The authors investigated the ability of daytime infusions of apomorphine, a
D-1 and D-2 dopamine agonist, to sustain the long duration response (LDR)
in seven subjects with fluctuating PD in whom L-DOPA was discontinued for 3
days. Apomorphine maintained the LDR to the extent that it kept the subjec
ts "on" during the day. This observation suggests that the LDR can be a pos
tsynaptic effect, independent of dopamine storage.