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 sh own to protect dopamine transporters from methamphetamine-induced neurotoxi city. In the present study, we demonstrate that exposure of embryonic ventr al mesencephalic cells to DADLE (0.01 g/ml). prior to intrastriatal transpl antation. enhanced functional recovery and graft survival in 6-hydroxydopam ine-induced hemiparkinsonian rats. At 6 and 8 weeks posttransplantation, an imals that received DADLE-treated cell grafts exhibited significantly highe r (near normal) spontaneous locomotor behaviors, as well as trends of great er reversal of motor asymmetrical behaviors compared with animals that rece ived nontreated cell grafts. Histological examination revealed that animals transplanted with DADLE-treated cell grafts exhibited about twice the numb er of surviving tyrosine hydroxylase-immunoreactive grafted neurons compare d with those animals that received nontreated cell grafts. These results su ggest that DADLE should be considered as an adjunctive agent for neural tra nsplantation therapy in Parkinson's disease.