Opiate-androgen interactions in drug-induced yawning and penile erections in the rat

Neuroendocrinology. 1986;42(3):185-90. doi: 10.1159/000124438.


The effects of pretreatment with drugs on drug-induced yawning and penile erection in intact and chronically castrated rats were investigated. Naloxone partially blocked yawning in intact rats and in castrated rats pretreated with dihydro-testosterone propionate (DHTP) but not in control castrates. In contrast, naloxone potentiated apomorphine-induced penile erections in intact rats. Morphine, haloperidol and atropine blocked yawning and penile erections. Methyl naloxone, methyl atropine and domperidone at doses which are selectively peripheral-acting had no effect on drug-induced yawning or penile erection indicating that both effects are mediated centrally. Pretreatment with morphine did not change the naloxone effects in intact rats. The results indicate a naloxone-androgen interaction in drug-induced yawning but the results with morphine are not consistent with a role of opiates in this interaction. The penile erection data support a direct opiate-dopamine receptor interaction in this response. The haloperidol and atropine effects support a cholinergic-dopaminergic interaction in both yawning and penile erections.

MeSH terms

  • Animals
  • Dihydrotestosterone / analogs & derivatives
  • Dihydrotestosterone / pharmacology
  • Drug Interactions
  • Endorphins / physiology*
  • Haloperidol / pharmacology
  • Male
  • Morphine / pharmacology
  • Naloxone / pharmacology
  • Orchiectomy
  • Penis / drug effects*
  • Rats
  • Rats, Inbred Strains
  • Reflex / drug effects*
  • Testosterone / physiology*


  • Endorphins
  • Dihydrotestosterone
  • Naloxone
  • Testosterone
  • Morphine
  • dihydrotestosterone propionate
  • Haloperidol