Role of the M-1 receptor in regulating circadian rhythms

Cholinergic stimuli are potent regulators of the circadian clock in the hyp othalamic suprachiasmatic nucleus (SCN). Using a brain slice model, we have found that the SCN clock is subject to muscarinic regulation, a sensitivit y expressed only during the night of the clock's 24-h cycle. Pharmacologica l and signal transduction characteristics are compatible with a response me diated by an M-1-like receptor. Molecular manipulation of muscarinic recept ors will provide important insights as to the receptor subtype(s) regulatin g circadian rhythms. (C) 2001 Elsevier Science Inc. All rights reserved.