Figure 2

Striatal DA release in peak-dose L-3,4-dihydroxyphenylalanine (L-DOPA)-induced dyskinesias (LIDs) and GIDs. (a) Physiological release of DA in the striatum of healthy individuals. (b) Patients with PD who have peak-dose LIDs experience a sharp, short-term, abnormal increase in striatal synaptic DA concentrations when large doses of L-DOPA are administered and reach the extensively denervated striatum. Once the L-DOPA effect wears off, levels of DA drop below normal range. (c) Patients with PD who have striatal DA reinnervation rising to normal levels following transplantation with fetal ventral mesencephalic (VM) tissue experience constant GIDs because of the excessive 5-HT innervation in the grafted striatum. The 5-HT, neuron-derived, irregular levels in synaptic DA concentrations is a phenomenon with prolonged and steady duration and possibly lower intensity compared to LIDs.