The long term objective is to characterize the morphological and biochemical diversity of retinal ganglion cells (RGCs) and to determine the central projections of individual types of ganglion cells. About 20 percent of RGCs synthesize nicotinic acetylcholine receptors (nAChRs) and transport them to their axon terminals. It is proposed to study these RGC populations and examine the function of these transported receptors. The immediate specific aims include: (1) to characterize these RGCs containing nAChRs, including morphology, neurotransmitter receptor counts and their central projections; (2) to identify the source of cholinergic inputs that may act upon these RGC axonal terminals; (3) to determine if ACh-containing dendrites and/or axons form synapses upon retinal axons; (4) to determine if ganglion cell axonal nAChRs in tectum are functional and whether cholinergic agonists modify properties of retinal axonal terminals; (5) to determine the temporal pattern of innervation of axon-containing nAChRs into the tectum and ventral geniculate during development; and (6) to determine when during ontogeny nAChRs in RGCs become functional. These studies will help in determining the role of nicotine in visual function in the retina and the brain during embryogenesis and responses of RGCs to injury.
