title: Effect of morphine on serum gonadotropin concentrations in postpartum beef cows.
abstract: Morphine (M), an opioid agonist, was administered to postpartum (PP) Angus cows to investigate opioid modulation of gonadotropin secretion. In Exp. 1, eight PP cows (36.9 +/- 2.3 d) received either M (1 mg/kg; n = 4) or saline solution (S) (n = 4) via i.v. injection 36 h after calf removal. Morphine decreased (P less than .01) the number of serum LH pulses (3.0 +/- 1.1 pre- vs .3 +/- .3 post-pulses/h) and, compared with pretreatment values (3.3 mg/ml), decreased (P less than .05) mean LH at 105 min (2.1 ng/ml) through 270 min 1.9 ng/ml +/- .4). Serum prolactin (PRL) increased (P less than .01) following M from 16.4 ng/ml to a peak of 59.3 ng/ml (+/- 3.9). Serum FSH concentrations were unaffected. In Exp. 2, M (.31 mg/kg i.v. injection followed by .15 mg/(kg.h) infusion; n = 6) or S (n = 6) treatments were given for 7 h beginning 36 h after calf removal. Serum LH was similar between groups during the pretreatment and the first 6 h of infusion, but M decreased (P less than .001) the number of serum LH pulses (.44 +/- .09 vs .06 +/- .04 pulses/h). Morphine increased (P less than .05) serum PRL. It is concluded that M differentially modulated gonadotropin secretion in the cow such that PRL increased, LH decreased and FSH was unchanged.
authors.affiliation: University of Georgia, Athens 30602.
authors.forename: D D
authors.initials: DD
authors.lastname: Peck
authors.forename: F N
authors.initials: FN
authors.lastname: Thompson
authors.forename: A
authors.initials: A
authors.lastname: Jernigan
authors.forename: T E
authors.initials: TE
authors.lastname: Kiser
mesh_terms: D000818:Animals; D002417:Cattle / Q000097:blood*; D005260:Female; D006065:Gonadotropins, Pituitary / Q000097:blood*; D009020:Morphine / Q000494:pharmacology*; D049590:Postpartum Period / Q000097:blood* / Q000187:drug effects; D011247:Pregnancy; D011388:Prolactin / Q000097:blood
chemical_list: D006065:Gonadotropins, Pituitary; D009020:Morphine; D011388:Prolactin