title: Activation of M1/4 receptors phase advances the hamster circadian clock during the day.
abstract: The mammalian circadian clock in the suprachiasmatic nucleus (SCN) can be reset by the cholinergic agonist carbachol. In hamsters, intraSCN carbachol produces phase advances during the day. This phenomenon has previously been attributed to the muscarinic receptors, as carbachol-induced phase shifts are blocked by pretreatment with the muscarinic antagonist atropine. The SCN contains all five muscarinic receptors, leaving open the question as to which muscarinic receptors mediate these shifts. Here we test two selective muscarinic agonists, the M1/4 agonist McN-A-343 and the M2/3 agonist bethanechol, in addition to the non-selective cholinergic agonist carbachol. Consistent with previous reports, carbachol produced significant phase advances when injected to the SCN during the mid-subjective day. At the doses used here, McN-A-343, but not bethanechol, also produced significant phase shifts when injected to the SCN during the mid-subjective day. Phase shifts to McN-A-343 were as large as those produced by carbachol, suggesting that activation of the M1/4 receptors alone can fully account for the daytime phase advances produced by cholinergic agonists. Given acetylcholine's role in arousal, and the similarity between phase advances to carbachol/McN-A-343 and to exercise and arousal manipulations, it is possible that acetylcholine may contribute to non-photic resetting of the circadian clock.
authors.affiliation: Department of Psychology, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada; Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Dr. NW, Calgary, AB T2N 4N1, Canada.
authors.forename: Priyoneel
authors.initials: P
authors.lastname: Basu
authors.affiliation: Department of Psychology, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada; Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Dr. NW, Calgary, AB T2N 4N1, Canada.
authors.forename: Adrienne L
authors.initials: AL
authors.lastname: Wensel
authors.affiliation: Department of Psychology, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada; Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Dr. NW, Calgary, AB T2N 4N1, Canada.
authors.forename: Reid
authors.initials: R
authors.lastname: McKibbon
authors.affiliation: Department of Psychology, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada; Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Dr. NW, Calgary, AB T2N 4N1, Canada.
authors.forename: Nicole
authors.initials: N
authors.lastname: Lefebvre
authors.affiliation: Department of Psychology, University of Calgary, 2500 University Dr. NW, Calgary, AB T2N 1N4, Canada; Hotchkiss Brain Institute, University of Calgary, 3330 Hospital Dr. NW, Calgary, AB T2N 4N1, Canada; Department of Physiology and Pharmacology, University of Calgary, 3330 Hospital Dr. NW, Calgary, AB T2N 4N1, Canada. Electronic address: michael.antle@ucalgary.ca.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Antle
mesh_terms: D008455:(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride / Q000494:pharmacology; D000818:Animals; D018723:Bethanechol / Q000494:pharmacology; D002217:Carbachol / Q000494:pharmacology; D018679:Cholinergic Agonists / Q000494:pharmacology; D057906:Circadian Clocks / Q000187:drug effects; D008297:Male; D008647:Mesocricetus; D043643:Receptor, Muscarinic M1 / Q000819:agonists*; D043585:Receptor, Muscarinic M2 / Q000819:agonists; D043587:Receptor, Muscarinic M3 / Q000819:agonists; D043588:Receptor, Muscarinic M4 / Q000819:agonists*; D013493:Suprachiasmatic Nucleus / Q000187:drug effects / Q000502:physiology
chemical_list: D018679:Cholinergic Agonists; D043643:Receptor, Muscarinic M1; D043585:Receptor, Muscarinic M2; D043587:Receptor, Muscarinic M3; D043588:Receptor, Muscarinic M4; D018723:Bethanechol; D008455:(4-(m-Chlorophenylcarbamoyloxy)-2-butynyl)trimethylammonium Chloride; D002217:Carbachol
keywords: Acetylcholine; Circadian; Muscarinic; Non-photic; Suprachiasmatic nucleus