title: Effects of melatonin implants in pony mares. 1. Acute effects.
abstract: The effects of melatonin implant treatment over a four week period on LH, estradiol (E2) and progesterone (P4) secretion during the breeding season were studied in ovary-intact and ovariectomized pony mares. Mares with melatonin implants had significantly higher daytime melatonin concentrations than mares with sharm implants (P = 0.0065). In ovariectomized mares, LH secretion did not differ between mares with melatonin and sham implants. In ovary-intact mares, melatonin implants altered the pattern of LH secretion (P = 0.0023) in such a way that an increase in LH secretion was observed during the periovulatory period. Estradiol and P4 secretion were unaffected by melatonin implants. These results suggest that constant administration of melatonin may enhance the secretion of LH during the periovulatory surge but does not adversely affect E2, P4 or basal LH secretion in mares during the breeding season.
authors.affiliation: Department of Animal Science, University of Florida, Gainesville 32611-0701, USA.
authors.forename: M R
authors.initials: MR
authors.lastname: Peltier
authors.forename: G
authors.initials: G
authors.lastname: Robinson
authors.forename: D C
authors.initials: DC
authors.lastname: Sharp
mesh_terms: D000818:Animals; D004343:Drug Implants; D004958:Estradiol / Q000097:blood / Q000378:metabolism; D005260:Female; D006736:Horses / Q000502:physiology*; D016018:Least-Squares Analysis; D016014:Linear Models; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D008550:Melatonin / Q000008:administration & dosage* / Q000097:blood; D008597:Menstrual Cycle / Q000187:drug effects / Q000502:physiology; D010052:Ovariectomy / Q000662:veterinary; D010053:Ovary / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D017440:Photoperiod; D011374:Progesterone / Q000097:blood / Q000378:metabolism; D011863:Radioimmunoassay / Q000662:veterinary; D012044:Regression Analysis; D012588:Scintillation Counting / Q000662:veterinary
chemical_list: D004343:Drug Implants; D011374:Progesterone; D004958:Estradiol; D007986:Luteinizing Hormone; D008550:Melatonin