Regional differences in striatal dopamine uptake and release associated with recovery from MPTP-induced parkinsonism: An in vivo electrochemical study

This study directly assessed striatal dopamine (DA) uptake rates and peak r elease in response to KCI in normal, symptomatic, and recovered 1-methyl-4- phenyl-1,2,3,6-tetrahydropyridine (MPTP)-treated cats using in vivo electro chemistry. DA uptake rates measured after direct application of known conce ntrations of DA to the striatum were slowed significantly in both dorsal an d ventral striatum in symptomatic cats compared with rates recorded in norm al animals. DA uptake rates remained significantly slowed in recovered cats and were not significantly different from the rates recorded in symptomati c animals. In symptomatic cats, both DA uptake rates and the signal recorde d in response to KCI stimulation were significantly decreased from normal i n all dorsal and ventral striatal regions sampled. Reduction/oxidation (red ox) ratios recorded in response to KCI stimulation suggested DA to be the p redominant electroactive species. In spontaneously recovered MPTP-treated c ats. recordings in the ventral striatum subsequent to KCI stimulation again suggested DA to be the predominant electroactive species released, and pea k levels were significantly higher than those recorded in symptomatic anima ls. In the dorsal striatum of recovered cats, redox ratios recorded subsequ ent to KCI stimulation suggested serotonin rather than DA to be the predomi nant electroactive species released. Peak levels of release in the dorsal s triatum were not significantly greater than those recorded in symptomatic a nimals. These results suggest that in spontaneously recovered MPTP-treated cats, there is partial recovery of ventral striatal DAergic terminals, pers istent loss of dorsal striatal DAergic terminals, and a down-regulation of DA transporter number/function throughout the striatum. These processes may contribute to Volume transmission of DA in the striatum and promote functi onal recovery.