Metoclopramide decreases apomorphine-induced yawning and penile erection

Acute administration of metoclopramide, a dopamine (D2) antagonist, reduced both apomorphine-induced yawning and penile erections. Metoclopramide, prominent in clinical use as an effective antiemetic, has been shown to be associated with decreased erectile function in humans. Experimentally naive rats were given a standardized dose of apomorphine and one of a range of doses of metoclopramide. The study shows that metoclopramide decreases the erectile response to apomorphine and suggests that the erectile difficulties experienced in humans after metoclopramide treatment may be a result of interference with a central dopaminergic mechanism(s).