title: Photoperiodic changes in opiate binding and their functional implications in golden hamsters.
abstract: Daylength modulates gonadotropin secretion, gonadal steroid hormone feedback, sexual behavior and body weight in male golden hamsters. Endogenous opiates regulate each of these phenomena, and the ability of opiate receptor blockade to elevate serum LH secretion is photoperiod-dependent. We used in vitro autoradiography to localize and quantify effects of daylength in golden hamsters. Hamsters were exposed to stimulatory (14 h light: 10 h dark) or inhibitory (10 h light: 14 h dark) photoperiods for 10 weeks before specific [3H]naloxone binding was assessed. Short days significantly decreased binding in medial amygdala and the intercalated amygdaloid nucleus. This effect was reversed by superior cervical ganglionectomy. No significant effects of daylength were observed in other amygdaloid, hypothalamic or preoptic areas. Lesions of the medial amygdala decreased copulatory behavior, short day-induced weight loss, and anogenital chemoinvestigation but did not affect gonadal regression or other forms of chemoinvestigation. These lesions facilitated testosterone's negative feedback on luteinizing hormone in long days but did not interfere with the potentiation of negative feedback by short days.
authors.affiliation: Department of Zoology, University of Massachusetts, Amherst 01003.
authors.forename: M L
authors.initials: ML
authors.lastname: Tubbiola
authors.forename: B
authors.initials: B
authors.lastname: Nock
authors.forename: E L
authors.initials: EL
authors.lastname: Bittman
mesh_terms: D000818:Animals; D002940:Circadian Rhythm; D006224:Cricetinae / Q000502:physiology*; D004723:Endorphins / Q000378:metabolism / Q000502:physiology*; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D008647:Mesocricetus / Q000378:metabolism / Q000502:physiology*; D009270:Naloxone / Q000378:metabolism*; D009929:Organ Size; D012726:Sexual Behavior, Animal / Q000502:physiology*; D013739:Testosterone / Q000097:blood
chemical_list: D004723:Endorphins; D009270:Naloxone; D013739:Testosterone; D007986:Luteinizing Hormone