Motor response to apomorphine in patients with Parkinson's disease with long-duration response to levodopa

The authors studied the motor response to apomorphine before and 1 year after levodopa therapy in 12 patients with Parkinson's disease. At the 1-year evaluation, the basal tapping score, recorded after a 12-hour levodopa withdrawal, was higher compared with the test performed while patients were de novo, indicating the presence of a long-duration response to levodopa. The amplitude (net increase) of the motor response to apomorphine was similar before and during levodopa therapy. However, because of the better baseline, the maximal tapping score was higher during levodopa therapy. The duration and the latency of the motor response to apomorphine did not change. The presence of a short-duration response to apomorphine, in the presence of a long-duration response to levodopa, may imply that either different compartment (i.e., postsynaptic versus presynaptic) or transduction pathways are involved in such responses.