GABA

Isoguvacine binds to a mouse forebrain synaptic membrane preparation. The specific binding is displaceable by GABA, muscimol and bicuculline but not by picrotoxin or diaminobutyric acid. Kinetic data suggest two binding affinities. Highest levels of binding are observed in the cerebellum, cortex and hippocampus. Isoguvacine binds to membrane preparations of rat forebrain with pharmacological characteristics similar to the postsynaptic GABA recognition site: that it is transported into synaptosomal preparations by an uptake system similar to the high-affinity GABA uptake system; and that recently accumulated isoguvacine is released in a Ca ²⁺ -dependent manner and by heteroexchange with external GABA. Isoguvacine at a concentration of 50 μM blocks the seizure like events in 2 out of 6 organotypic hippocampal slice cultures. Isoguvacine inhibits the low magnesium induced seizure like events dose dependently.