title: Daily rhythms and sex differences in vasoactive intestinal polypeptide, VIPR2 receptor and arginine vasopressin mRNA in the suprachiasmatic nucleus of a diurnal rodent, Arvicanthis niloticus.
abstract: Diurnal and nocturnal animals differ with respect to the time of day at which the ovulatory surge in luteinizing hormone occurs. In some species this is regulated by the suprachiasmatic nucleus (SCN), the primary circadian clock, via cells that contain vasoactive intestinal polypeptide (VIP) and vasopressin (AVP). Here, we evaluated the hypothesis that chronotype differences in the timing of the luteinizing hormone surge are associated with rhythms in expression of the genes that encode these neuropeptides. Diurnal grass rats (Arvicanthis niloticus) were housed in a 12/12-h light-dark cycle and killed at one of six times of day (Zeitgeber time 1, 5, 9, 13, 17, 21; ZT 0 = lights-on). In-situ hybridization was used to compare levels of vip, avp and VIP receptor mRNA (vipr2) in the SCN of intact females, ovariectomized females, ovariectomized females given estradiol and intact males. We found a sex difference in vip rhythms with a peak occurring at ZT 13 in males and ZT 5 in intact females. In all groups avp mRNA rhythms peaked during the day, from ZT 5 to ZT 9, and had a trough in the dark at ZT 21. There was a modest rhythm and sex difference in the pattern of vipr2. Most importantly, the patterns of each of these SCN rhythms relative to the light-dark cycle resembled those seen in nocturnal rodents. Chronotype differences in timing of neuroendocrine events associated with ovulation are thus likely to be generated downstream of the SCN.
authors.affiliation: Veterinary Biosciences, University of Illinois, Urbana, IL, USA. Mmm1@illinois.edu
authors.forename: M M
authors.initials: MM
authors.lastname: Mahoney
authors.forename: C
authors.initials: C
authors.lastname: Ramanathan
authors.forename: M H
authors.initials: MH
authors.lastname: Hagenauer
authors.forename: R C
authors.initials: RC
authors.lastname: Thompson
authors.forename: L
authors.initials: L
authors.lastname: Smale
authors.forename: T
authors.initials: T
authors.lastname: Lee
mesh_terms: D000818:Animals; D001127:Arginine Vasopressin / Q000235:genetics* / Q000378:metabolism; D003411:Arvicolinae; D002940:Circadian Rhythm / Q000235:genetics*; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology; D005260:Female; D005786:Gene Expression Regulation / Q000187:drug effects / Q000502:physiology; D008297:Male; D010052:Ovariectomy / Q000379:methods; D012333:RNA, Messenger / Q000378:metabolism*; D051239:Receptors, Vasoactive Intestinal Peptide, Type II / Q000235:genetics* / Q000378:metabolism; D012727:Sex Characteristics; D012726:Sexual Behavior, Animal / Q000502:physiology; D013493:Suprachiasmatic Nucleus / Q000378:metabolism*
chemical_list: D004967:Estrogens; D012333:RNA, Messenger; D051239:Receptors, Vasoactive Intestinal Peptide, Type II; D001127:Arginine Vasopressin; D004958:Estradiol