Delta opioid peptide augments functional effects and intrastriatal graft survival of rat fetal ventral mesencephalic cells.

Delta enkephalin analogue [D-Ala(2),D-Leu(5)]enkephalin (DADLE) has been shown to protect dopamine transporters from methamphetamine-induced neurotoxicity. In the present study, we demonstrate that exposure of embryonic ventral mesencephalic cells to DADLE (0.01 g/ml), prior to intrastriatal transplantation, enhanced functional recovery and graft survival in 6-hydroxydopamine-induced hemiparkinsonian rats. At 6 and 8 weeks posttransplantation, animals that received DADLE-treated cell grafts exhibited significantly higher (near normal) spontaneous locomotor behaviors, as well as trends of greater reversal of motor asymmetrical behaviors compared with animals that received nontreated cell grafts. Histological examination revealed that animals transplanted with DADLE-treated cell grafts exhibited about twice the number of surviving tyrosine hydroxylase-immunoreactive grafted neurons compared with those animals that received nontreated cell grafts. These results suggest that DADLE should be considered as an adjunctive agent for neural transplantation therapy in Parkinson's disease.