Abstract The behavioral effects of DCMB (2,3-dichloro-α-methylbenzylamine, Lilly), an inhibitor of brain phenylethanolamine- N-methyltransferase (PNMT; EC 22.214.171.124), were studied in rats and mice. The drug decreased spontaneous motor activity and induced stereotypic gnawing in both species. The motor activity response of rats to d-amphetamine was enhanced after DCMB, and unusual stereotypic head bobbing developed. The stereotypic motor responses of mice to morphine were increased after DCMB. These findings suggest that adrenaline neurons (which project to the extrapyramidal system) are involved in normal motor activity and in the suppression of some forms of stereotypy.