Comparison of biological and behavioral activities of alpha- and gamma-melanocyte stimulating hormones.
The biological and behavioral activities of gamma-MSH (gamma-MSH) and alpha-MSH (alpha-MSH) were compared using three different tests: darkening of the skin of Anolis, grooming behavior of rats, and performance of a visual discrimination task by rats. When incubated with the Anolis skin, both peptides cause skin darkening. However, alpha-MSH is much more potent than gamma-MSH. The alpha-MSH effect is not antagonized by coincubation with gamma-MSH. When given intraventricularly to rats, alpha-MSH induces a marked grooming behavior. This effect was not noted upon administration of gamma-MSH. Injection of gamma-MSH with the alpha-MSH did not produce a grooming response significantly different from alpha-MSH alone. In the visual discrimination task, the two peptides had opposite effects on the rate at which rats learned the initial discrimination and a subsequent reversal. The peptides were injected intraperitoneally prior to behavioral testing. Following alpha-MSH, rats learned the discrimination and subsequent reversal faster than the control rats. Following gamma-MSH, rats learned the initial discrimination at approximately the same rate as controls, and learned the reversal much slower. These results are discussed in terms of the similarity and differences in the mechanisms of action of alpha-MSH and gamma-MSH.
D000818:Animals; D001522:Behavior, Animal / Q000187:drug effects*; D004193:Discrimination Learning / Q000187:drug effects; D008116:Lizards; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology; D051381:Rats; D012867:Skin / Q000187:drug effects; D012879:Skin Physiological Phenomena; D014796:Visual Perception / Q000187:drug effects
D009074:Melanocyte-Stimulating Hormones