Further Evidence that Gonadal Steroids do not Modulate Brain Opiate Receptors in Male Rats

• Published in: Endocrinologia Japonica Vol. 34; no. 4; pp. 521 - 529
• Main Authors: OLASMAA, MARJUT, LIMONTA, PATRIZIA, MAGGI, ROBERTO, DONDI, DONATELLA, MARTINI, LUCIANO, PIVA, FLAVIO
• Format: Journal Article
• Language: English
• Published: Tokyo The Japan Endocrine Society 1987; Japan Endocrine Society
• Subjects: Animals; Biological and medical sciences; Brain - drug effects; Brain - metabolism; Dihydromorphine - metabolism; Fundamental and applied biological sciences. Psychology; Hormone metabolism and regulation; Luteinizing Hormone - blood; Male; Mammalian male genital system; Morphine Derivatives - metabolism; Orchiectomy; Rats; Rats, Inbred Strains; Receptors, Opioid - drug effects; Receptors, Opioid - metabolism; Receptors, Opioid, mu; Testosterone - blood; Testosterone - pharmacology; Vertebrates: reproduction; Brain; Orchidectomy; Androgen; Rat; Rodentia; Central nervous system; Male; Opiate receptor μ; Biological activity; Testosterone; Vertebrata; Mammalia; Binding capacity; Feedback; Sex steroid hormone
• ISSN: 0013-7219; 2185-6370
• DOI: 10.1507/endocrj1954.34.521

It is still unclear whether, in the male rat, castration and androgen replacement affect the binding characteristics of brain opiate receptors. To clarify this issue, the effects exerted by orchidectomy and testosterone (T) replacement on the subpopulation of brain μ opiate receptors were studied in male rats; testosterone was administered via subcutaneous Silastic capsules. Utilizing 3H-dihydromorphine (a μ receptor ligand) it has been shown that the affinity constant (Ka) of brain μ opiate binding sites, measured in plasma membrane preparations, is not affected by castration. When μ receptor concentrations were measured in individual brains, it was found that gonadectomy and T replacement failed to produce any change in the number of μ opiate receptors. These data suggest that, in male rats, gonadal steroids do not develop their central feedback effects by affecting brain μ opiate receptors.