The trophic effect of gaba on cerebellar granule cells is mediated by gaba-receptors.

The effect of GABA, its agonist THIP (4,5,6,7-tetrahydroisoxazolo[5,4-c]pyridin-3-ol), and its antagonist bicuculline methobromide on the ultrastructure of cerebellar granule cells was studied. It was found that while the density of mitochondria, the ribosomes and smooth endoplasmic reticulum was unaffected by this treatment the density of neurotubules, rough endoplasmic reticulum, Golgi apparatus and coated as well as other vesicles was greatly enhanced by treatment of the cultured neurons with GABA (50 μM) or THIP (150 μM). The effects of GABA could be completely blocked by the simultaneous presence of bicuculline methobromide (150 μM) in the culture media. The findings strongly suggest that the trophic action of GABA is mediated by GABA receptors and not by an intracellular action of GABA.