Spontaneous waves of excitation, which occur in the developing retina during a specific time period immediately before the onset of vision, are believed to provide important cues for the development of precise neuronal connectivity in the visual system. However, the mechanisms underlying the formation and regulation of these retinal waves are unknown. Studies proposed in this competing renewal application will investigate neuronal interactions important for the generation, propagation, and regulation of spontaneous waves in the developing retina, with an emphasis on neurotransmitter-mediated interactions in starburst amacrine and ganglion cells. Through a set of carefully selected specific aims, these studies will test several critical and specific aspects of the general hypothesis that spontaneous waves in the mammalian retina are mediated, to a large extent, by multiple neurotransmitter systems interacting in a highly coordinated and age-dependent manner. These specific aims aim to: (1) identify the contribution of the developing cholinergic, glutamatergic, glycinergic, and GABAergic systems to the formation of spontaneous neuronal activity at various stages of retinal development; (2) understand the rhythmicity and temporal regulation of spontaneous retinal waves; and (3) identify the interrelationship among wave dynamics, neuronal activity, and transmitter interaction. To achieve the above aims, cellular physiological and pharmacological experiments have been designed to take advantage of a unique whole-mount retinal preparation, which allows the integration of a number of cutting-edge neurophysiological techniques, including simultaneous Ca2+ imaging and patch-clamp recording, dual patch-clamp recording from identified cell pairs, and particle-delivered fluorescent labeling of living retinal neurons. This comprehensive approach will enable the investigators to obtain, at the synaptic, cellular, and network levels, critical data on retinal waves previously unattainable in other experimental settings. Results from these studies are expected to provide much needed information about neuronal interaction and spontaneous excitation in the developing retina, thus allowing better understanding of visual development and retinal processing in healthy and diseased states.