Age- and sex-specific changes in naloxone-induced luteinizing hormone secretion and Fos expression in gonadotropin-releasing hormone neurons of gonadectomized rats.
In the present study, we examined sex-specific changes in luteinizing hormone (LH) secretion and Fos expression in gonadotropin-releasing hormone (GnRH) neurons in response to naloxone in young (3 months old) and old (24 months old), gonadectomized male and female rats. We revealed by immunocytochemistry that, regardless of age and sex, naloxone significantly increased the number of GnRH neurons expressing Fos, which was associated with increased LH secretion. Additionally, although the magnitude of the increase in Fos-expressing GnRH neurons did not change in old males compared to young males, it was attenuated by almost half in old females compared to young females. LH levels decreased 60% in old males compared to young males and 15% in old females compared to young females. These results suggest LH secretion is impaired with age, but the ability of GnRH neurons to be stimulated by naloxone is preserved. However, the opioid-controlling mechanism is more fragile in females than males during aging.
Funabashi
Toahiya
T
Department of Physiology, Yokohama City University Graduate School of Medicine, 3-9 Fukuura, Kanazawa-ku, Yokohama 236-0004, Japan. toshiya@med.yokohama-cu.ac.jp <toshiya@med.yokohama-cu.ac.jp>
Furuta
Miyako
M
Fukushima
Atsushi
A
Kimura
Fukuko
F
D000375:Aging / Q000502:physiology; D000818:Animals; D025461:Feedback, Physiological; D005260:Female; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism*; D008297:Male; D009270:Naloxone / Q000494:pharmacology*; D009292:Narcotic Antagonists / Q000494:pharmacology*; D009474:Neurons / Q000187:drug effects* / Q000502:physiology; D009919:Orchiectomy; D010052:Ovariectomy; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D012737:Sex Factors
D009292:Narcotic Antagonists; D016760:Proto-Oncogene Proteins c-fos; D007987:Gonadotropin-Releasing Hormone; D009270:Naloxone; D007986:Luteinizing Hormone