2008 Eighth Annual Beckman Scholars Symposium
Friday Poster Session - July 28, 2006

While the presence of acetylcholine in the retina is a well known fact, its functional location and effects are a matter of discussion. Acetylcholine is known to be localized in the starburst amacrine cells of the inner retina, but there are various reports confirming or denying its effects in the outer retina, and the downstream receptors in the inner retina are alternately reported to be nicotinic, muscarinic M1/M3 type, muscarinic M2/M4 type, or some combination of the three. Proposals for the function and/or functions of acetylcholine in the retina vary somewhat, but there is some consensus that cholinergic and glycinergic cells form an inhibitory "loop" of signal modulation in the inner retina. Here, we will use molecular and immunocytochemical data to propose a novel addition to that pathway in which M2/M4 receptor activation in the inner retina leads to the activation of neuronal nitric oxide synthase (nNOS), leading to the creation of nitric oxide (NO) which stimulates the downstream effector cGMP in neighboring cells.