Intraventricular carbachol mimics the effects of light on the circadian rhythm in the rat pineal gland.
Environmental lighting regulates numerous circadian rhythms, including the cycle in pineal serotonin N-acetyltransferase activity. Brief exposure of rats to light can shift the phase of this enzyme's circadian rhythm. Light also rapidly reduces nocturnal enzyme activity. Intraventricular injections of carbachol, a cholinergic agonist, can mimic both of these effects. Light and carbachol presumably act on the suprachiasmatic nucleus of the hypothalamus. These experiments demonstrate the feasibility of using a neuropharmacologic approach to the mechanisms underlying mammalian circadian rhythms.
D000123:Acetyltransferases / Q000378:metabolism; D000818:Animals; D001683:Biological Clocks / Q000187:drug effects; D002217:Carbachol / Q000008:administration & dosage / Q000494:pharmacology*; D002940:Circadian Rhythm / Q000187:drug effects* / Q000528:radiation effects; D007276:Injections, Intraventricular; D008027:Light; D008297:Male; D018377:Neurotransmitter Agents / Q000494:pharmacology; D010870:Pineal Gland / Q000201:enzymology / Q000502:physiology*; D051381:Rats; D012701:Serotonin
D018377:Neurotransmitter Agents; D012701:Serotonin; D002217:Carbachol; D000123:Acetyltransferases