Indexed on: 01 Oct '79Published on: 01 Oct '79Published in: Neurochemical Research
The effects were investigated of purified subsynaptic fractions on the efflux of radioactivity from a plain synaptic vesicle fraction which had incorporated [3H]dopamine. About 50% of the radioactivity incorporated into the plain vesicles (120 μg protein) was liberated on exposure to purified synaptic membranes (30 μg protein). The synaptic membrane-dependent efflux appeared to depend on both adenosine triphosphate and divalent cations, especially Ca2+. Of the subcellular fractions used, the heavy microsomal fraction showed the same effects as the synaptic membrane fraction. Purified synaptic junctions exhibited the strongest stimulating effects: the efflux was 2 times greater than that observed with synaptic membranes. The stimulating effects of myelin were less than oneseventh of those of synaptic junctional fraction. These observations may indicate that the transmitters are liberated by interaction of vesicle membrane with synaptic membrane in the presence of ATP and divalent cations.