Significance of testosterone in regulating hypothalamic content and in vitro release of beta-endorphin and dynorphin.
The effects of castration and testosterone replacement on hypothalamic pools of beta-endorphin and dynorphin and on the basal and corticotropin-releasing factor (CRF)-stimulated release of these peptides from hypothalamic slices in vitro were studied. The experiments were done in adult male rats. The hypothalamic content of both peptides increased significantly within 1 week of castration, and levels remained elevated for up to 4 weeks. Testosterone treatment, begun at the time of castration, prevented these increases. In addition, testosterone replacement 6 weeks after castration reversed peptide levels to normal. Basal in vitro release rates of beta-endorphin and dynorphin were significantly lower from hypothalamic slices derived from 1-week castrated animals than from intact males, and when testosterone was administered in various doses in vivo, basal release rates in vitro increased in a dose-related manner. Hypothalami from rats that had been castrated for 4 weeks, however, showed basal release rates similar to those in tissues from intact controls, a finding indicating that castration initially alters both opioid peptide synthesis and release; later, release is normalized, whereas synthesis remains elevated. CRF was found to stimulate beta-endorphin and dynorphin release from hypothalami from intact and from 1- and 4-week-castrated rats, a result indicating that castration does not alter the response of beta-endorphin and dynorphin neurons to this stimulus.
D000818:Animals; D003346:Corticotropin-Releasing Hormone / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004399:Dynorphins / Q000378:metabolism*; D004723:Endorphins / Q000378:metabolism*; D007987:Gonadotropin-Releasing Hormone / Q000378:metabolism; D007031:Hypothalamus / Q000187:drug effects / Q000378:metabolism*; D007986:Luteinizing Hormone / Q000378:metabolism; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000378:metabolism; D009919:Orchiectomy; D051381:Rats; D011919:Rats, Inbred Strains; D013739:Testosterone / Q000494:pharmacology / Q000502:physiology*; D001615:beta-Endorphin
D004723:Endorphins; D007987:Gonadotropin-Releasing Hormone; D013739:Testosterone; D001615:beta-Endorphin; D004399:Dynorphins; D007986:Luteinizing Hormone; D003346:Corticotropin-Releasing Hormone