Extrasynaptic Release of GABA by Retinal Dopaminergic Neurons

TL;DRAbstract

GABA release by dopaminergic amacrine (DA) cells of the mouse retina was detected by measuring Cl- currents generated by isolated perikarya in response to their own neurotransmitter. The possibility that the Cl- currents were caused by GABA release from synaptic endings that had survived the dissociation of the retina was ruled out by examining confocal Z series of the surface of dissociated tyrosine hydroxylase-positive perikarya after staining with antibodies to pre and postsynaptic markers. GABA release was caused by exocytosis because 1) the current events were transient on the millisecond time scale and thus resembled miniature synaptic currents; 2) they were abolished by treatment with a blocker of the vesicular proton pump, bafilomycin A1; and 3) their frequency was controlled by the intracellular Ca2+ concentration. Because DA cell perikarya do not contain presynaptic active zones, release was by necessity extrasynaptic. A range of depolarizing stimuli caused GABA exocytosis, s

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