GENE-BASED NEUROTRANSMITTER MODULATION IN CEREBELLAR GRANULE NEURONS

The human glutamic acid decarboxylase (GAD) gene was transferred into rat cerebellar granule neurons. Following adenoviral-mediated gene tra nsfer, nearly 100% of the neurons had transgene expression that persis ted for the duration of their survival in culture, GABA levels were el evated both in the growth media and in lysates of GAD-modified granule neurons. In GAD-modified neurons, extracellular GABA levels steadily increased with time, whereas intracellular GABA levels peaked 10 days after gene transfer. GAD-modified neurons released both glutamate and GABA into the surrounding media before and after potassium-induced sti mulation, but only the release of glutamate was sensitive to potassium stimulation. These data suggest that glutamatergic neurons, which ini tially contained no detectable GABA, can be genetically modified to re lease GABA constitutively.