Dopamine Regulation Of Disengagement In The Basal Ganglia Circuitry

Evidence suggests that dopamine (DA) is crucial for initiation and termination as well as sustained execution of movement. For the present study, it was hypothesized that DA plays a more important role in initiation and termination of movement than in its sustained production. To test these hypotheses, rats were trained to walk on a treadmill in a continuous and discontinuous (walk 30 secs/stop 15 seconds) fashion for one hour while striatal DA samples were collected using In Vivo Microdialysis (IVMCD). We predicted larger increases during discontinuous compared to continuous walking. It was found that brain dialysate levels of DA consistently increased from baseline to walking [p\u3c0.05]. However, no significant difference was found in brain dialysate DA between continuous and discontinuous walking [p\u3e0.05]. Similar to DA, its major metabolites DOPAC and HVA, and the serotonin metabolite 5-HIAA, increased during treadmill walking from resting state levels [p\u3c0.05]. None of these metabolites showed a significant difference between continuous and discontinuous walking. The results of the present study are important because they demonstrate that 1) increases in movement-related changes in brain dialysate dopamine are detectable in contrast to many of the studies in the literature; and 2) the converging changes in DA and its metabolites might be used to monitor changes in functional utilization. In conclusion, a clear understanding for the modulatory role of DA in movement production is crucial for the development of biomedical interventions involving basal ganglia disease