At the back of the eye is the retina, which includes the retinal pigment epithelium (RPE) as well as photoreceptor cells. The cells of the pigment epithelium in many vertebrates contain a dark pigment that screens light, and this pigment can shuttle out into finger-like projections of the RPE cells htat in turn interdigitate with the photoreceptors. In teleost fish, when the eye is in bright conditions, pigment granule dispersion is an important component of retinal responses associated with light adaptation. It is not fully clear how a light signal to the photoreceptors triggers the RPE to control this pigment dispersion. One extracellular messenger is known to be the amino acid dopamine, and recent data show that the compound carbachol also induces pigment granule dispersion in teleost fish RPE. Because carbachol mimics the effects of the neurotransmitter acetylcholine, the discovery of carbachol's effects suggests a role for acetylcholine as a physiological messenger molecule signaling bright light conditions to the RPE. Acetylcholine and carbachol act on target cells by binding to a class of molecular receptors called muscarinic receptors. This project uses molecular techniques and information currently available from zebrafish genome projects to test whether bluegill fish have genes to express particular types of muscarinic receptors, and whether these receptors are responsible for the carbachol-induced dispersion. Results will establish how acetylcholine might act as an extracellular messenger in the teleost eye RPE, and will have an impact beyond sensory neurobiology by advancing our understanding of the biology of muscarinic receptors and cholinergic signaling. This Research at Undergraduate Institutions (RUI) project also provides an excellent opportunity for undergraduate training, in particular including students from historically underserved minority groups, with a minority woman faculty PI as a role model.
