Tetrabenazine Mitigates Aberrant Release and Clearance of Dopamine in the Nigrostriatal System, and Alleviates L-DOPA-Induced Dyskinesia in a Mouse Model of Parkinson's Disease

Background: L-DOPA-induced dyskinesia (LID), occurring with aberrant processing of exogenous L-DOPA in the dopamine-denervated striatum, is a main complication of levodopa treatment in Parkinson's disease. Objective: To characterize the effects of the vesicular antagonist tetrabenazine (TBZ) on L-DOPA-induced behavior, neurochemical signals, and underlying protein expressions in an animal model of Parkinson's disease. Methods: 20-week-old MitoPark mice were co-treated or separately administered TBZ and L-DOPA for 14 days. Abnormal involuntary movements (ATMs) and locomotor activity were analyzed. To explore dopamine (DA) transmission, fast scan cyclic voltammetry was used to assess presynaptic DA dynamics in striatal slices following treatments. PET imaging with 4-[18F]-PE2I, ADAM and immunoblotting assays were used to detect receptor protein changes in the DA-denervated striatum. Finally, nigrostriatal tissues were collected for HPLC measures of DA, serotonin and their metabolites. Results: A single injection of TBZ given in the interval between the two L-DOPA/Carbidopa treatments significantly attenuated L-DOPA-induced AIMs expression and locomotor hyperactivity. TBZ was shown to reduce tonic and phasic release of DA following L-DOPA treatment in DA-denervated striatal tissue. In the DA-depleted striatum, TBZ decreased the expression of L-DOPA-enhanced D1 receptors and the serotonin reuptake transporter. Neurochemical analysis indicated that TBZ attenuated L-DOPA-induced surges of DA levels by promoting DA turnover in the nigrostriatal system. Conclusion: Our findings demonstrate that TBZ diminishes abnormal striatal DA transmission, which involves the ability of TBZ to modulate the presymptomatic dynamics of DA, and then mitigate aberrant release of exogenous L-DOPA from nerve terminals. The results support the potential of repositioning TBZ to counteract LID development.