Potent and stereospecific anticonvulsant activity of 3-isobutyl GABA relates to in vitro binding at a novel site labeled by tritiated gabapentin.

3-Isobutyl GABA is a derivative of the inhibitory neurotransmitter gamma-aminobutyric acid (GABA) and is also structurally related to the novel anticonvulsant gabapentin. The S(+) enantiomer of 3-isobutyl GABA blocks maximal electroshock seizures in mice and also potently displaces tritiated gabapentin from a novel high-affinity binding site in rat brain membrane fractions. The R(-) enantiomer is much less active in both assays, suggesting that the gabapentin binding site is involved in the anticonvulsant activity of 3-isobutyl GABA.