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Presynaptic inhibition of excitatory neurotransmission by lamotrigine in the rat amygdalar neurons
Author(s) -
Wang SuJane,
Huang ChiungChun,
Hsu KueiSen,
Tsai JingJane,
Gean PoWu
Publication year - 1996
Publication title -
synapse
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.809
H-Index - 106
eISSN - 1098-2396
pISSN - 0887-4476
DOI - 10.1002/(sici)1098-2396(199611)24:3<248::aid-syn7>3.0.co;2-e
Subject(s) - cnqx , chemistry , excitatory postsynaptic potential , neurotransmission , ampa receptor , nmda receptor , channel blocker , bicuculline , pharmacology , postsynaptic potential , neuroscience , biophysics , antagonist , receptor , biochemistry , biology , calcium , organic chemistry
Lamotrigine (LAG) is a new antiepileptic drug which is licensed as adjunctive therapy for partial and secondary generalized seizures. In the present study, the mechanisms responsible for its antiepileptic effect were studied in rat amygdaloid slices using intracellular recording and whole‐cell patch clamp techniques. Bath application of LAG (50 μM) reversibly suppressed the excitatory postsynaptic potentials (EPSPs) and currents (EPSCs) evoked by stimulating ventral endopyriform nucleus. Synaptic response mediated by the N‐methyl‐D‐aspartate (NMDA) receptor (EPSP NMDA ) was isolated pharmacologically by application of a solution containing non‐NMDA receptor antagonist 6‐cyano‐7‐nitroquinoxaline‐2,3‐dione (CNQX,10 μM) and γ‐aminobutyric acid A receptor antagonist bicuculline (20 μM). LAG produced a parallel inhibition of EPSP NMDA . Postsynaptic depolarization induced by α‐amino‐5‐methyl‐4‐isoxazole propionate (AMPA) was not altered by LAG. In addition, LAG increased the ratio of the second pulse response to the first pulse response (P 2 /P 1 ), which is consistent with a presynaptic mode of action. The L‐type Ca ++ channel blocker nifedipine (20 μM) had no effect on LAG‐induced presynaptic inhibition. However, the depressant effect of LAG was markedly reduced in slices pretreated with N‐type Ca ++ channel blocker ωconotoxin‐GVIA (ω‐CgTX‐GVIA, 1 μM) or a broad spectrum Ca ++ channel blocker ω‐conotoxin‐MVIIC (ω‐CgTX‐MVIIC, 1 μM). It is concluded that a reduction in ω‐CgTX‐GVIA‐sensitive Ca ++ currents largely contributes to LAG‐induced presynaptic inhibition. © 1996 Wiley‐Liss, Inc.