Effects of morphine, β-endorphin and naloxone on catecholamine levels and sexual behavior in the male rat

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Abstract

Intraperitoneal administration of the opiate antagonist naloxone hydrochloride (30 mg/kg) to sexually experienced male rats caused a significant reduction in mount and intromission latencies, number of mounts preceding ejaculation and ejaculation latencies. Intraperitoneal administration of naloxone (30 mg/kg) also stimulated persistant non-copulators to begin mating and to ejaculate within a twenty minute test period. Conversely, intraperitoneal administration of morphine sulphate (6 mg/kg) as well as intraventricular injection of the endogenous opiate β-endorphin (6 μg) produced a complete loss of copulatory behavior in male rats. The deficit in sexual behavior induced by β-endorphin was correlated with a significant increase in hypothalamic norepinephrine levels. It is suggested that the endogenous opiates may be involved in the mediation of sexual behavior via an interaction with central catecholaminergic systems.

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    • Cited by (0)

    1

    Present address: Department of Surgery—L-910, Boston University Medical Center, 80 East Concord Street, Boston, MA 02118.

    2

    Present address: Memorial Sloan Kettering Cancer Center, Department of Endocrinology—H904, New York, NY.

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