February 25 Highlights

Abstract

Gambardella et al. report a genetic association between nonlesional temporal lobe epilepsy (TLE) and a missense (G1465A) polymorphism in the GABA (B) receptor gene. Moreover, patients carrying the GABA (B) G1465A polymorphism are also reported to have an increased odds of developing drug refractory TLE. see page 560 Commentary from Michael R. Johnson New antiepileptic drug development will be made possible by better understanding of molecular mechanisms underlying epilepsy. Genetic influences on γ-aminobutyric acid (GABA) are likely to be of importance. The report from Gambardella et al. in this issue of Neurology provides novel evidence concerning a GABA receptor and temporal lobe epilepsy. The neuronal response to GABA has two phases. Inotropic (GABAA) receptors produce a rapid, chloride - mediated postsynaptic membrane hyperpolarization. Metabotropic (GABAB) receptors generate a long lasting, G-protein–mediated, inhibitory hyperpolarization of postsynaptic membranes as well as inhibition of neurotransmitter release from presynaptic terminals. The GABAA receptor is a heteromeric complex of subunits including α1-6, β13-3, γ13, δ e, and π.1 GABAB receptors comprise a heterodimer of GABABR1 and GABABR2 subunits, with R1 providing the binding domain and R2 responsible for second messenger processing.2 A central role for GABAA receptors in epilepsy, long suspected from pharmacologic studies, was firmly established with the identification of mutations in γ2(GABRG2) and α1 (GABRA1) subunits in familial generalized epilepsy.3-5 …