Behavioral effects of [4-norleucine, 7-D-phenylalanine]-alpha-melanocyte-stimulating hormone.
The behavioral effects of alpha-melanocyte stimulating hormone (alpha-MSH) were compared to an alpha-MSH analogue that had a norleucine substituted for methionine in the four position and a D-phenylalanine substituted for L-phenylalanine in the seven position. [Nle4, D-Phe7]-alpha-MSH has previously been shown to be a superpotent agonist on melanocytes [17]. The present experiments indicate that [Nle4, D-Phe7]-alpha-MSH is equipotent to alpha-MSH in inducing grooming when administered intraventricularly. In contrast, the analogue has the opposite effect of alpha-MSH on performance of a visual discrimination task. alpha-MSH improves visual performance whereas [Nle4, D-Phe7]-alpha-MSH attenuates such performance. The contrasting activities of [Nle4, D-Phe7]-alpha-MSH on the physiological processes described suggest that this analogue may interact with three distinct melanotropin receptors in different ways. On melanocyte receptors the melanotropin analogue is a superagonist, on CNS melanotropin receptors involved in grooming it is equipotent to alpha-MSH, and on CNS receptors involved in attention, learning and memory [Nle4, D-Phe7]-alpha-MSH may be an antagonist of endogenous melanotropin.
D000818:Animals; D004193:Discrimination Learning / Q000187:drug effects*; D005108:Extinction, Psychological / Q000187:drug effects; D006120:Grooming / Q000187:drug effects*; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000031:analogs & derivatives* / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D012054:Reinforcement, Psychology; D012193:Reversal Learning / Q000187:drug effects; D000521:alpha-MSH / Q000031:analogs & derivatives*
D000521:alpha-MSH; C027756:MSH, 4-Nle-7-Phe-alpha-; D009074:Melanocyte-Stimulating Hormones