Neurosecretion of transmitter substance is a cellular process whereby information transfer occurs in the nervous system. Thus, normal nervous system signaling and resultant behavior depend upon an orderly and closely regulated release mechanism for these transmitters. This neurosecretory machinery is present at every chemical synapse in the organism. Many neurological disorders and psychiatric conditions are thought to involve disturbances in neurotransmission, thus clear and detailed knowledge of this subject at a molecular level holds promise for identifying the basis for rational therapeutic strategies. This research, will clarify, in terms of individual quanta of transmitter released, the final steps in exocytosis of neurotransmitter vesicles. It is well established that Ca++ entering the terminal triggers a cascade of events leading to exocytosis, but the details of this cascade are not clear. The model synapse used in the study is the contact formed in culture between avian ciliary ganglion neurons and pectoral myotubes, a cultured neuromuscular junction. Whole cell patch clamp recording methods will be applied to both sides of the synapse, and presynaptic microinjection of specific presynaptic vesicle-associated proteins through the patch pipette will be used to investigate the molecular machinery of neurosecretion. Other useful probes available for this project include antibodies against the vesicular proteins as well as other agents which modulate Ca++-dependent and Ca++-indicating dye. Finally, the presynaptic electrical signs of vesicle fusion with the terminal will also be recorded by analysis of capacitative transients. These results will test the hypotheses that specific proteins (synapsin 1, calcium/calmodulin protein kinase II, calelectrin, synexin) are involved in neurosecretion, the phosphorylations are involved, and that the quantal postsynaptic response is directly related to vesicle fusion.