The influence of piribedil (ET495) on components of locomotor activity

Recent evidence suggests piribedil affects both cerebral NA neurones and DA neurones and receptors since it increases brain MOPEG-SO4, an observation confirmed presently. In the reserpinised mouse piribedil and apomorphine caused a reversal of akinesia, which was significantly enhanced by concurrent administration of clonidine. However, piribedil neither reduced nor increased the motor effects of apomorphine or L-DOPA in the reserpinised mouse, but slightly enhanced that of amphetamine. Phenoxybenzamine reduced the motor action of L-DOPA but had no effect on that of apomorphine or amphetamine. These results suggest piribedil has no significant NA receptor blocking or stimulating action in the reserpinised animal. They confirm the view that piribedil increases cerebral NA turnover due to a presynaptic action on NA neurones.