Opiate-androgen interactions in drug-induced yawning and penile erections in the rat.
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.
D000818:Animals; D013196:Dihydrotestosterone / Q000031:analogs & derivatives / Q000494:pharmacology; D004347:Drug Interactions; D004723:Endorphins / Q000502:physiology*; D006220:Haloperidol / Q000494:pharmacology; D008297:Male; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D009919:Orchiectomy; D010413:Penis / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D012018:Reflex / Q000187:drug effects*; D013739:Testosterone / Q000502:physiology*
D004723:Endorphins; D013196:Dihydrotestosterone; D009270:Naloxone; D013739:Testosterone; D009020:Morphine; C030445:dihydrotestosterone propionate; D006220:Haloperidol