The impact of alcohol ingestion on erections in rats as measured by a novel bio-assay

In rats, a syndrome of yawning and penile erection results from the administration of low doses of apomorphine, a dopamine receptor agonist shown to stimulate dopamine autoreceptors. Ethanol has been shown to influence dopamine metabolism. Low doses of ethyl alcohol (0.25 mg./kg.) failed significantly to alter apomorphine-induced yawning or penile erection, while 0.5 mg./kg. decreased erectile behavior but did not significantly alter the number of yawns. A reduction in both yawning and penile erection in response to apomorphine challenge was seen after the acute intraperitoneal injection of relatively high doses (1.0-3.0 mg./kg.) of ethanol. Two possible mechanisms of action may explain these phenomena. Alcohol may interfere with dopaminergic receptor mechanisms, or conversely, alcohol, through its actions on central dopamine metabolism may alter a second neurotransmitter/neuropeptide more directly responsible for the production of apomorphine-induced yawning and penile erection, possibly oxytocin.