Author Hanaya R, Sasa M, Kiura Y, Serikawa T, Kurisu K.
Title Effects of vigabatrin on epileptiform abnormal discharges in hippocampal CA3 neurons of spontaneously epileptic rats (SER).
Journal Epilepsy Res.
Abstract Vigabatrin, a gamma-amino butyric acid (GABA) transaminase inhibitor, is known to inhibit partial epilepsy in humans. The spontaneously epileptic rat (SER), a double mutant (zi/zi, tm/tm), exhibits both tonic convulsion and absence-like seizures from the age of 8 weeks. Hippocampal CA3 pyramidal neurons in SER show a long-lasting depolarization shift with accompanying repetitive firing when a single stimulus is delivered to the mossy fibers in slice preparations. The effects of vigabatrin on the abnormal excitability of hippocampal CA3 pyramidal neurons in SER were examined to elucidate the mechanism underlying the antiepileptic action of the drug. Intracellular recordings were performed in 24 hippocampal slice preparations of 20 SER aged 8-17 weeks old. Bath application of vigabatrin (1 mM) inhibited the depolarizing shifts with repetitive firing induced by mossy fiber stimulation in 15 min without affecting the first spike and resting membrane potentials in hippocampal CA3 neurons of SER. A higher dose of vigabatrin (10 mM) sometimes inhibited the first spike. However, vigabatrin at doses up to 10 mM did not significantly affect the single action potential elicited by stimulation of the mossy fibers in the hippocampal CA3 neurons of age-matched Wistar rats. In addition, application of vigabatrin (10 mM) did not significantly affect the firing induced by depolarizing pulse applied in the CA3 neurons of the SER, nor the miniature excitatory postsynaptic potential (mEPSP) recorded in the CA3 neurons of SER. The inhibitory effect of vigabatrin (1 mM) on the mossy fiber stimulation-induced depolarization shift with repetitive firing was blocked by concomitant application of bicuculline (10 microM), a GABA(A) receptor antagonist. These findings strongly suggested that GABA increased by inhibition of GABA transaminase with vigabatrin inhibits abnormal excitation of hippocampal CA3 neurons of SER via GABA(A) receptors, although the possibility that the drug acted directly on the GABA(A) receptors of CA3 neurons could not be completely excluded.
Volume 50(3)
Pages 223-31
Published 2002-8
PII S0920121102000025
PMID 12200213
MeSH Action Potentials / drug effects Analysis of Variance Animals Anticonvulsants / pharmacology* Bicuculline / pharmacology Epilepsy / physiopathology* Excitatory Postsynaptic Potentials / drug effects Excitatory Postsynaptic Potentials / physiology Female GABA Antagonists / pharmacology Hippocampus / drug effects* Hippocampus / physiopathology Male Membrane Potentials / drug effects Mossy Fibers, Hippocampal / drug effects Mossy Fibers, Hippocampal / physiopathology Neurons / drug effects* Neurons / physiology Rats Rats, Inbred WKY Rats, Mutant Strains Receptors, GABA-A / drug effects Receptors, GABA-A / physiology Vigabatrin / pharmacology*
IF 2.178
Times Cited 4