Immunocytochemical evidence that vigabatrin in rats causes GABA accumulation in glial cells of the retina.

Vigabatrin (gamma-vinyl-GABA, GVG) is an irreversible inhibitor of GABA-aminotransferase (GABA-T) that is under clinical trial as an antiepileptic drug. Rats were injected (i.p.) with GVG and killed 18 h later. GVG administration reduced retinal GABA-T activity to undetectable levels and increased the GABA content 5-fold. Immunocytochemistry using a GABA antiserum clearly revealed the presence of GABA-IR in the glial Muller cells of retinas from GVG-treated rats but not from controls. This experiment indicates that the administration of drugs which inhibit GABA-T may cause the accumulation of GABA in retinal cells that do not normally possess enough endogenous GABA to be detected by immunocytochemistry.