title: The role of excitatory amino acids in pulsatile secretion of luteinizing hormone in gilts and barrows.
abstract: The relationship of excitatory amino acid (EAA) activity to LH secretion was investigated in ovariectomized crossbred prepuberal gilts (93 +/- 1 kg BW) and Yorkshire barrows (94 +/- 2 kg BW) in two experiments. In Exp. 1, eight gilts received, i.m., saline (S) or 20 mg of Ketamine (K)/kg BW, a noncompetitive EAA receptor antagonist. Within these groups, four then received 10 mg of N-methyl-DL-aspartate (NMA)/kg BW, an EAA agonist, or S i.v. Mean serum LH concentrations were similar among groups before treatment, did not change after S+S, but decreased (P < .05) by 1 h after S+NMA, 3 h after K+S, and 2 h after K+NMA. Serum cortisol concentrations did not change after S+S, but were increased (P < .05) from 30 to 90 min after S+NMA, at 120 min after K+S, and from 30 to 120 min after K+NMA. In Exp. 2, barrows received 2.5 mg of NMA/kg BW i.v. immediately after i.m. injection of S (n = 7) or 19.9 mg of K/kg BW (n = 8). Mean serum LH concentrations for the 2 h before treatment were similar among barrows, but decreased (P < .05) by 2 h after K+NMA and was not altered after S+NMA. Serum cortisol concentrations were increased at 30 min after S+NMA and from 60 to 90 min after K+NMA. We suggest that EAA both inhibit and stimulate LH secretion, with the inhibitory effects lying within the basal hypothalamus and the stimulatory effects lying within higher brain centers.
authors.affiliation: Department of Animal and Dairy Science, University of Georgia, Athens 30602, USA.
authors.forename: J M
authors.initials: JM
authors.lastname: Popwell
authors.forename: M J
authors.initials: MJ
authors.lastname: Estienne
authors.forename: R R
authors.initials: RR
authors.lastname: Kraeling
authors.forename: C R
authors.initials: CR
authors.lastname: Barb
authors.forename: N C
authors.initials: NC
authors.lastname: Whitley
authors.forename: R V
authors.initials: RV
authors.lastname: Utley
authors.forename: G B
authors.initials: GB
authors.lastname: Rampacek
mesh_terms: D000818:Animals; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D018846:Excitatory Amino Acids / Q000502:physiology*; D005260:Female; D006854:Hydrocortisone / Q000097:blood; D007649:Ketamine / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood*; D008297:Male; D016202:N-Methylaspartate / Q000494:pharmacology; D010052:Ovariectomy / Q000662:veterinary; D010913:Pituitary-Adrenal System / Q000187:drug effects / Q000502:physiology; D013552:Swine / Q000097:blood* / Q000502:physiology
chemical_list: D018690:Excitatory Amino Acid Agonists; D018691:Excitatory Amino Acid Antagonists; D018846:Excitatory Amino Acids; D016202:N-Methylaspartate; D007649:Ketamine; D007986:Luteinizing Hormone; D006854:Hydrocortisone