Four Cebus apella monkeys with persistent dyskinetic movements induced by earlier long-term administration of
haloperidol were subjected to a trial of the
dyskinesia-modifying effects of a novel
dopamine autoreceptor agonist
3-PPP (3[3-hydroxyphenyl]-N-n-propyl-
piperidine). Three monkeys had choreic
dyskinesia involving trunk and extremities whereas one had a buccolingual form including tongue protrusion with choreoathetotic twitching and twisting movements of the tongue. Two monkeys (1 choreic, 1 buccolingual) responded with dose-dependent symptom alleviation to
3-PPP, 1-4 mg/kg, with no signs of concomitant sedation or
catalepsy. In the monkey with buccolingual
dyskinesia all dyskinetic signs disappeared completely 2 hours after 2 mg/kg of
3-PPP. This animal participated in a separate study where the same doses of
3-PPP but also its enantiomers were given. The (-) enantiomer was a more potent antidyskinetic agent than the (+) enantiomer, the racemate falling between these two. Four mg/kg of the (+) enantiomer precipitated an
amphetamine-like excitation and after 4 hours aggravation of
dyskinesia was noted. These observations support the notion that the (+) enantiomer has both postsynaptic and presynaptic stimulatory effects, whereas the (-) enantiomer acts as a presynaptic
dopamine receptor agonist.