The differential release of amino acids and neuropeptides from purified subpopulations of mammalian GABAergic and cholinergic cerebrocortical synaptosomes.

GABAergic and cholinergic synaptosome populations were isolated by immunomagnetophoresis. Analysis of 8 amino acids showed that the GABAergic population was enriched in GABA (3 fold). The cholinergic population was enriched in citrulline (5 fold). CCK was found in both populations, but was enriched in the GABAergic. No monoamines were found in either subpopulation. Stimulated release (veratridine 50 microns), measured using a superfusion system, showed that glutamate was only released from the cholinergic subpopulation, as was VIP. In the GABAergic population, stimulated SRIF release was slow and prolonged, and the CCK release was delayed and rapid. GABA release was rapid, only occurring during application of the stimulus and only from the GABAergic synaptosomes. The GABAergic release could be modified by GABAA and GABAB targeted drugs. The cholinergic subpopulation exhibited late release of both VIP and CCK, each showing the same time pattern of release. All release was calcium and tetrodotoxin dependent.