Administration of naloxone (SC 5 mg/kg) significantly reduced ejaculation and mounting in male rats in the weeks following castration. A similar effect was obtained by injecting morphine (SC 1 or 5 mg/kg). In contrast, the same dosages of naloxone or morphine did not affect the sexual performance of gonadally intact males. Opioid peptides may contribute to the temporary persistence of sexual behavior in testosterone-deficient male mammals, in which incentive qualities of the female partner are an important determinant of sexual arousal. © 1985.
Lieblich, I., Baum, M. J., Diamond, P., Goldblum, N., Iser, C., & Pick, C. G. (1985). Inhibition of mating by naloxone or morphine in recently castrated, but not intact male rats. Pharmacology, Biochemistry and Behavior, 22(3), 361–364. https://doi.org/10.1016/0091-3057(85)90032-2