Cycloheximide prevents apomorphine-induced yawning, penile erection and genital grooming in rats

Apomorphine (50 micrograms/kg) induced repeated episodes of yawning, penile erection and genital grooming in rats. A dose of cycloheximide, which inhibited brain protein synthesis by 50% totally prevented apomorphine-induced yawning and reduced by approximately 50% the occurrence of episodes of penile erection and genital grooming. However, this treatment failed to modify the stereotyped behaviour induced by 200 micrograms/kg of apomorphine. These results suggest that protein synthesis is required for the behavioural effects of small doses of apomorphine.