cerebellar giant synaptosomes: a model to study basal and stimulated release of [3h]gamma-aminobutyric acid

background: neurotransmitter release is an essential link in cell communication of the nervous system. many investigations have focused on gamma amino butyric acid (gaba)-ergic neurotransmission, because it has been implicated in the pathophysiology of several central nervous system disorders. to bypass complications related to homo- and heterosynaptic modulation and to avoid indirect interpretations of data, we herein describe a simple approach for direct measurement of gaba release.   material and methods: giant synaptosomes originated from nerve terminals of rat cerebellum mossy fibers were prepared for the study. electron micrographs as well as lactate dehydrogenase assay are used for morphological and biochemical verifications. giant synaptosomes were preloaded with labeled [ 3 h]gaba. spontaneous and stimulated release of [ 3 h]gaba was measured using a superfusion apparatus. stimulation was evoked by increasing exteracellular concentration of k + ions.   results: spontaneous [ 3 h]gaba release had a constant and nearly linear kinetics. [ 3 h]gaba outflow evoked by depolarizing solution containing 15 mm of k + showed 2-3 fold increases over the basal release. the same effect was also reproducible after several minutes.   conclusion: the present findings indicate that this preparation could be used as a suitable and versatile in vitro model to study gaba release from axon terminals under basal and evoked conditions. iran j med sci 2005 ; 30(1): 16-20.   keywords ● synaptosome ● neurotransmitter release ● cerebellum ● gaba