N-methyl-d,l-aspartate modulation of pituitary hormone secretion in the pig: role of opioid peptides.
Sixteen ovariectomized (OVX) mature gilts, averaging 139.6 +/- 3.1 kg body weight (BW) were assigned randomly to receive either progesterone (P, 0.85 mg/kg BW, n = 8), or corn oil vehicle (OIL, n = 8) injections im twice daily for 10 d. On the day of experiment, all gilts received either the EAA agonist, N-methyl-d,l-aspartate (NMA; 10 mg/kg BW, iv) alone or NMA plus the EOP antagonist, naloxone (NAL, 1 mg/kg BW, iv), resulting in the following groups of 4 gilts each: OIL-NMA, OIL-NMA-NAL, P-NMA and P-NMA-NAL. Blood samples were collected via jugular cannula every 15 min for 6 hr. All pigs received NMA 5 min following pretreatment with either 0.9% saline or NAL 2 hr after blood collection began and a GnRH challenge 3 hr after NMA. Administration of NMA suppressed (P < 0.03) LH secretion in OIL-NMA gilts and treatment with NAL failed to reverse the suppressive effect of NMA on LH secretion in OIL-NMA-NAL gilts. Similar to OIL-NMA gilts, NMA decreased (P < 0.03) mean serum LH concentrations in P-NMA gilts. However, in P-NMA-NAL gilts, serum LH concentrations were not changed following treatment. All gilts responded to GnRH with increased (P < 0.01) LH secretion. Additionally, administration of NMA increased (P < 0.01) growth hormone (GH) and prolactin (PRL) secretion in both OIL-NMA and P-NMA gilts, but this increase in GH and PRL secretion was attenuated (P < 0.01) by pretreatment with NAL in OIL-NMA-NAL and P-NMA-NAL gilts.(ABSTRACT TRUNCATED AT 250 WORDS)
Chang
W J
WJ
Animal and Dairy Science Department, University of Georgia, Athens, GA 30602.
Barb
C R
CR
Kraeling
R R
RR
Rampacek
G B
GB
Asanovich
K M
KM
D000704:Analysis of Variance; D000818:Animals; D004723:Endorphins / Q000502:physiology*; D005260:Female; D013006:Growth Hormone / Q000378:metabolism; D006854:Hydrocortisone / Q000378:metabolism; D007986:Luteinizing Hormone / Q000378:metabolism; D016202:N-Methylaspartate / Q000494:pharmacology*; D009270:Naloxone / Q000494:pharmacology; D010052:Ovariectomy; D010902:Pituitary Gland / Q000187:drug effects / Q000378:metabolism*; D010907:Pituitary Hormones / Q000378:metabolism*; D011374:Progesterone / Q000494:pharmacology; D011388:Prolactin / Q000378:metabolism; D011863:Radioimmunoassay; D011897:Random Allocation; D013552:Swine / Q000378:metabolism*; D013997:Time Factors
D004723:Endorphins; D010907:Pituitary Hormones; D009270:Naloxone; D011374:Progesterone; D016202:N-Methylaspartate; D011388:Prolactin; D007986:Luteinizing Hormone; D013006:Growth Hormone; D006854:Hydrocortisone