title: Serotonin1A-mediated amplification of light-induced phase advances of circadian rhythms in the Syrian hamster: post-light effects.
abstract: Certain serotonergic compounds that have an agonist/antagonist activity at the 5-HT(1A) receptor subtype are known to greatly potentiate the ability of light to advance the phase of circadian activity rhythms in hamsters. Typically, investigational compounds are injected 30 min to 1 h prior to a phase-advancing light pulse, and it is not known if these compounds are efficacious when injected after a short light pulse. In this study we injected the 5-HT(1A) mixed agonist/antagonist BMY 7378 from 1 to 7 h after a short phase advancing light pulse at CT 19 in hamsters to assess the temporal window of efficacy of this compound. BMY 7378 effectively doubles the magnitude of light-induced phase advances in hamster circadian wheel running rhythms for 6 h after a light pulse administered at CT 19, and this effect abruptly ends at 7 h post-light. This demonstrates that the molecular events initiated by a light pulse at CT 19 responsible for initiating phase advances in circadian activity rhythms can be modulated for at least the next 6 h in the hamster. However, this effect found with BMY 7378 does not extend to all serotonergic compounds as the inhibitory activity of 8-OH-DPAT on light-induced phase advances is not apparent when injected just 3 h after a light pulse. Since BMY 7378 can elicit such major shifts in the timing of the circadian clock it should be useful as a tool to explore potential changes in gene expression that lead to phase shifts in circadian rhythms, now known to be susceptible to modification for 6 h after a phase-advancing light pulse.
authors.affiliation: Department of Biology, Valdosta State University, Valdosta, GA 31698, USA.
authors.forename: Elizabeth
authors.initials: E
authors.lastname: Lungwitz
authors.forename: Robert L
authors.initials: RL
authors.lastname: Gannon
mesh_terms: D017371:8-Hydroxy-2-(di-n-propylamino)tetralin / Q000008:administration & dosage / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002940:Circadian Rhythm / Q000187:drug effects; D006224:Cricetinae; D008027:Light; D008647:Mesocricetus; D009043:Motor Activity / Q000187:drug effects / Q000502:physiology; D010879:Piperazines / Q000008:administration & dosage / Q000494:pharmacology*; D044282:Receptor, Serotonin, 5-HT1A / Q000378:metabolism*; D058825:Serotonin 5-HT1 Receptor Agonists; D058829:Serotonin 5-HT1 Receptor Antagonists
chemical_list: D010879:Piperazines; D058825:Serotonin 5-HT1 Receptor Agonists; D058829:Serotonin 5-HT1 Receptor Antagonists; D044282:Receptor, Serotonin, 5-HT1A; D017371:8-Hydroxy-2-(di-n-propylamino)tetralin; C053428:BMY 7378