Abstract
Rationale: SKF 83959 acts as a D1 antagonist in vitro but has been claimed to induce anti-parkinsonian effects after acute administration in MPTP-treated marmosets. Objective: The aim of the present study was to evaluate the therapeutic and undesired effects of subchronic administration of SKF 83959 in bilaterally MPTP-treated rhesus monkeys and to compare these effects with the effects of L-dopa and the dopamine agonist SKF 82958. Methods: MPTP was given in the left carotid artery (2.5 mg) and 6 weeks later, the right carotid artery (1.25 mg). The monkeys (n=4) had previously been treated chronically with L-dopa (22 days, 10 mg/kg) and SKF 82958 (22 days, 1 mg/kg). Three months after the last administration of SKF 82958, SKF 83959 was given in a dose of 0.5 mg/kg from day 1 to day 15 and in a dose of 1.0 mg/kg from day 16 to day 18. Results: SKF 83959 increased goal-directed limb movementsin all animals, including those unresponsive to L-dopa. This therapeutic effect did not diminish during treatment. With respect to body displacement and undesired effects, a large variation in the response to SKF 83959 was found: a large increase in body displacement co-occurred with oro-facial dyskinesia (n=2), whereas a small increase in body displacement co-oc-curred with dystonia (n=2). In contrast to the undesired effects of L-dopa, the dyskinetic effects of SKF 83959 were primarily limited to the first treatment day. Unlike L-dopa and SKF 82958, SKF 83959 did not induce epileptoid behaviour. Conclusion: sub-chronic administration of SKF 83959 induced both clear-cut therapeutic effects that remained stable in time, and a limited number of dyskinetic effects that wore off during the treatment. The dopamine D1, antagonist SKF 83959 may be considered as an alternative treatment in Parkinson's disease, especially in those patients who do not respond to L-dopa.
