title: Age- and sex-specific changes in naloxone-induced luteinizing hormone secretion and Fos expression in gonadotropin-releasing hormone neurons of gonadectomized rats.
abstract: 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.
authors.affiliation: 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>
authors.forename: Toahiya
authors.initials: T
authors.lastname: Funabashi
authors.forename: Miyako
authors.initials: M
authors.lastname: Furuta
authors.forename: Atsushi
authors.initials: A
authors.lastname: Fukushima
authors.forename: Fukuko
authors.initials: F
authors.lastname: Kimura
mesh_terms: 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
chemical_list: D009292:Narcotic Antagonists; D016760:Proto-Oncogene Proteins c-fos; D007987:Gonadotropin-Releasing Hormone; D009270:Naloxone; D007986:Luteinizing Hormone