZ) (35 mg/kg/24 h). Once chemical kindling was established, rats were sacrificed by decapitation at 10:30 a.m. and 01:30 a.m. The brains were obtained, and the amygdala, hippocampus and hypothalamus dissected. CaM content was measured in the cytosol and membrane fractions by radioimmunoassay. We found a significant increase in CaM content in cytosol and membrane fractions of both control and kindled rats during the dark phase. No significant differences in CaM concentrations were observed between control and experimental rats, whether during the light or the dark phase. The data suggest a well defined photoperiodic variation in CaM concentrations in limbic structures, despite the neuronal excitability produced by kindling. In addition, the observed CaM increases during the dark time may be related to a protective mechanism against enhanced sensitivity to seizures observed during the night.
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Affiliation(s)
- M Asai
- Laboratorio de Análisis Químicos, Instituto Mexicano de Psiquiatría, México DF México
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16
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Folbergrová J, Lisý V, Haugvicová R, Stastný F. Specific [3H]glutamate binding in the cerebral cortex and hippocampus of rats during development: effect of homocysteine-induced seizures. Neurochem Res 1997; 22:637-46. [PMID: 9131644 DOI: 10.1023/a:1022434406400] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
Specific [3H]glutamate binding to synaptic membranes from the cerebral cortex and hippocampus of 7-, 12- and 18-day-old rats was examined, both in control animals and during seizures induced by homocysteine. In the cerebral cortex a transient peak of glutamate binding was observed in 7-day-old group, whereas in the hippocampus it occurred in 12-day-old animals. Total specific [3H]glutamate binding was not influenced by preceding seizure activity in either of the age groups and both the studied regions. NMDA- and QA-sensitive glutamate bindings represent the highest portion of the total binding. Moreover, NMDA-sensitive binding in the cerebral cortex of 7-day-old rats is significantly higher as compared to the two more mature groups. The proportion of individual receptor subtypes on total binding in each age group was not influenced by preceding seizure activity. However, NMDA-sensitive binding in the hippocampus of 12-day-old rats, sacrificed during homocysteine-induced seizures, was significantly increased as compared to corresponding controls. In contrast to the effect of NMDA, AMPA, kainate and quisqualate which displaced to a different extent [3H]glutamate binding, homocysteine had no effect when added to membrane preparations. Similarly, [3H]CPP and [3H]AMPA bindings were not affected in the presence of homocysteine. It thus seems unlikely that homocysteine is an effective agonist for conventional ionotropic glutamate receptors. Its potential activity at some of the modulatory sites at the NMDA receptor channel complex or at metabotropic receptors has to be clarified in further experiments.
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Affiliation(s)
- J Folbergrová
- Institute of Physiology, Academy of Sciences of the Czech Republic, Prague, Czech Republic
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17
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Croucher MJ, Ruffle KL, Bradford HF. The effects of focal N-methyl-D-aspartate pretreatment on the parameters of amygdaloid electrical kindling. Eur J Pharmacol 1997; 319:207-13. [PMID: 9042592 DOI: 10.1016/s0014-2999(96)00868-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Evidence is accumulating for a role of glutamate in both the development (epileptogenesis) and spread of epileptic neuronal hyperactivity in the brain. In the present investigation we examined the influence of daily focal pretreatment with the selective glutamate receptor agonist N-methyl-D-aspartate (NMDA) on the parameters of amygdaloid electrical kindling, an animal model of human complex partial and secondary generalised focal seizures. Pretreatment with NMDA significantly increased the electrical afterdischarge threshold in this model. With subsequent daily suprathreshold electrical stimulation, however, NMDA pretreatment enhanced the kindling process as shown by both electroencephalographic and motor seizure responses. Marked reductions in the number of stimulations required to reach each distinct stage of kindling development were evident. The number of stimulations required to achieve the fully kindled state was approximately halved by pretreatment with NMDA (6.8 +/- 1.6 stimulations) compared with control, buffer-pretreated animals (11.6 +/- 1.4 stimulations; mean +/- S.E.M.; P < 0.05). Consistent with this, the mean durations of the electrically-evoked afterdischarges on most NMDA pretreatment days were significantly increased compared to those recorded in control animals. Importantly, fully kindled animals showed a markedly enhanced sensitivity to focally applied NMDA. The results of the present experiments provide strong in vivo evidence to support the concept that ion fluxes through NMDA receptor-linked cation channels play a major role in the mechanisms of kindling epileptogenesis. Extracellular glutamate at abnormally raised levels, acting at least in part via NMDA receptors, may be the principal agent triggering many forms of epilepsy.
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Affiliation(s)
- M J Croucher
- Department of Pharmacology, Charing Cross and Westminster Medical School, London, UK
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18
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Morimoto K, Sato K, Kashihara K, Hayabara T. Increased levels of mRNA for beta- but not alpha-subunit of calmodulin kinase II following kindled seizures. Brain Res Bull 1997; 43:375-80. [PMID: 9241440 DOI: 10.1016/s0361-9230(97)00022-1] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023]
Abstract
We studied levels of mRNA for the alpha- and beta-subunits of calmodulin (CaM) kinase II using the amygdaloid kindling model of epilepsy. There were significant increases in mRNA for the beta-subunit of CaM kinase II in the hippocampus 4-24 h after stage 5-kindled seizures. Moreover, this mRNA was significantly increased by 20.0-26.5% in the bilateral dentate gyrus 8 to 24 h after kindled seizures. The beta-subunit mRNA was also significantly increased by 13.5-19.0% in the CA3 on the side ipsilateral to the stimulation, 4 to 8 h after kindled seizures. mRNA for the alpha-subunit of CaM kinase II was not significantly changed in the regions examined for up to 24 h after the kindled seizures. These results suggest that CaM kinase II mediates the molecular processes that follow kindled seizures. It is possible that increases in CaM kinase II-dependent protein phosphorylation are associated with the plastic changes in kindling.
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Affiliation(s)
- K Morimoto
- Department of Neuropsychiatry, Faculty of Medicine, Kagawa Medical University, Japan
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19
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Vezzani A, Speciale C, Della Vedova F, Tamburin M, Benatti L. Alternative splicing at the C-terminal but not at the N-terminal domain of the NMDA receptor NR1 is altered in the kindled hippocampus. Eur J Neurosci 1995; 7:2513-7. [PMID: 8845957 DOI: 10.1111/j.1460-9568.1995.tb01050.x] [Citation(s) in RCA: 29] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/02/2023]
Abstract
Several lines of evidence suggest that N-methyl-D-aspartate (NMDA) receptors significantly contribute to the development of kindling. In addition, a lasting enhancement of the NMDA receptor function has been suggested to play a significant role in the chronic hyperexcitability occurring in the hippocampus after kindling epileptogenesis. We have investigated whether hippocampal kindling induces changes in the NMDA receptor at the molecular level by assessing the expression of mRNAs of the different spliced variants at the N-terminal (exon 5) and C-terminal (exon 21) position of the NMDA receptor 1 (NR1) gene by means of the reverse transcription-polymerase chain reaction. Alternative splicing at exon 5 confers different sensitivity of the NMDA receptor to polyamines while exon 21 encodes a 37-amino acid insert containing the major phosphorylation sites for protein kinase C. One week after the acquisition of stage 5 of kindling in rats (generalized tonic-clonic seizures), the relative abundance of the two alternatively spliced forms at the C-terminal domain, respectively containing (+) or lacking (-) exon 21, was reversed compared to controls (implanted with electrodes but not stimulated) in the dorsal hippocampus ipsilateral and contralateral to the electrical stimulation. The exon 21+/exon 21- mRNA ratio for controls was 1.3 +/- 0.04 (mean +/- SE); for ipsilaterally kindled rats it was 0.64 +/- 0.05 (P < 0.05), and for contralaterally kindled rats it was 0.48 +/- 0.07 (P < 0.01). Similar bilateral effects were observed in the ventral hippocampus (temporal pole). No changes were found 4 weeks after stage 5 seizures and 1 week after the induction of a single afterdischarge. No significant alterations were induced by kindling in the relative abundance of the spliced variants containing or lacking exon 5. Our findings show selective changes in alternative splicing of the NR1 gene after repeated application of an epileptogenic stimulus. This may generate receptors with different functional properties, which may contribute to the increased sensitivity for the induction of generalized seizures during kindling.
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Affiliation(s)
- A Vezzani
- Istituto di Ricerche Farmacologiche Mario Negri, Milano, Italy
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Karpova IV, Gorodinskii AI, Suvorov NF, Dambinova SA. Receptor binding of glutamate in the striatum of rats differing in learning capacity. NEUROSCIENCE AND BEHAVIORAL PHYSIOLOGY 1995; 25:98-103. [PMID: 7630506 DOI: 10.1007/bf02358575] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/26/2023]
Abstract
A comparative investigation has been carried out for the first time of the receptor binding of glutamate with synaptic membranes and coarse fractions of the postsynaptic enlargements isolated from the striatum of rats differing in their capacity to develop an alimentary instrumental reflex. It was demonstrated that the number of that glutamate binding sites on the postsynaptic enlargements isolated from the striatum of rats capable of rapidly developing an alimentary instrumental reflex was increased as compared with animals not subjected to training. This relationship is maintained two months after the termination of training.
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Affiliation(s)
- I V Karpova
- Laboratory of Physiology of Higher Nervous Activity, I. P. Pavlov Institute of Physiology, Russian Academy of Sciences, Saint Petersburg
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21
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Abstract
Kindling is an experimental model of epilepsy that involves activity-dependent changes in neuronal structure and function. During kindling, pathological changes may occur at several organizational levels of the nervous system, from alterations in gene-expression in individual neurons to the loss of specific neuronal populations and rearrangement of synaptic connectivity resulting from sustained stimulation of major excitatory pathways. This review summarizes recent developments in alterations at single neuronal and molecular levels that may be responsible for kindling epileptogenesis.
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Affiliation(s)
- I Mody
- Department of Anesthesiology/Pain Management, University of Texas Southwestern Medical Center, Dallas 75235-9068
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Schröder H, Becker A, Lössner B. Glutamate binding to brain membranes is increased in pentylenetetrazole-kindled rats. J Neurochem 1993; 60:1007-11. [PMID: 8094739 DOI: 10.1111/j.1471-4159.1993.tb03248.x] [Citation(s) in RCA: 103] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
The specific binding of L-[3H]glutamate to its receptors was investigated on crude membrane preparations from different brain regions of pentylenetetrazole-kindled rats using a binding assay technique. Pentylenetetrazole kindling induced by 10 intraperitoneal applications of 45 mg/kg over a period of 20 days resulted in a significant increase of both the convulsive susceptibility of animals to the convulsant and the specific L-[3H]glutamate binding in hippocampus and in motor, frontal, and inferotemporal (acoustic) cortex tested with a L-[3H]glutamate concentration of 50 nM. No differences were observed in the other brain structures studied. Kinetic studies indicated that the enhanced L-[3H]glutamate binding to hippocampal membranes from kindled rats reflects changes in the density of the glutamate binding sites rather than an increase in receptor affinity. To study the effect of acute generalized convulsions on L-[3H]glutamate binding to synaptosomal membranes of hippocampus and visual cortex, rats were treated 24 h before the experiment with 60 mg/kg of pentylenetetrazole, i.p. Under these conditions, no differences between treated and control rats were observed. From these findings, it is concluded that the increase in glutamate receptor density demonstrated in hippocampus and several neocortical brain structures of pentylenetetrazole-kindled rats may be the expression of a specific enhancement of susceptibility of glutamatergic systems to this excitatory amino acid developing in the course of formation of pentylenetetrazole-induced kindling.
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Affiliation(s)
- H Schröder
- Institute of Pharmacology and Toxicology, Medical Academy, Magdeburg, F.R.G
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Rostas JA, Dunkley PR. Multiple forms and distribution of calcium/calmodulin-stimulated protein kinase II in brain. J Neurochem 1992; 59:1191-202. [PMID: 1328514 DOI: 10.1111/j.1471-4159.1992.tb08428.x] [Citation(s) in RCA: 49] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022]
Affiliation(s)
- J A Rostas
- Neuroscience Group, Faculty of Medicine, University of Newcastle, New South Wales, Australia
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24
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Suzuki T, Okumura-Noji K, Ogura A, Kudo Y, Tanaka R. Antibody specific for the Thr-286-autophosphorylated alpha subunit of Ca2+/calmodulin-dependent protein kinase II. Proc Natl Acad Sci U S A 1992; 89:109-13. [PMID: 1309602 PMCID: PMC48185 DOI: 10.1073/pnas.89.1.109] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/26/2022] Open
Abstract
We report the production of an antibody specific for Ca2+/calmodulin-dependent protein kinase II (CaM-KII) autophosphorylated only at Thr-286 of the alpha subunit. Peptide Y-66 [sequence MHRQETVDC (Met-281 to Cys-289 of alpha subunit of CaM-KII)] was synthesized and phosphorylated by the CaM-KII endogenous to synaptic cytoskeleton (postsynaptic density-enriched fraction); the phosphorylated amino acid residue threonine corresponds to Thr-286 in the kinase alpha subunit. The phosphorylated Y-66 peptide was separated from the unphosphorylated peptide by HPLC and used as an immunogen after being coupled to hemocyanin. The antibodies that reacted with hemocyanin and unphosphorylated Y-66 peptide were adsorbed, and then IgG was purified. ELISA proved that the IgG obtained reacted specifically with phosphorylated Y-66 peptide. Immunoblot analysis showed that the antibody reacted specifically to the autophosphorylated CaM-KII both in purified and synaptic cytoskeleton-associated form. Appearance of CaM-KII subunits immunoreactive to anti-phosphorylated Y-66 antibody paralleled the generation of Ca(2+)-independent kinase activity. Immunocytochemical experiments clearly showed expression of the Thr-286- or Thr-287-autophosphorylated form of CaM-KII in cultured hippocampal cells treated with N-methyl-D-aspartate. Thus, this antibody could be extremely useful for studying the biological functions of CaM-KII.
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Affiliation(s)
- T Suzuki
- Department of Biochemistry, Nagoya City University Medical School, Japan
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25
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Siekevitz P. Possible role for calmodulin and the Ca2+/calmodulin-dependent protein kinase II in postsynaptic neurotransmission. Proc Natl Acad Sci U S A 1991; 88:5374-8. [PMID: 1647030 PMCID: PMC51875 DOI: 10.1073/pnas.88.12.5374] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022] Open
Abstract
The theory presented here is based on results from in vitro experiments and deals with three proteins in the postsynaptic density/membrane-namely, calmodulin, the Ca2+/calmodulin-dependent protein kinase, and the voltage-dependent Ca2+ channel. It is visualized that, in vivo in the polarized state of the membrane, calmodulin is bound to the kinase; upon depolarization of the membrane and the intrusion of Ca2+, Ca2(+)-bound calmodulin activates the autophosphorylation of the kinase. Calmodulin is visualized as having less affinity for the phosphorylated form of the kinase and is translocated to the voltage-dependent Ca2+ channel. There, with its bound Ca2+, it acts as a Ca2+ sensor, to close off the Ca2+ channel of the depolarized membrane. At the same time, it is thought that the configuration of the kinase is altered by its phosphorylated states; by interacting with Na+ and K+ channels, it alters the electrical properties of the membrane to regain the polarized state. Calmodulin is moved to the unphosphorylated kinase to complete the cycle, allowing the voltage-dependent Ca2+ channel to be receptive to Ca2+ flux upon the next cycle of depolarization. Thus, the theory tries to explain (i) why calmodulin and the kinase reside at the postsynaptic density/membrane site, and (ii) what function autophosphorylation of the kinase may play.
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26
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Dunkley PR. Autophosphorylation of neuronal calcium/calmodulin-stimulated protein kinase II. Mol Neurobiol 1991; 5:179-202. [PMID: 1668385 DOI: 10.1007/bf02935545] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A unique feature of neuronal calcium/calmodulin-stimulated protein kinase II (CaM-PK II) is its autophosphorylation. A number of sites are involved and, depending on the in vitro conditions used, three serine and six threonine residues have been tentatively identified as autophosphorylation sites in the alpha subunit. These sites fall into three categories. Primary sites are phosphorylated in the presence of calcium and calmodulin, but under limiting conditions of temperature, ATP, Mg2+, or time. Secondary sites are phosphorylated in the presence of calcium and calmodulin under nonlimiting conditions. Autonomous sites are phosphorylated in the absence of calcium and calmodulin after initial phosphorylation of Thr-286. Mechanisms that lead to a decrease in CaM-PK II autophosphorylation include the thermolability of the enzyme and the activity of protein phosphatases. A range of in vitro inhibitors of CaM-PK II autophosphorylation have recently been identified. Autophosphorylation of CaM-PK II leads to a number of consequences in vitro, including generation of autonomous activity and subcellular redistribution, as well as alterations in conformation, activity, calmodulin binding, substrate specificity, and susceptibility to proteolysis. It is established that CaM-PK II is autophos-phorylated in neuronal cells under basal conditions. Depolarization and/or activation of receptors that lead to an increase in intracellular calcium induces a marked rise in the autophosphorylation of CaM-PK II in situ. The incorporation of phosphate is mainly found on Thr-286, but other sites are also phosphorylated at a slower rate. One consequence of the increase in CaM-PK II autophosphorylation in situ is an increase in the level of autonomous kinase activity. It is proposed that the formation of an autonomous enzyme is only one of the consequences of CaM-PK II autophosphorylation in situ and that some of the other consequences observed in vitro will also be seen. CaM-PK II is involved in the control of neuronal plasticity, including neurotransmitter release and long-term modulation of postreceptor events. In order to understand the function of CaM-PK II, it will be essential to ascertain more fully the mechanisms of its autophosphorylation in situ, including especially the sites involved, the consequences of this autophosphorylation for the kinase activity, and the relationships between the state of CaM-PK II autophosphorylation and the physiological events within neurons.
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Affiliation(s)
- P R Dunkley
- Neuroscience Group, Faculty of Medicine, University of Newcastle, NSW, Australia
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27
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Darlington CL, Flohr H, Smith PF. Molecular mechanisms of brainstem plasticity. The vestibular compensation model. Mol Neurobiol 1991; 5:355-68. [PMID: 1668392 DOI: 10.1007/bf02935558] [Citation(s) in RCA: 52] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
Vestibular compensation is the process of behavioral recovery that occurs following unilateral deafferentation of the vestibular nerve fibers (unilateral labyrinthectomy, UL). Since UL results in a permanent loss of vestibular input from the ipsilateral vestibular (VIIIth) nerve, vestibular compensation is attributed to CNS plasticity and has been used as a general model of lesion-induced CNS plasticity. Behavioral recovery from the ocular motor and postural symptoms of UL is correlated with a partial return of resting activity to neurons in the vestibular nucleus (VN) on the deafferented side (the "deafferented VN"), and lesions to the deafferented VN prevent compensation; therefore, the regeneration of resting activity within the deafferented VN is believed to have a causal role in vestibular compensation. The biochemical mechanisms responsible for the adaptive neuronal changes within the deafferented VN are poorly understood. Neuropeptide hormone fragments, such as adrenocorticotrophic hormone (ACTH)-4-10, have been shown to accelerate vestibular compensation and can act directly on some VN neurons in vitro. Antagonists for the N-methyl-D-aspartate (NMDA) receptor have been shown to inhibit vestibular compensation if administered early in the compensation process. Biochemical studies in frog indicate marked alterations in the phosphorylation patterns of several proteins during compensation, and the in vitro phosphorylation of some of these proteins is modulated by ACTH-(1-24), calcium (Ca2+), and calmodulin or protein kinase C. It is therefore possible that ACTH fragments and NMDA antagonists (via their effects on NMDA receptor-mediated Ca2+ channels) modulate vestibular compensation through their action on Ca(2+)-dependent pathways within VN neurons. Recent studies have shown that some Ca2+ channel antagonists and the Ca(2+)-dependent enzyme inhibitor calmidazolium chloride facilitate vestibular compensation. How the regulation of Ca2+ may be related to the neuronal changes responsible for vestibular compensation is unclear at present.
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Affiliation(s)
- C L Darlington
- Department of Psychology, University of Otago, Dunedin, New Zealand
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