A Study on Ca Influx and Acetyulcholine Release in the Presynaptic Terminals of Cholinergic Nerve of the Electric Organ

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(1)There exist N-, P/Q- and L-type voltage-dependent Ca channels (VDCCs) in the presynaptic plasma membranes of nerve terminals of the electric organ isolated from the Japanese electric ray Narke japonica. The acetylcholine (ACh) release was predominantly mediated by-and P/Q-type VDCCs. (2)cDNA for synaphine was cloned from the cDNA library prepared from the electric lobe of the ray. Synaphine was found to be associated with syntaxin, VAMP and SNAP-25, suggesting its involvement in the exocytosis. (3)cDNA for the Alzheimer's beta-amyolid presursor protein (APP) was also isolated from the above cDNA library. The analysis indicated the product protein, APP,was phosphorylated after its maturation. (4)There exist adenosine A_1 and A_<2B> receptors in the electric organ synaptic membrane. Activation of the latter increses the ACh release via potentiation of P/Q-type VDCCs while the activation of the former reduces the ACh release via inhibition of N-type VDCCs. (5)Antibodies from the lambert-Eaton syndrome (LES) patients reduced the ACh release by its specific down-regulation of P/Q-type VDCCs. (6)Immunization of rats or mice with the electric organ synaptosomes produced an animal model of LES.