PET studies of the effects of aerobic exercise on human striatal dopamine release

In vivo microdialysis studies have shown that exercise increases the concen tration of dopamine (DA) in the striatum of the rat brain. it has also been shown that PET with [C-11]raclopride can be used to assess changes in brai n DA induced by drugs and by performance tasks such as playing a video game . The purpose of this study was to evaluate the effects of exercise (treadm ill running) on striatal DA release in the human brain. Methods: Twelve hea lthy volunteers (5 women, 7 men; mean age, 32 +/- 5 y; age range, 25-40 y) with a history of regular exercise received 2 PET scans with [C-11]raclopri de on 2 separate days, 1 at baseline and 1 at 5-10 min after running on a t readmill for 30 min. The speed and inclination of the treadmill were increa sed gradually to reach a maximal speed of 9.7 km/h (6 mph) and a maximal in clination of 10 degrees. Data were acquired on a Siemens HR+ scanner in 3-d imensional mode for 60 min. Heart rates and electrocardiograms were monitor ed. DA D-2 receptor availability was measured using the ratio of the distri bution Volume in the putamen to that in the cerebellum, which is a function of the number of available binding sites/dissociation constant. Results: T he subjects ran at an average speed of 8.7 +/- 0.5 km/h (5.4 +/- 0.3 mph) a nd at an inclination of 3.3 degrees +/- 2 degrees. The maximum effort of ru nning was maintained for 10-15 min. The heart rates of the subjects were in creased by 143% +/- 47%. DA Dg receptor availability in the putamen after t readmill running (4.22 +/- 0.34) was no different from that of baseline (4. 17 +/- 0.29; P < 0.6). Conclusion: No significant changes in synaptic DA co ncentration were detected, although the subjects exercised vigorously for 3 0 min.