Abstract
Previous studies have shown muscarinic receptors are involved in light driven
pigment dispersion in retinal pigment epithelia (RPE). Pharmacological agents can be
used to test this hypothesis and by selective inhibition, elucidate the sub-class of the
receptor involved, and the intracellular downstream signaling pathway. RPE was isolated
from Lepomis macrochirus, commonly known as bluegill, and treated with various
pharmacological agents, including muscarinic receptor antagonists and agents to block
second messenger pathway targets. Telenzepine and p-FHHSiD, M1 and M3 receptor
antagonists, respectively, blocked pigment granule dispersion induced by carbachol,
while methoctramine, an M2 antagonist did not. U73122 and 2-APB, a phospholipase C
inhibitor and IP3-receptor antagonist, respectively, were also able to block carbachol-induce dispersion. Therefore, I conclude that carbachol-induced pigment dispersion 1s
mediated through Motltl receptors. I also propose that Ca2+ could be necessary for
pigment dispersion mduced by carbachol.
