1
|
Gray M, Nash KR, Yao Y. Adenylyl cyclase 2 expression and function in neurological diseases. CNS Neurosci Ther 2024; 30:e14880. [PMID: 39073001 PMCID: PMC11284242 DOI: 10.1111/cns.14880] [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: 05/09/2024] [Revised: 06/25/2024] [Accepted: 07/15/2024] [Indexed: 07/30/2024] Open
Abstract
Adenylyl cyclases (Adcys) catalyze the formation of cAMP, a secondary messenger essential for cell survival and neurotransmission pathways in the CNS. Adcy2, one of ten Adcy isoforms, is highly expressed in the CNS. Abnormal Adcy2 expression and mutations have been reported in various neurological disorders in both rodents and humans. However, due to the lack of genetic tools, loss-of-function studies of Adcy2 are scarce. In this review, we summarize recent findings on Adcy2 expression and function in neurological diseases. Specifically, we first introduce the biochemistry, structure, and function of Adcy2 briefly. Next, the expression and association of Adcy2 in human patients and rodent models of neurodegenerative diseases (Alzheimer's disease and Parkinson's disease), psychiatric disorders (Tourette syndrome, schizophrenia, and bipolar disorder), and other neurological conditions (stress-associated disorders, stroke, epilepsy, and Lesch-Nyhan Syndrome) are elaborated. Furthermore, we discuss the pros and cons of current studies as well as key questions that need to be answered in the future. We hope to provide a focused review on Adcy2 that promotes future research in the field.
Collapse
Affiliation(s)
- Marsilla Gray
- Department of Molecular Pharmacology and Physiology, Morsani College of MedicineUniversity of South FloridaTampaFloridaUSA
| | - Kevin R. Nash
- Department of Molecular Pharmacology and Physiology, Morsani College of MedicineUniversity of South FloridaTampaFloridaUSA
| | - Yao Yao
- Department of Molecular Pharmacology and Physiology, Morsani College of MedicineUniversity of South FloridaTampaFloridaUSA
| |
Collapse
|
2
|
Kleis P, Paschen E, Häussler U, Bernal Sierra YA, Haas CA. Long-term in vivo application of a potassium channel-based optogenetic silencer in the healthy and epileptic mouse hippocampus. BMC Biol 2022; 20:18. [PMID: 35031048 PMCID: PMC8760681 DOI: 10.1186/s12915-021-01210-1] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/08/2021] [Accepted: 12/07/2021] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Optogenetic tools allow precise manipulation of neuronal activity via genetically encoded light-sensitive proteins. Currently available optogenetic inhibitors are not suitable for prolonged use due to short-lasting photocurrents, tissue heating, and unintended changes in ion distributions, which may interfere with normal neuron physiology. To overcome these limitations, a novel potassium channel-based optogenetic silencer, named PACK, was recently developed. The PACK tool has two components: a photoactivated adenylyl cyclase from Beggiatoa (bPAC) and a cAMP-dependent potassium channel, SthK, which carries a large, long-lasting potassium current in mammalian cells. Previously, it has been shown that activating the PACK silencer with short light pulses led to a significant reduction of neuronal firing in various in vitro and acute in vivo settings. Here, we examined the viability of performing long-term studies in vivo by looking at the inhibitory action and side effects of PACK and its components in healthy and epileptic adult male mice. RESULTS We targeted hippocampal cornu ammonis (CA1) pyramidal cells using a viral vector and enabled illumination of these neurons via an implanted optic fiber. Local field potential (LFP) recordings from CA1 of freely moving mice revealed significantly reduced neuronal activity during 50-min intermittent (0.1 Hz) illumination, especially in the gamma frequency range. Adversely, PACK expression in healthy mice induced chronic astrogliosis, dispersion of pyramidal cells, and generalized seizures. These side effects were independent of the light application and were also present in mice expressing bPAC without the potassium channel. Light activation of bPAC alone increased neuronal activity, presumably via enhanced cAMP signaling. Furthermore, we applied bPAC and PACK in the contralateral hippocampus of chronically epileptic mice following a unilateral injection of intrahippocampal kainate. Unexpectedly, the expression of bPAC in the contralateral CA1 area was sufficient to prevent the spread of spontaneous epileptiform activity from the seizure focus to the contralateral hippocampus. CONCLUSION Our study highlights the PACK tool as a potent optogenetic inhibitor in vivo. However, further refinement of its light-sensitive domain is required to avoid unexpected physiological changes.
Collapse
Affiliation(s)
- P Kleis
- Experimental Epilepsy Research, Department of Neurosurgery, Medical Center - University of Freiburg, Faculty of Medicine, 79106, Freiburg, Germany
| | - E Paschen
- Experimental Epilepsy Research, Department of Neurosurgery, Medical Center - University of Freiburg, Faculty of Medicine, 79106, Freiburg, Germany.,Faculty of Biology, University of Freiburg, 79104, Freiburg, Germany
| | - U Häussler
- Experimental Epilepsy Research, Department of Neurosurgery, Medical Center - University of Freiburg, Faculty of Medicine, 79106, Freiburg, Germany.,BrainLinks-BrainTools, University of Freiburg, 79110, Freiburg, Germany
| | - Y A Bernal Sierra
- Experimental Biophysics, Institute of Biology, Humboldt University of Berlin, 10115, Berlin, Germany
| | - C A Haas
- Experimental Epilepsy Research, Department of Neurosurgery, Medical Center - University of Freiburg, Faculty of Medicine, 79106, Freiburg, Germany. .,BrainLinks-BrainTools, University of Freiburg, 79110, Freiburg, Germany. .,Center for Basics in NeuroModulation, Faculty of Medicine, University of Freiburg, 79106, Freiburg, Germany.
| |
Collapse
|
3
|
Mertz C, Krarup S, Jensen CD, Lindholm SEH, Kjær C, Pinborg LH, Bak LK. Aspects of cAMP Signaling in Epileptogenesis and Seizures and Its Potential as Drug Target. Neurochem Res 2019; 45:1247-1255. [PMID: 31414342 DOI: 10.1007/s11064-019-02853-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Revised: 07/30/2019] [Accepted: 08/03/2019] [Indexed: 12/19/2022]
Abstract
Epilepsy is one of the most common chronic neurological conditions. Today, close to 30 different medications to prevent epileptic seizures are in use; yet, far from all patients become seizure free upon medical treatment. Thus, there is a need for new pharmacological approaches including novel drug targets for the management of epilepsy. Despite the fact that a role for cAMP signaling in epileptogenesis and seizures was first suggested some four decades ago, none of the current medications target the cAMP signaling system. The reasons for this are probably many including limited knowledge of the underlying biology and pathology as well as difficulties in designing selective drugs for the different components of the cAMP signaling system. This review explores selected aspects of cAMP signaling in the context of epileptogenesis and seizures including cAMP response element binding (CREB)-mediated transcriptional regulation. We discuss the therapeutic potential of targeting cAMP signaling in epilepsy and point to an increased knowledge of the A-kinase anchoring protein-based signaling hubs as being of seminal importance for future drug discovery within the field. Further, in terms of targeting CREB, we argue that targeting upstream cAMP signals might be more fruitful than targeting CREB itself. Finally, we point to astrocytes as cellular targets in epilepsy since cAMP signals may regulate astrocytic K+ clearance affecting neuronal excitability.
Collapse
Affiliation(s)
- Christoffer Mertz
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Sara Krarup
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Cecilie D Jensen
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Sandy E H Lindholm
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Christina Kjær
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100, Copenhagen, Denmark.,Department of Technology, Faculty of Health and Technology, University College Copenhagen, 2200, Copenhagen, Denmark
| | - Lars H Pinborg
- Epilepsy Clinic & Neurobiology Research Unit, Copenhagen University Hospital, University of Copenhagen, 2100, Copenhagen, Denmark
| | - Lasse K Bak
- Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, 2100, Copenhagen, Denmark.
| |
Collapse
|
4
|
Alves M, Gomez-Villafuertes R, Delanty N, Farrell MA, O'Brien DF, Miras-Portugal MT, Hernandez MD, Henshall DC, Engel T. Expression and function of the metabotropic purinergic P2Y receptor family in experimental seizure models and patients with drug-refractory epilepsy. Epilepsia 2017; 58:1603-1614. [PMID: 28733972 DOI: 10.1111/epi.13850] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/20/2017] [Indexed: 12/14/2022]
Abstract
OBJECTIVE ATP is released into the extracellular space during pathologic processes including increased neuronal firing. Once released, ATP acts on P2 receptors including ionotropic P2X and metabotropic P2Y receptors, resulting in changes to glial function and neuronal network excitability. Evidence suggests an involvement of P2Y receptors in the pathogenesis of epilepsy, but there has been no systematic effort to characterize the expression and function of the P2Y receptor family during seizures and in experimental and human epilepsy. METHODS Status epilepticus was induced using either intra-amygdala kainic acid or pilocarpine to characterize the acute- and long-term changes in hippocampal P2Y expression. P2Y expression was also investigated in brain tissue from patients with temporal lobe epilepsy. Finally, we analyzed the effects of two specific P2Y agonists, ADP and UTP, on seizure severity and seizure-induced cell death. RESULTS Both intra-amygdala kainic acid and pilocarpine-induced status epilepticus increased the transcription of the uracil-sensitive P2Y receptors P2ry2 , P2ry4 , and P2ry6 and decreased the transcription of the adenine-sensitive P2Y receptors P2ry1 , P2ry12 , P2ry13 . Protein levels of P2Y1 , P2Y2 , P2Y4 , and P2Y6 were increased after status epilepticus, whereas P2Y12 expression was decreased. In the chronic phase, P2ry1 , P2ry2 , and P2ry6 transcription and P2Y1 , P2Y2 , and P2Y12 protein levels were increased with no changes for the other P2Y receptors. In hippocampal samples from patients with temporal lobe epilepsy, P2Y1 and P2Y2 protein expression was increased, whereas P2Y13 levels were lower. Demonstrating a functional contribution of P2Y receptors to seizures, central injection of ADP exacerbated seizure severity, whereas treatment with UTP decreased seizure severity during status epilepticus in mice. SIGNIFICANCE The present study is the first to establish the specific hippocampal expression profile and function of the P2Y receptor family after experimental status epilepticus and in human temporal lobe epilepsy and offers potential new targets for seizure control and disease modification.
Collapse
Affiliation(s)
- Mariana Alves
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Rosa Gomez-Villafuertes
- Department of Biochemistry and Molecular Biology IV, Faculty of Veterinary, Complutense University of Madrid, Madrid, Spain
| | - Norman Delanty
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland.,Beaumont Hospital, Beaumont, Dublin, Ireland
| | | | | | - Maria Teresa Miras-Portugal
- Department of Biochemistry and Molecular Biology IV, Faculty of Veterinary, Complutense University of Madrid, Madrid, Spain
| | - Miguel Diaz Hernandez
- Department of Biochemistry and Molecular Biology IV, Faculty of Veterinary, Complutense University of Madrid, Madrid, Spain
| | - David C Henshall
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
| | - Tobias Engel
- Department of Physiology & Medical Physics, Royal College of Surgeons in Ireland, Dublin, Ireland
| |
Collapse
|
5
|
Zhang Y, Gao B, Zheng F, Lu S, Li Y, Xiong Y, Yang Q, Yang Y, Fu P, Xiao F, Wang X. The Phosphodiesterase 10A Inhibitor PF-2545920 Enhances Hippocampal Excitability and Seizure Activity Involving the Upregulation of GluA1 and NR2A in Post-synaptic Densities. Front Mol Neurosci 2017; 10:100. [PMID: 28439226 PMCID: PMC5383654 DOI: 10.3389/fnmol.2017.00100] [Citation(s) in RCA: 12] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Accepted: 03/23/2017] [Indexed: 12/16/2022] Open
Abstract
Phosphodiesterase regulates the homeostasis of cAMP and cGMP, which increase the strength of excitatory neural circuits and/or decrease inhibitory synaptic plasticity. Abnormally, synchronized synaptic transmission in the brain leads to seizures. A phosphodiesterase 10A (PDE10A) inhibitor PF-2545920 has recently attracted attention as a potential therapy for neurological and psychiatric disorders. We hypothesized that PF-2545920 plays an important role in status epilepticus (SE) and investigated the underlying mechanisms. PDE10A was primarily located in neurons, and PDE10A expression increased significantly in patients with temporal lobe epilepsy. PF-2545920 enhanced the hyperexcitability of pyramidal neurons in rat CA1, as measured by the frequency of action potentials and miniature excitatory post-synaptic current. GluA1 and NR2A expression also increased significantly in post-synaptic densities, with or without SE in rats treated with PF-2545920. The ratio of p-GluA1/GluA1 increased in the presence of PF-2545920 in groups with SE. Our results suggest that PF-2545920 facilitates seizure activity via the intracellular redistribution of GluA1 and NR2A in the hippocampus. The upregulation of p-GluA1 may play an important role in trafficking GluA1 to post-synaptic densities. The data suggest it would be detrimental to use the drug in seizure patients and might cause neuronal hyperexcitability in non-epileptic individuals.
Collapse
Affiliation(s)
- Yanke Zhang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical UniversityChongqing, China
| | - Baobing Gao
- Department of Neurology, Chongqing General HospitalChongqing, China
| | - Fangshuo Zheng
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical UniversityChongqing, China
| | - Shanshan Lu
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical UniversityChongqing, China
| | - Yun Li
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical UniversityChongqing, China
| | - Yan Xiong
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical UniversityChongqing, China
| | - Qin Yang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical UniversityChongqing, China
| | - Yong Yang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical UniversityChongqing, China
| | - Pengfei Fu
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical UniversityChongqing, China
| | - Fei Xiao
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical UniversityChongqing, China
| | - Xuefeng Wang
- Department of Neurology, The First Affiliated Hospital of Chongqing Medical UniversityChongqing, China.,Center of Epilepsy, Beijing Institute for Brain DisordersBeijing, China.,Chongqing Key Laboratory of NeurologyChongqing, China
| |
Collapse
|
6
|
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.
Collapse
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.
| |
Collapse
|
7
|
Chen X, Dong G, Zheng C, Wang H, Yun W, Zhou X. A reduced susceptibility to chemoconvulsant stimulation in adenylyl cyclase 8 knockout mice. Epilepsy Res 2015; 119:24-9. [PMID: 26656781 DOI: 10.1016/j.eplepsyres.2015.11.007] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2015] [Revised: 10/18/2015] [Accepted: 11/09/2015] [Indexed: 10/22/2022]
Abstract
OBJECTIVE Adenylyl cyclases (ACs) catalyze the synthesis of cAMP from ATP, and cAMP signaling affects a large number of neuronal processes. Ca(2+)-stimulated adenylyl cyclase 8 (AC8) expressed in the CNS plays a role in synaptic plasticity, drug addiction and ethanol sensitivity, and chronic pain. This study was to aim at examining the contributions of AC8 to epileptogenesis. METHODS In this study, we observed the seizure behavior induced by kainic acid (20 mg/kg or 30 mg/kg) or pilocarpine (350 mg/kg) in AC8 KO and wild-type mice. Next we injected kainic acid or pilocarpine to induce status epilepticus (SE), and examined neuronal degeneration (by Fluoro-Jade B staining) and mossy fiber sprouting (by Timm staining) 24h and 2 weeks after SE termination in the hippocampus, respectively. Finally, 15 min after intraperitoneal injection of kainic acid (30 mg/kg), we examined phosphor-ERK1/2 in the hippocampus by Western blot and immunochemistry staining. RESULTS We first observed that AC8 KO mutants display reduced susceptibility (including seizure latency and episodes) to two chemoconvulsants, kainic acid and pilocarpine. Moreover, we found that degenerative neurons and mossy fiber sprouting induced by chemoconvulsants were significant decreased in the hippocampus. Further, Western blot and immunochemistry analysis revealed that the MAPK signaling in the hippocampus was attenuated in kainic acid-injected AC8 KO mice. CONCLUSION AC8 is involved in epileptogenesis, and may serve as a potential target for the treatment of epilepsy.
Collapse
Affiliation(s)
- Xia Chen
- Laboratory of Neurological Diseases, Department of Neurology, Changzhou No. 2 People's Hospital, The Affiliated Hospital of Nanjing Medical University, Changzhou, Jiangsu Province 213003, China
| | - Guoying Dong
- Laboratory of Neurological Diseases, Department of Neurology, Changzhou No. 2 People's Hospital, The Affiliated Hospital of Nanjing Medical University, Changzhou, Jiangsu Province 213003, China
| | - Changhong Zheng
- Laboratory of Neurological Diseases, Department of Neurology, Changzhou No. 2 People's Hospital, The Affiliated Hospital of Nanjing Medical University, Changzhou, Jiangsu Province 213003, China
| | - Hongbing Wang
- Department of Physiology and Neuroscience Program, Michigan State University, East Lansing, MI 48824, USA
| | - Wenwei Yun
- Laboratory of Neurological Diseases, Department of Neurology, Changzhou No. 2 People's Hospital, The Affiliated Hospital of Nanjing Medical University, Changzhou, Jiangsu Province 213003, China.
| | - Xianju Zhou
- Laboratory of Neurological Diseases, Department of Neurology, Changzhou No. 2 People's Hospital, The Affiliated Hospital of Nanjing Medical University, Changzhou, Jiangsu Province 213003, China.
| |
Collapse
|
8
|
Corticotropin-releasing factor facilitates epileptiform activity in the entorhinal cortex: roles of CRF2 receptors and PKA pathway. PLoS One 2014; 9:e88109. [PMID: 24505399 PMCID: PMC3913751 DOI: 10.1371/journal.pone.0088109] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2013] [Accepted: 01/08/2014] [Indexed: 11/19/2022] Open
Abstract
Whereas corticotropin-releasing factor (CRF) has been considered as the most potent epileptogenic neuropeptide in the brain, its action site and underlying mechanisms in epilepsy have not been determined. Here, we found that the entorhinal cortex (EC) expresses high level of CRF and CRF2 receptors without expression of CRF1 receptors. Bath application of CRF concentration-dependently increased the frequency of picrotoxin (PTX)-induced epileptiform activity recorded from layer III of the EC in entorhinal slices although CRF alone did not elicit epileptiform activity. CRF facilitated the induction of epileptiform activity in the presence of subthreshold concentration of PTX which normally would not elicit epileptiform activity. Bath application of the inhibitor for CRF-binding proteins, CRF6-33, also increased the frequency of PTX-induced epileptiform activity suggesting that endogenously released CRF is involved in epileptogenesis. CRF-induced facilitation of epileptiform activity was mediated via CRF2 receptors because pharmacological antagonism and knockout of CRF2 receptors blocked the facilitatory effects of CRF on epileptiform activity. Application of the adenylyl cyclase (AC) inhibitors blocked CRF-induced facilitation of epileptiform activity and elevation of intracellular cyclic AMP (cAMP) level by application of the AC activators or phosphodiesterase inhibitor increased the frequency of PTX-induced epileptiform activity, demonstrating that CRF-induced increases in epileptiform activity are mediated by an increase in intracellular cAMP. However, application of selective protein kinase A (PKA) inhibitors reduced, not completely blocked CRF-induced enhancement of epileptiform activity suggesting that PKA is only partially required. Our results provide a novel cellular and molecular mechanism whereby CRF modulates epilepsy.
Collapse
|
9
|
Giachello CNG, Premoselli F, Montarolo PG, Ghirardi M. Pentylenetetrazol-induced epileptiform activity affects basal synaptic transmission and short-term plasticity in monosynaptic connections. PLoS One 2013; 8:e56968. [PMID: 23437283 PMCID: PMC3577694 DOI: 10.1371/journal.pone.0056968] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2012] [Accepted: 01/18/2013] [Indexed: 11/18/2022] Open
Abstract
Epileptic activity is generally induced in experimental models by local application of epileptogenic drugs, including pentylenetetrazol (PTZ), widely used on both vertebrate and invertebrate neurons. Despite the high prevalence of this neurological disorder and the extensive research on it, the cellular and molecular mechanisms underlying epileptogenesis still remain unclear. In this work, we examined PTZ-induced neuronal changes in Helix monosynaptic circuits formed in vitro, as a simpler experimental model to investigate the effects of epileptiform activity on both basal release and post-tetanic potentiation (PTP), a form of short-term plasticity. We observed a significant enhancement of basal synaptic strength, with kinetics resembling those of previously described use-dependent forms of plasticity, determined by changes in estimated quantal parameters, such as the readily releasable pool and the release probability. Moreover, these neurons exhibited a strong reduction in PTP expression and in its decay time constant, suggesting an impairment in the dynamic reorganization of synaptic vesicle pools following prolonged stimulation of synaptic transmission. In order to explain this imbalance, we determined whether epileptic activity is related to the phosphorylation level of synapsin, which is known to modulate synaptic plasticity. Using western blot and immunocytochemical staining we found a PTZ-dependent increase in synapsin phosphorylation at both PKA/CaMKI/IV and MAPK/Erk sites, both of which are important for modulating synaptic plasticity. Taken together, our findings suggest that prolonged epileptiform activity leads to an increase in the synapsin phosphorylation status, thereby contributing to an alteration of synaptic strength in both basal condition and tetanus-induced potentiation.
Collapse
|
10
|
Effects of pentoxifylline and H-89 on epileptogenic activity of bucladesine in pentylenetetrazol-treated mice. Eur J Pharmacol 2011; 670:464-70. [PMID: 21946102 DOI: 10.1016/j.ejphar.2011.09.026] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2011] [Revised: 08/31/2011] [Accepted: 09/07/2011] [Indexed: 11/24/2022]
Abstract
The present study shows interactive effects of pentoxifylline (PTX) as a phosphodiesterase (PDE) inhibitor, H-89 as a protein kinase A (PKA) inhibitor and bucladesine (db-cAMP) as a cAMP agonist on pentylenetetrazol (PTZ)-induced seizure in mice. Different doses of pentoxifylline (25, 50, 100 mg/kg), bucladesine (50, 100, 300 nM/mouse), and H-89 (0.05, 0.1, 0.2 mg/100g) were administered intraperitoneally (i.p.), 30 min before intravenous (i.v.) infusion of PTZ (0.5% w/v). In combination groups, the first and second components were injected 45 and 30 min before PTZ infusion. In all groups, the control animals received an appropriate volume of vehicle. Single administration of PTX had no significant effect on both seizure latency and threshold. Bucladesine significantly decreased seizure latency and threshold only at a high concentration (300 nM/mouse). Intraperitoneal administration of H-89 (0.2 mg/100g) significantly increased seizure latency and threshold in PTZ-treated animals. All applied doses of bucladesine in combination with PTX (50 mg/kg) caused a significant reduction in seizure latency. Pretreatment of animals with PTX (50 and 100 mg/kg) attenuated the anticonvulsant effect of H-89 (0.2 mg/100g) in PTZ-exposed animals. H-89 (0.05, 0.2 mg/100g) prevented the epileptogenic activity of bucladesine (300 nM) with significant increase of seizure latency and seizure threshold. In conclusion, we showed that seizure activities were affected by pentoxifylline, H-89 and bucladesine via interactions with intracellular cAMP and cGMP signaling pathways, cyclic nucleotide-dependent protein kinases, and related neurotransmitters.
Collapse
|
11
|
Chang P, Chandler KE, Williams RSB, Walker MC. Inhibition of long-term potentiation by valproic acid through modulation of cyclic AMP. Epilepsia 2009; 51:1533-42. [PMID: 20002144 DOI: 10.1111/j.1528-1167.2009.02412.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
PURPOSE Valproic acid (VPA) is widely used clinically in epilepsy, bipolar disorder, and migraine. In experimental models, it has also been shown to have neuroprotective and antiepileptogenic effects. Its mechanisms of action in these diverse conditions are, however, unclear, but there is some evidence indicating an effect of VPA upon protein kinase A (PKA) activity. We, therefore, asked whether VPA modulates cyclic adenosine monophosphate (cAMP)/PKA-dependent synaptic plasticity and whether this mode of action could explain its anticonvulsant effect. METHODS We first tested the effects of VPA on PKA-dependent synaptic plasticity at mossy fiber to CA3 synapses in rat hippocampus slices following very high-frequency stimulation or application of the adenylyl cyclase activator forskolin. Using biochemical assays, we then tested whether VPA had a direct effect on PKA activity or an indirect effect through modulating cAMP production. Lastly, VPA and inhibitors of adenylyl cyclase (SQ22536) and PKA (H89) were tested in in vitro models of epileptiform activity induced in hippocampal-entorhinal cortex slices using either pentylenetetrazol (2 mM) or low magnesium. RESULTS VPA (1 mm) inhibited PKA-dependent long-term potentiation of mossy fiber to CA3 pyramidal cell transmission. However, VPA did not directly modulate PKA activity but rather inhibited the accumulation of cAMP. In acute in vitro seizure models, the anticonvulsant activity of VPA is not mediated through modulation of adenylyl cyclase or PKA. CONCLUSIONS These results indicate that VPA through an action on cAMP accumulation can inhibit synaptic plasticity, but this cannot fully explain its anticonvulsant effect.
Collapse
Affiliation(s)
- Pishan Chang
- UCL Institute of Neurology, University College London, London, UK
| | | | | | | |
Collapse
|
12
|
Bracey JM, Kurz JE, Low B, Churn SB. Prolonged seizure activity leads to increased Protein Kinase A activation in the rat pilocarpine model of status epilepticus. Brain Res 2009; 1283:167-76. [DOI: 10.1016/j.brainres.2009.05.066] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Revised: 05/27/2009] [Accepted: 05/29/2009] [Indexed: 11/16/2022]
|
13
|
Ure A, Altrup U. Block of spontaneous termination of paroxysmal depolarizations by forskolin (buccal ganglia, Helix pomatia). Neurosci Lett 2005; 392:10-5. [PMID: 16171948 DOI: 10.1016/j.neulet.2005.08.045] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2005] [Revised: 08/11/2005] [Accepted: 08/22/2005] [Indexed: 11/19/2022]
Abstract
Effects of cAMP-activated protein kinases (PKA) on epileptic activity are at present studied in a model nervous system. Identified neurons in the buccal ganglia of the snail Helix pomatia were recorded with intracellular microelectrodes in a continuously perfused experimental chamber. Epileptiform activity appeared regularly in neuron B3 when the saline contained pentylenetetrazol (20-40 mM). Epileptiform activity consisted of a series of paroxysmal depolarization shifts (PDS). Epileptiform activity was quantified by calculating the percentage of PDS-duration of PDS-periods. High percentage of PDS-duration was regularly found 15-30 min after the start of treatment with pentylenetetrazol. Subsequently, percentage of PDS decreased spontaneously. Adding forskolin (50 microM) to the pentylenetetrazol-containing solution increased percentage of PDS-duration. The increase during forskolin corresponded to the amount of decrease which had taken place spontaneously before. During application of forskolin for up to 4 h, spontaneous PDS decrease was absent, i.e., epileptiform activity corresponded to status epilepticus. Forskolin was not able to induce epileptiform activity when applied without pentylenetetrazol. 1,6-Dideoxy-forskolin (50 microM) did not accelerate epileptiform activity. When pentylenetetrazol was applied twice (1 h each) separated by 2.5 h of control conditions, PDS decrease obtained during the first application was found to be largely preserved during control conditions. When forskolin was applied for 30 min in between both applications of pentylenetetrazol, the second response to pentylenetetrazol did not show a preserved PDS decrease. Results suggest that forskolin blocks an endogenous antiepileptic process and that activation of PKA can maintain epileptic activity and induce status epilepticus.
Collapse
Affiliation(s)
- Atik Ure
- Institute of Experimental Epilepsy Research, University of Münster, Hüfferstrabe 68, Germany
| | | |
Collapse
|
14
|
Okada M, Zhu G, Yoshida S, Hirose S, Kaneko S. Protein kinase associated with gating and closing transmission mechanisms in temporoammonic pathway. Neuropharmacology 2005; 47:485-504. [PMID: 15380368 DOI: 10.1016/j.neuropharm.2004.04.019] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2003] [Revised: 01/31/2004] [Accepted: 02/16/2004] [Indexed: 10/26/2022]
Abstract
The entorhinal cortex (EC) is a major source of afferent input to the hippocampus via the perforant and temporoammonic pathways; however, the detailed transmission mechanism in the temporoammonic pathway remains to be clarified. Thus, we determined interaction among GABA(A), AMPA/glutamate receptors and protein kinases (PKA and PKC) in the exocytosis of GABA and glutamate using multiprobe microdialysis, as well as propagation of neuronal excitability using optical recording in the EC-Hippocampal formation. Multiprobe microdialysis demonstrated that EC-evoked GABA release in ventral CA1 was predominantly regulated by the PKC-related rather than PKA-related exocytosis mechanism and was augmented by the activation of glutamatergic transmission. Contrary to GABA release, EC-evoked glutamate release was predominantly regulated by PKA-related rather than PKC-related mechanisms and was suppressed by activation of GABAergic transmission. Optical recording demonstrated that there are two sub-pathways in the temporoammonic pathway; direct projects from EC layers (II-IV) to dendrites on pyramidal cells and GABAergic interneurons in ventral hippocampal CA1. PKC activation enhanced trisynaptic transmission, whether the GABA(A) receptor was functional or blocked, whereas PKC activation enhanced and inhibited temporoammonic transmission when the GABA(A) receptor was functional and blocked, respectively. Thus, GABAergic inhibition, which is regulated by PKC activity, in the temporoammonic pathway is more significant than that in the trisynaptic pathway.
Collapse
Affiliation(s)
- Motohiro Okada
- Department of Neuropsychiatry, Hirosaki University, Zaifu-cho 5, Hirosaki 036-8562, Japan.
| | | | | | | | | |
Collapse
|
15
|
The role of the hyperpolarization-activated cationic current I(h) in the timing of interictal bursts in the neonatal hippocampus. J Neurosci 2003. [PMID: 12736337 DOI: 10.1523/jneurosci.23-09-03658.2003] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Under both pathological and experimental conditions, area CA3 of the adult or juvenile hippocampus generates periodic population discharges known as interictal bursts. Whereas the ionic and synaptic basis of individual bursts has been comprehensively studied experimentally and computationally, the pacemaker mechanisms underlying interictal rhythmicity remain conjectural. We showed previously that rhythmic population discharges resembling interictal bursts can be induced in hippocampal slices from first postnatal week mice, in Mg2+-free solution with GABA(A) receptor-mediated inhibition blocked. Here we show that these neonatal bursts occurred with high temporal precision and that their frequency and regularity were greatly reduced by the bradycardic agent ZD-7288 when applied at concentrations and durations that selectively block the hyperpolarization-activated, cationic current I(h). Augmenting I(h) by elevating intracellular cAMP dramatically increased burst frequency in a protein kinase A-independent manner. Burst amplitudes were strongly correlated with the preceding, but not the following, interburst intervals. The experimentally observed distribution of interburst intervals was modeled by assuming that a burst was triggered whenever the instantaneous rate of spontaneous EPSPs (sEPSPs) exceeded a threshold and that the mean sEPSP rate was minimal immediately after a burst and then relaxed exponentially to a steady-state level. The effect of blocking I(h) in any given slice could be modeled by decreasing only the steady-state sEPSP rate, suggesting that the instantaneous rate of sEPSPs is governed by the level of I(h) activation and raising the novel possibility that interburst intervals reflected the slow activation kinetics of I(h) in the neonatal CA3.
Collapse
|
16
|
Rubaj A, Zgodzinski W, Gustaw K, Sieklucka-Dziuba M. Nociceptin, OP4 receptor ligand in different models of experimental epilepsy. Peptides 2002; 23:497-505. [PMID: 11835999 DOI: 10.1016/s0196-9781(01)00636-2] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The anticonvulsive activity of nociceptin, endogenous OP4 receptors agonist was investigated in pentylenetetrazole (PTZ), N-methyl D-aspartic acid (NMDA), bicucculine (BCC) and electrically evoked seizure models of experimental epilepsy. Nociceptin, at the dose of 10 nmol, suppressed the clonic seizures induced by PTZ, NMDA and BCC. [Phe1(psi)(CH2-NH)Gly2]nociceptin-(1-13)-NH2 which has been proposed to be selective antagonist OP4 receptors, did not prevent the action of nociceptin. The effect of [Phe1(psi)(CH2-NH)Gly2]nociceptin-(1-13)-NH2 on seizures induced by PTZ, NMDA and BCC was very similar to that of nociceptin. These data support the hypothesis that it possesses agonistic properties. Naloxone did not reverse the anticonvulsive action of nociceptin as well as [Phe1(psi)(CH2-NH)Gly2]nociceptin-(1-13)-NH2 which excludes the participation of opioid receptor in this action. On the other hand in the electroconvulsive model of generalized seizures, nociceptin as well as [Phe1(psi)(CH2-NH)Gly2]nociceptin-(1-13)-NH2 influenced neither the electroconvulsive threshold nor the maximal electroshock test. The data suggest that nociceptin and [Phe1(psi)(CH2-NH)Gly2]nociceptin-(1-13)-NH2 can exert anticonvulsive action. These properties depend on OP4 but not opioid receptors activation.
Collapse
Affiliation(s)
- Andrzej Rubaj
- Department of Cardiology, Medical University of Lublin, Jaczewskiego 8, 20-090, Lublin, Poland
| | | | | | | |
Collapse
|
17
|
Imamura K, Kasamatsu T, Shirokawa T, Ohashi T. Restoration of ocular dominance plasticity mediated by adenosine 3',5'-monophosphate in adult visual cortex. Proc Biol Sci 1999; 266:1507-16. [PMID: 10467742 PMCID: PMC1690167 DOI: 10.1098/rspb.1999.0808] [Citation(s) in RCA: 20] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Noradrenaline (NA)-stimulated beta-adrenoreceptors activate adenylate cyclase via excitatory G-proteins (Gs). Activated adenylate cyclase in turn promotes the production of cAMP. Critical roles of cAMP-dependent protein kinase A (PKA) in divergent cellular functions have been shown, including memory, learning and neural plasticity. Ocular dominance plasticity (ODP) is strongly expressed in early postnatal life and usually absent in the mature visual cortex. Here, we asked whether the activation of cAMP-dependent PKA could restore ODP to the aplastic visual cortex of adult cats. Concurrent with brief monocular deprivation, each of the following cAMP-related drugs was directly and continuously infused in the adult visual cortex: cholera toxin (a Gs-protein stimulant), forskolin (a Gs-protein-independent activator of adenylate cyclase) and dibutyryl cAMP (a cAMP analogue). We found that the ocular dominance distribution became W-shaped, the proportion of binocular cells being significantly lower than that in respective controls. We concluded that the activation of cAMP cascades rapidly restores ODP to the adult visual cortex, though moderately. The finding further extends the original hypothesis that the NA-beta-adrenoreceptors system is a neurochemical mechanism of cortical plasticity.
Collapse
Affiliation(s)
- K Imamura
- Subfemtomole Biorecognition Project, Japan Science and Technology Corporation, Osaka, Japan
| | | | | | | |
Collapse
|
18
|
Cross-modulation of synaptic plasticity by beta-adrenergic and 5-HT1A receptors in the rat basolateral amygdala. J Neurosci 1999. [PMID: 9880577 DOI: 10.1523/jneurosci.19-02-00570.1999] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Neurotransmitter receptors are often colocalized in a neuron with other receptors, and activation of one receptor can either amplify or antagonize the response to a colocalized receptor. The aim of this study was to investigate the cross-regulation of synaptic transmission by beta-adrenergic and serotonin 1A (5-HT1A) receptors and to elucidate their underlying mechanisms. Stimulation of presynaptic beta-adrenergic receptors with isoproterenol (Iso) in the basolateral amygdala resulted in a long-lasting increase in synaptic transmission. This effect was mimicked by forskolin, an activator for adenylyl cyclase and a cAMP analog. In addition, the effect of forskolin was blocked by catalytic and regulatory site antagonists for cAMP-dependent protein kinase (PKA), indicating a PKA-mediated mechanism. Application of 5-HT depressed the synaptic transmission and blocked Iso- and forskolin-induced potentiation. The effect of 5-HT was mimicked by the selective 5-HT1A agonist 8-hydroxy-dipropylaminotetralin and was blocked by the selective 5-HT1A antagonist 1-(2-methoxyphenyl)-4[4-(2-phthalimido)butyl]piperazine, indicating its mediation by 5-HT1A receptors. To determine the locus of interaction, Sp-cAMPS, a membrane-permeable activator of PKA, was applied, and the potentiation produced by Sp-cAMPS was completely blocked in slices pretreated with 5-HT. These results suggest that the interaction between the intracellular signaling pathways activated by 5-HT1A and beta-adrenergic receptors occurs at a step downstream from cAMP production.
Collapse
|
19
|
Skradski SL, White HS, Ptácek LJ. Genetic mapping of a locus (mass1) causing audiogenic seizures in mice. Genomics 1998; 49:188-92. [PMID: 9598305 DOI: 10.1006/geno.1998.5229] [Citation(s) in RCA: 32] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022]
Abstract
Frings audiogenic seizure-susceptible mice are a model for sensory-evoked reflex seizures. Their seizure phenotype is characterized by wild running, loss of righting reflex, tonic flexion, and tonic extension in response to high-intensity sound stimulation. The Frings mice represent an inbred colony that has not been genetically characterized. This investigation studied the mode of inheritance for audiogenic seizures by crossing the Frings mouse with the seizure-resistant C57BL/6J mouse. Among the backcross progeny generated by crossing (Frings x C57BL/6J)F1 mice with the Frings strain, 391 of the 836 N2 progeny were audiogenic seizure susceptible, a finding consistent with monogenic inheritance. Genetic mapping and linkage analysis of hybrid mice using MIT microsatellite marker sequences localized the seizure gene, named mass1 for monogenic audiogenic seizure susceptible, to an approximately 3.6 cM interval in the middle of mouse chromosome 13. Linkage of mass1 to chromosome 13 is an important step in identifying the gene associated with a monogenic seizure disorder in mice, which may ultimately lead to a better understanding of the pathophysiology of human seizure disorders.
Collapse
Affiliation(s)
- S L Skradski
- Department of Pharmacology and Toxicology, University of Utah, Salt Lake City 84112, USA
| | | | | |
Collapse
|
20
|
Apland JP, Helekar SA, Lebeda FJ. Suppression of drug-induced epileptiform discharges by cyclic AMP in rat hippocampus. MOLECULAR AND CHEMICAL NEUROPATHOLOGY 1997; 31:265-78. [PMID: 9336768 DOI: 10.1007/bf02815129] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/05/2023]
Abstract
The effect of cyclic adenosine 3',5'-monophosphate (cAMP) on epileptiform activity in rat hippocampal slices was investigated. Bath-applied cAMP reversibly decreased the frequency of extracellularly recorded discharges in the CA3 subfield induced by bethanechol- or theophylline-containing solutions. Because cAMP was presumed to be relatively membrane impermeant, we developed and tested the hypothesis that this cAMP-mediated effect occurred extracellularly through the catabolic conversion of cAMP to 5'-AMP and, in turn, to adenosine, a known inhibitory neuromodulator. Three predictions derived from this catabolic hypothesis were tested. First, blockers of the enzymes involved were predicted to antagonize this effect of cAMP. In contrast, the coapplication of a cAMP-phosphodiesterase inhibitor, 3-isobutyl-1-methylxanthine (IBMX), or a 5'-nucleotidase inhibitor, adenosine 5'-[alpha, beta-methylene] diphosphate (AMP-CP), enhanced the cAMP-induced suppressive effect. Second, the nonhydrolyzable cAMP analogs, dibutyryl- and 8-bromo-cAMP, were predicted to be ineffective. Low concentrations (5-40 microM) of these two derivatives, however, also suppressed bethanechol-induced discharges, while, at a higher concentration (100 microM), both analogs increased discharge frequencies. Third, enzymatic catabolism of adenosine was predicted to antagonize cAMP's effect, but coapplying adenosine deaminase (10 U/mL) did not diminish this action. Because these data did not support the catabolic hypothesis, other, as yet undefined, mechanisms must be responsible for the discharge-suppressant effect of cAMP.
Collapse
Affiliation(s)
- J P Apland
- Neurotoxicology Branch, US Army Medical Research Institute of Chemical Defense, Aberdeen Proving Ground, MD 21010-5425, USA.
| | | | | |
Collapse
|
21
|
Epileptogenesis in vivo enhances the sensitivity of inhibitory presynaptic metabotropic glutamate receptors in basolateral amygdala neurons in vitro. J Neurosci 1997. [PMID: 8994053 DOI: 10.1523/jneurosci.17-03-00983.1997] [Citation(s) in RCA: 67] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Modulation of excitatory synaptic transmission by presynaptic metabotropic glutamate receptors (mGluRs) was examined in brain slices from control rats and rats with amygdala-kindled seizures. Using whole-cell voltage-clamp and current-clamp recordings, this study shows for the first time that in control and kindled basolateral amygdala neurons, two pharmacologically distinct presynaptic mGluRs mediate depression of synaptic transmission. Moreover, in kindled neurons, agonists at either group II- or group III-like mGluRs exhibit a 28- to 30-fold increase in potency and suppress synaptically evoked bursting. The group II mGluR agonist (2S,3S,4S)-2-(carboxycyclopropyl)glycine (L-CCG) dose-dependently depressed monosynaptic EPSCs evoked by stimulation in the lateral amygdala with EC50 values of 36 nM (control) and 1.2 nM (kindled neurons). The group III mGluR agonist L-2-amino-4-phosphonobutyrate (L-AP4) was less potent, with EC50 values of 297 nM (control) and 10.8 nM (kindled neurons). The effects of L-CCG and L-AP4 were fully reversible. Neither L-CCG (0.0001-10 microM) nor L-AP4 (0.001-50 microM) caused membrane currents or changes in the current-voltage relationship. The novel mGluR antagonists (2S,3S,4S)-2-methyl-2-(carboxycyclopropyl)-glycine (MCCG; 100 microM) and (S)-2-methyl-2-amino-4-phosphonobutyrate (MAP4; 100 microM) selectively reversed the inhibition by L-CCG and L-AP4 to 81.3 +/- 12% and 65.3 +/- 6.6% of predrug, respectively. MCCG and MAP4 (100-300 microM) themselves did not significantly affect synaptic transmission. The exquisite sensitivity of agonists in the kindling model of epilepsy and the lack of evidence for endogenous receptor activation suggest that presynaptic group II- and group III-like mGluRs might be useful targets for suppression of excessive synaptic activation in neurological disorders such as epilepsy.
Collapse
|