GABA influences the ultrastructure composition of cerebellar granule cells during development in culture

The influence of GABA on cerebellar granule cells in culture was followed morphometrically during in vitro development by growing the cells in the absence or presence of 50 μM GABA. The presence of GABA in the culture media increased the number of neurite-extending cells by 50% after 7 days in culture. At the ultrastructural level GABA treatment led to an increased density of neurotubules, rough endoplasmic reticulum, Golgi apparatus, coated vesicles and other vesicles, whereas structures such as mitochondria and smooth endoplasmic reticulum were not affected by GABA. The density of free ribosomes showed a more pronounced tendency to decrease as a function of the culture period (1-7 days) when the cells were grown in the presence of GABA as compared to control cultures. The results strongly indicate that GABA in addition to being an important neurotransmitter serves as a trophic factor in the development of at least certain types of neurons.