Mechanism of action of L-leucyl-glycinamide and its effect on Parkinson's disease.

PLG potentiates the action of levodopa in 6-OH-DA-treated rats. PLG plus levodopa is more effective than levodopa alone. PLG-treated rats have a decreased concentration of Leu-enkephalin in the caudate nucleus as compared with the control. Preliminary results of using PLG (400 mg/day) for 10 days for treating PD are satisfactory. The mode of action of PLG with relation to dopamine-enkephalin interaction is discussed.