title: Neuroendocrine changes in male hamsters following photostimulation.
abstract: Transfer of gonadally regressed male golden hamsters from a short (5 L:19 D) to a stimulatory (14 L:10 D) photoperiod elicits, within 24 hr, significant changes in hypothalamic dopamine, serotonin, and possibly norepinephrine metabolism. Hypothalamic LHRH content was significantly elevated in short-photoperiod animals, but within 24 hr of transfer to a 14:10 photoperiod, LHRH declined to levels not different from those in hamsters maintained continuously in a long photoperiod. Plasma FSH levels were also significantly elevated within 24 hr of transfer, but increases in plasma LH were somewhat slower. Chronic treatment with the tyrosine hydroxylase inhibitor, alpha-methyl tyrosine (alpha MPT), which inhibits catecholamine synthesis, blocked the effect of a stimulatory photoperiod on plasma FSH levels, while treatment of 5:19 hamsters with the catecholamine precursor, L-dopa, mimicked the effects of photostimulation on plasma FSH levels. Testicular weights were not affected by alpha MPT or L-dopa treatment for 1 week. From these data, it appears that endocrine events associated with photoperiod-induced testicular recrudescence are under the control of hypothalamic neurotransmitters.
mesh_terms: D000818:Animals; D006224:Cricetinae; D004298:Dopamine / Q000032:analysis / Q000378:metabolism*; D005640:Follicle Stimulating Hormone / Q000097:blood; D007987:Gonadotropin-Releasing Hormone / Q000032:analysis; D006897:Hydroxyindoleacetic Acid / Q000032:analysis / Q000378:metabolism; D007031:Hypothalamus / Q000032:analysis / Q000502:physiology*; D007980:Levodopa / Q000494:pharmacology; D008027:Light; D007986:Luteinizing Hormone / Q000097:blood; D008297:Male; D008647:Mesocricetus; D008781:Methyltyrosines / Q000494:pharmacology; D009638:Norepinephrine / Q000032:analysis / Q000378:metabolism*; D010507:Periodicity; D011388:Prolactin / Q000097:blood; D012669:Seminal Vesicles / Q000032:analysis; D012701:Serotonin / Q000032:analysis / Q000378:metabolism*; D013737:Testis / Q000032:analysis; D019805:alpha-Methyltyrosine
chemical_list: D008781:Methyltyrosines; D012701:Serotonin; D007987:Gonadotropin-Releasing Hormone; D007980:Levodopa; D006897:Hydroxyindoleacetic Acid; D019805:alpha-Methyltyrosine; D011388:Prolactin; D007986:Luteinizing Hormone; D005640:Follicle Stimulating Hormone; D004298:Dopamine; D009638:Norepinephrine