The objective of this research proposal is to study the basic mechanism of the excitation-transmitter release coupling process at the presynaptic terminal and associated postsynaptic electrogenesis in the chemical synapse at the molecular level. The selected preparations are the squid giant synapse and the nerve-electroplaque synapse of weakly electric fish (e.g., Eigenmannia). In the squid giant synapse we will continue to study on the role of Ca 2 ion by employing aequorin and voltage clamp techniques. In the Eigenmannia electroplaque synapse, which is presumably cholinergic, we will study the physiological mechanism of high frequency (over 500 Hz at 30 degrees C) synaptic transmission without fatigue. To achieve this goal, we will combine electrophysiological, neurochemical and electronmicroscopical techniques.