title: Influence of stage of the estrous cycle on endogenous opioid modulation of luteinizing hormone, prolactin, and cortisol secretion in the gilt.
abstract: Fourteen gilts that had displayed one or more estrous cycles of 18-22 days (onset of estrus = Day 0) and four ovariectomized (OVX) gilts were treated with naloxone (NAL), an opiate antagonist, at 1 mg/kg body weight in saline i.v. Intact gilts were treated during either the luteal phase (L, Day 10-11; n = 7), early follicular phase (EF, Day 15-17; n = 3), or late follicular phase (LF, Day 18-19; n = 4) of the estrous cycle. Blood was collected at 15-min intervals for 2 h before and 4 h after NAL treatment. Serum luteinizing hormone (LH) concentrations for L gilts averaged 0.65 +/- 0.04 ng/ml during the pretreatment period and increased to an average of 1.3 +/- 0.1 ng/ml (p less than 0.05) during the first 60 min after NAL treatment. Serum prolactin (PRL) concentrations for L gilts averaged 4.8 +/- 0.2 ng/ml during the pretreatment period and increased to an average of 6.3 +/- 0.3 ng/ml (p less than 0.05) during the first 60 min after NAL treatment. Serum PRL concentrations averaged 8.6 +/- 0.7 ng/ml and 7.6 +/- 0.6 ng/ml in EF and LF gilts, respectively, prior to NAL treatment, and decreased (p less than 0.05) to an average of 4.1 +/- 0.2 ng/ml and 5.6 +/- 0.4 ng/ml in EF and LF gilts, respectively, during the fourth h after NAL. Naloxone treatment failed to alter serum LH concentrations in EF, LF, or OVX gilts and PRL concentrations in OVX gilts.(ABSTRACT TRUNCATED AT 250 WORDS)
mesh_terms: D000818:Animals; D004971:Estrus / Q000187:drug effects*; D005260:Female; D006854:Hydrocortisone / Q000097:blood / Q000378:metabolism*; D007700:Kinetics; D007986:Luteinizing Hormone / Q000097:blood / Q000378:metabolism*; D009270:Naloxone / Q000494:pharmacology*; D010052:Ovariectomy; D011388:Prolactin / Q000097:blood / Q000378:metabolism*; D013552:Swine
chemical_list: D009270:Naloxone; D011388:Prolactin; D007986:Luteinizing Hormone; D006854:Hydrocortisone