Comparison of motor response to apomorphine and levodopa in Parkinson's disease. The magnitude and pattern of motor responses to single doses of subcutaneous apomorphine and oral levodopa were compared in 14 patients with Parkinson's disease. Although apomorphine produced much shorter motor responses than levodopa, the quality of response to the two drugs was virtually indistinguishable. These clinical observations support the notion that integrity of striatal post-synaptic dopamine receptors is a key determinant of responsiveness to dopaminergic treatment in Parkinson's disease. 