alpha-MSH- and novelty-induced emotional responses in rats: associated changes in plasma corticosterone and brain catecholamines.
In a series of experiments it was demonstrated that defecation responses induced in rats by exposure to novel environments did not habituate if the animals were treated with alpha-melanocyte stimulating hormone (alpha-MSH). The MSH-treated rats sustained high defecation responses on 6 successive days of exposure, whereas control rats habituated. The role of plasma 11-hydroxycorticosterone (11-OHCS) levels and brain catecholamines (CAs) in this novelty-induced defecation following alpha-MSH administration was also investigated. Baseline studies showed that MSH treatment alone increased plasma 11-OHCS levels in the resting condition and lowered brain dopamine (DA) but not norepinephrine (NE) concentrations. It was found, however, that plasma 11-OHCS levels in MSH-treated rats were not significantly increased on successive days of combined MSH and novelty treatments but that whole brain DA and NE concentrations were both lowered. A strong negative correlation was observed between defecation responses and brain DA concentrations on successive days of the joint MSH and novelty treatment. In all the experiments alpha-MSH treatment had no effect on step-down activity.
D015062:11-Hydroxycorticosteroids / Q000097:blood*; D000818:Animals; D001921:Brain / Q000187:drug effects / Q000378:metabolism*; D004298:Dopamine / Q000378:metabolism*; D004644:Emotions / Q000187:drug effects*; D006185:Habituation, Psychophysiologic / Q000187:drug effects; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism*; D051381:Rats; D012931:Social Environment
D015062:11-Hydroxycorticosteroids; D009074:Melanocyte-Stimulating Hormones; D004298:Dopamine; D009638:Norepinephrine