Reproductive suppression in subordinate female highveld mole-rats (Cryptomys hottentotus pretoriae): no role for endogenous opioid peptides.
The influence of endogenous opioid peptides (EOPs) on plasma luteinizing hormone (LH) levels in subordinate female highveld mole-rats (Cryptomys hottentotus pretoriae) was investigated to elucidate the physiological mechanisms responsible for inhibiting their gonadotropin-releasing hormone (GnRH) and/or LH release. The opioid antagonist naloxone was administered either alone or with GnRH. A single injection of naloxone failed to alter plasma LH levels in dominant reproductive females or in subordinate non-reproductive females in the presence or absence of their ovaries. Pituitary sensitivity to a GnRH challenge was not influenced by naloxone administered acutely or according to longer-term regimens in any of the treatment groups. The results suggest no role for EOPs at the level of the pituitary or hypothalamus in the socially induced infertility evident in non-reproductive female highveld mole-rats.
Mammal Research Institute, Department of Zoology and Entomology, University of Pretoria, Pretoria 0002, South Africa.
Lydia
L
Du Toit
Nigel C
NC
Bennett
Gundula H
GH
Gutjahr
Clive W
CW
Coen
D000704:Analysis of Variance; D000818:Animals; D001522:Behavior, Animal; D004291:Dominance-Subordination; D004338:Drug Combinations; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000097:blood / Q000494:pharmacology; D007986:Luteinizing Hormone / Q000097:blood; D019577:Mole Rats / Q000378:metabolism; D009270:Naloxone / Q000494:pharmacology; D009292:Narcotic Antagonists / Q000494:pharmacology; D018847:Opioid Peptides / Q000378:metabolism*; D011863:Radioimmunoassay / Q000379:methods; D012098:Reproduction / Q000187:drug effects / Q000502:physiology*; D013997:Time Factors
D004338:Drug Combinations; D009292:Narcotic Antagonists; D018847:Opioid Peptides; D007987:Gonadotropin-Releasing Hormone; D009270:Naloxone; D007986:Luteinizing Hormone