Changes in circadian rhythms of thermoregulation and motor activity in rats as a function of aging: effects of d-amphetamine and alpha-MSH.
Thermoregulatory and motor activity circadian cycles are age-dependent. While the level of thermoregulation and motor activity remained almost at the same level during the first 1-15 months during the light portion of the 24-hr cycle, a significant decrease in the level of both rhythms was observed during the dark period. Therefore, older rats exhibited reversed cycles compared with younger rats. Treatments with d-amphetamine resulted in the enhancement of reversal of the cycles. Rats treated with alpha-MSH failed to exhibit a reversal of the cycles. While the effects of d-amphetamine are mediated by the brain DA mesolimbic pathway, it seems that alpha-MSH acts on the dopaminergic system at different sites of action.
D000375:Aging; D000818:Animals; D001831:Body Temperature / Q000187:drug effects; D001833:Body Temperature Regulation / Q000187:drug effects*; D002940:Circadian Rhythm / Q000187:drug effects*; D003624:Darkness; D003913:Dextroamphetamine / Q000494:pharmacology*; D008027:Light; D008297:Male; D009074:Melanocyte-Stimulating Hormones / Q000494:pharmacology*; D009043:Motor Activity / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains
D009074:Melanocyte-Stimulating Hormones; D003913:Dextroamphetamine