Carbachol-Induced Pigment Granule Dispersion

The retinal pigment epithelium (RPE) is a monolayer of pigmented, simple cuboidal epithelium with long apical processes that interdigitate with photoreceptors. In teleosts, the RPE aids in light adaptation through pigment granule movements. In the bright light, pigment granules are dispersed into the long apical processes thereby shielding rods from excessive light. The opposite occurs in dark conditions; pigment granules are aggregated into the cell body of the RPE allowing the maximal exposure of the rods to incoming light. Using isolated bluegill (Lepomis macrochirus) RPE, I examined the effects that carbachol and acetylcholine analog, has on pigment granule dispersion in a dose-dependent manner, and the maximum effects of carbachol were observed at concentrations as low as 10 nM. Atropine was highly effective in blocking carbachol-induced dispersion. The role of specific muscarinic receptor subtypes (Ml-M3) in mediating carbachol-induced dispersion was investigated. The M1 and M3 blockers pirenzepine and 4-DAMP, respectively, were effective in blocking carbachol-induced dispersion. The M2 antagonist, AFDX-116, did not block carbachol-induced dispersion. Consistent with these results, the M1 agonist, 4-chlorophenyl stimulated pigment granule dispersion, while arecaidine, an M2 agonist, did not. I conclude that carbachol-induced pigment granule dispersion is mediated via M1 and M3 but not M2 subtypes of the muscarinic receptor family.

Name thesis:degree_name

Master of Science

Level thesis:degree_level

Masters

Discipline thesis:degree_discipline

Biology

Grantor

Southwest Texas State University

Year dc:date.issued

2000

Author dc:creator

• Gonzalez, Alfredo

Advisor dc:contributor.advisor

• Garcia, Dana

Committee members dc:contributor.committeemember

• Koke, Joseph
• Ott, Jim

• rhodopsin
• bluegill
• epithelium
• muscarinic receptors
• dispersion

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10877/13208

OAI identifier oai:identifier

oai:digital.library.txst.edu:10877/13208