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

Pharmacol Biochem Behav. 1980 Sep;13(3):435-41. doi: 10.1016/0091-3057(80)90251-8.


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 adminstration 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 beta-endorphin (6 micrograms) produced a complete loss of copulatory behavior in male rats. The deficit in sexual behavior induced by beta-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.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Brain Chemistry / drug effects
  • Catecholamines / metabolism*
  • Endorphins / pharmacology*
  • Male
  • Morphine / pharmacology*
  • Naloxone / pharmacology*
  • Rats
  • Sexual Behavior, Animal / drug effects*
  • beta-Endorphin


  • Catecholamines
  • Endorphins
  • Naloxone
  • beta-Endorphin
  • Morphine