The optimal combination of a
dopamine D2 agonist and a D1 agonist was evaluated for symptomatic treatment of
Parkinson's disease. Behavioral effects of combination treatment of the full D2 agonist
quinpirole or the partial D2 agonist
terguride with the full D1 agonist
SKF 82958 [(I) 6-Chloro-7, 8-dihydroxy-3-allyl-1-phenyl-2, 3, 4, 5-tetra-hydro-1H-3-benzazepine] were investigated in
1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (
MPTP)-lesioned parkinsonian cynomolgus monkeys with attention to the induction of hyperactivity such as irritability, excitability and aggressiveness and of
dyskinesias such as licking of paws, chewing and biting. Both
quinpirole and
SKF 82958 alone improved the
parkinsonism with a slight induction of the hyperactivity and
dyskinesias.
Terguride also improved the
parkinsonism but did not induce the hyperactivity and
dyskinesias. Combination treatment of
quinpirole with
SKF 82958 not only showed a tendency to augment the antiparkinsonian effects but also induced the marked hyperactivity and
dyskinesias. On the other hand, combination treatment of
terguride with
SKF 82958 also augmented the antiparkinsonian effects but did not induce any hyperactivity and
dyskinesias. These findings suggest that combination therapy with a partial D2 agonist and a full D1 agonist or monotherapy with a
dopamine agonist that has both partial D2 and full D1 agonist properties might be beneficial for treating motor dysfunction in
Parkinson's disease without inducing dopaminergic side effects.