title: Effects of lighting condition on circadian behavior in 5-HT1A receptor knockout mice.
abstract: Serotonin (5-HT) is an important regulator of the mammalian circadian system, and has been implicated in modulating entrained and free-running rhythms, as well as photic and non-photic phase shifting. In general, 5-HT appears to oppose the actions of light on the circadian system of nocturnal rodents. As well, 5-HT mediates, at least in part, some non-photic responses. The 5-HT1A, 1B and 7 receptors regulate these acute responses to zeitgebers. 5-HT also regulates some entrained and free-running properties of the circadian clock. The receptors that contribute to these phenomena have not been fully examined. Here, we use 5-HT1A receptor knockout (KO) mice to examine the response of the mouse circadian system to a variety of lighting conditions, including a normal light-dark cycle (LD), T-cycles, phase advanced LD cycles, constant darkness (DD), constant light (LL) and a 6 hour dark pulse starting at CT5. Relative to wildtype mice, the 5-HT1A receptor KO mice have lower levels of activity during the first 8h of the night/subjective night in LD and LL, later activity onsets on transient days during re-entrainment, shorter free-running periods in LL when housed with wheels, and smaller phase shifts to dark pulses. No differences were noted in activity levels during DD, alpha under any light condition, free-running period in DD, or phase angle of entrainment in LD. While the 5-HT1A receptor plays an important role in regulating photic and non-photic phase shifting, its contribution to entrained and free-running properties of the circadian clock is relatively minor.
authors.affiliation: Department of Psychology, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Victoria M
authors.initials: VM
authors.lastname: Smith
authors.affiliation: Department of Psychology, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Ryan T
authors.initials: RT
authors.lastname: Jeffers
authors.affiliation: Department of Psychology, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Brendan B
authors.initials: BB
authors.lastname: McAllister
authors.affiliation: Department of Psychology, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Priyoneel
authors.initials: P
authors.lastname: Basu
authors.affiliation: Department of Psychology, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada; Department of Cell Biology and Anatomy, University of Calgary, Calgary, Alberta, Canada.
authors.forename: Richard H
authors.initials: RH
authors.lastname: Dyck
authors.affiliation: Department of Psychology, University of Calgary, Calgary, Alberta, Canada; Hotchkiss Brain Institute, University of Calgary, Calgary, Alberta, Canada; Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta, Canada. Electronic address: antlem@ucalgary.ca.
authors.forename: Michael C
authors.initials: MC
authors.lastname: Antle
mesh_terms: D000221:Adaptation, Ocular / Q000235:genetics*; D000818:Animals; D002940:Circadian Rhythm / Q000235:genetics*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009043:Motor Activity / Q000235:genetics; D010775:Photic Stimulation; D044282:Receptor, Serotonin, 5-HT1A / Q000172:deficiency*; D012701:Serotonin / Q000378:metabolism; D013997:Time Factors
chemical_list: D044282:Receptor, Serotonin, 5-HT1A; D012701:Serotonin
keywords: 5-HT(1A); Amplitude; Behavior; Circadian; Dark pulse; Mice; Period; Serotonin