alpha-MSH, MIF-I and melatonin: effects on novelty-induced defecation, plasma 11-OHCS and central catecholamines in rats.
The pituitary-hypothalamo-pineal complex involving MSH, MIF-I and melatonin has been strongly emphasized in the adaptive mechanism of the animal. A series of experiments was conducted to investigate the effects of alpha-MSH, MIF-I and melatonin on novelty-induced defecation, step-down activity, plasma 11-OHCS levels and whole brain DA and NE concentrations over days of novelty X drug treatment. alpha-MSH consistently enhanced and sustained novelty-induced defecation, increased plasma 11-OHCS levels in the resting intact rats and in the novelty exposed hypophysectomized (hypox) rats, and decreased brain DA and NE levels in intact, hypox and sham-hypox rats. MSH did not increase plasma 11-OHCS in intact and sham-hypox rats during exposure to novelty. MIF-I significantly habituated novelty-induced defecation and increased brain DA and NE levels over 5 days of drug X novelty treatment. Melatonin, on the other hand, inhibited novelty-induced defecation, decreased plasma 11-OHCS and increased brain DA level over 5 days of melatonin X novelty treatment. MSH, MIF-I or melatonin did not show any significant effect on the step-down activity of the rats. The results suggest the possibility that central CAs may be implicated in the behavioral changes observed after alpha-MSH, MIF-I and melatonin administration and in the interaction of the pituitary-hypothalamo-pineal complex involving MSH, MIF-I and melatonin.
D015062:11-Hydroxycorticosteroids / Q000097:blood*; D000818:Animals; D001923:Brain Chemistry / Q000187:drug effects*; D002395:Catecholamines / Q000378:metabolism*; D003672:Defecation / Q000187:drug effects*; D004777:Environment; D007016:Hypophysectomy; D009075:MSH Release-Inhibiting Hormone / Q000494:pharmacology*; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology*; D008550:Melatonin / Q000494:pharmacology*; D051381:Rats
D015062:11-Hydroxycorticosteroids; D002395:Catecholamines; D009074:Melanocyte-Stimulating Hormones; D009075:MSH Release-Inhibiting Hormone; D008550:Melatonin