Intracerebral grafting of neuronal cell suspensions. III. Activity of intrastriatal nigral suspension implants as assessed by measurements of dopamine synthesis and metabolism.

The activity of intrastriatal grafts of nigral cell suspensions has been monitored biochemically, using radioenzymatic assays of dopamine, its major acidic metabolite, DOPAC, and DOPA accumulation after DOPA-decarboxylase inhibition. Implants of 4-9 microliter of nigral cell suspension restored striatal DA levels by an average of 13-18%, with the highest individual values reaching about 50% of control. DOPAC was restored from about 5% in the lesioned controls to about 20% of normal in the grafted animals. The DOPAC: DA ratios and the DOPA accumulation measures indicated that the grafted DA neurons were spontaneously active and that the transmitter turnover rate was on the average some 50-100% higher than the intact intrinsic nigrostriatal DA neurones. These results thus provide evidence that the intrastriatal nigral suspension grafts are capable of restoring dopaminergic neurotransmission in the previously denervated striatum.