title: Effect of naloxone treatment on luteinizing hormone and testosterone concentrations in boars with high and low libido.
abstract: The objective was to determine the effects of the opioid peptide receptor antagonist, naloxone on circulating concentrations of luteinizing hormone (LH) and testosterone in boars characterized as having high (n=8) or low libido (n=8) based on the willingness to mount an artificial sow and allow semen collection. On the day of the experiment, blood was sampled every 15 min for 4 h before and 4 h after i.v. injection of naloxone (1 mg/kg body weight). After naloxone treatment, a libido status by time interaction was detected and concentrations of LH within 15 min after treatment were greater (p<0.05) for High-libido boars than for Low-libido boars. Concentrations of testosterone were highly variable amongst boars and there were no effects of libido status (p=0.66) or libido status by time (p=0.66). There was, however, an effect of time (p<or=0.01), and concentrations of testosterone in samples collected between 0.5 and 1.25 h after naloxone were greater than concentrations in samples collected prior to injection. In summary, the responsiveness of the hypothalamic-gonadotropic-gonadal axis to opioid receptor antagonism was heightened in boars displaying a high level of sexual motivation.
authors.affiliation: Department of Animal and Poultry Sciences, Virginia Polytechnic Institute and State Uniersity, Blacksburg, VA, USA. mestienn@vt.edu
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Estienne
authors.forename: Allen F
authors.initials: AF
authors.lastname: Harper
authors.forename: Susan M
authors.initials: SM
authors.lastname: Speight
authors.forename: Russell J
authors.initials: RJ
authors.lastname: Crawford
authors.forename: C Richard
authors.initials: CR
authors.lastname: Barb
mesh_terms: D000818:Animals; D007031:Hypothalamus / Q000502:physiology; D007989:Libido; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D018847:Opioid Peptides / Q000502:physiology*; D012726:Sexual Behavior, Animal / Q000187:drug effects / Q000502:physiology; D034421:Sus scrofa; D013737:Testis / Q000502:physiology; D013739:Testosterone / Q000097:blood*
chemical_list: D009292:Narcotic Antagonists; D018847:Opioid Peptides; D009270:Naloxone; D013739:Testosterone; D007986:Luteinizing Hormone