This application is concerned with combining electrophysiological and ultrastructural techniques in the study of (a) retinal synapses, and (b) cell-to-cell communication in the lens. The first project includes: (1) an analysis of the mechanism of transmitter release and synaptic vesicle membrane recycling in retinal photoreceptors, using rapid freezing at 4 degrees K, freeze-fracturing and ultrastructural tracer techniques; (2) a study of the connectivity of the different functional types of bipolar cells in mammalian retina. Furthermore, (3) the possibility will be explored that functionally active bipolar cell endings could be identified by ultrastructural tracer techniques. The second project is a study of metabolic cooperation in the lens via gap junctions using electron microscopy, intracellular recording technique, tissue culture and biochemistry.