Reactive capacity: a sensitive behavioral marker of movement initiation and nigrostriatal dopamine function.

Thirty-two Long Evans male rats with sham operations or unilateral 6-OHDA-induced damage to meso-telencephalic dopaminergic neurons were evaluated on a reactive capacity task that demanded high speed movement initiation. The task required lever manipulation to avoid signalled shock. The interval between the warning and the shock was incrementally reduced. A one-sleeved vest provided the opportunity to measure movement initiation of each limb independently. Extent of lesion was assessed by [3H]DA uptake, [3H]spiroperidol binding, or DA levels. Movement initiation latencies for each forelimb were found to be linearly related to interhemispheric striatal DA asymmetry induced by microinjections of 6-OHDA. Even those lesions resulting in small to moderate decreases in DA function, including deficits causing no chronic posture or sensory asymmetries, resulted in reactive capacity deficits and greatly slowed reaction time in the paw contralateral to the lesion. Following severe lesions, small yet substantial deficits were also seen in ipsilateral paw performance, which may be related to DA depletions found in the non-lesioned striatum. Thus, a reactive capacity task which requires the animal to react with maximal speed appears to be a potentially good index of nigrostriatal dopamine integrity even when the depletion is not severe.

The effects of exercise training on [3H]-spiperone binding in rat striatum.

Thirty male Sprague-Dawley rats 100 days of age were divided into three groups: interval trained, endurance trained, and pair-weighted controls. Both trained groups ran up to one hour per day, 6 days per week for 12 weeks. The interval trained group ran up to 20 repeat intervals at 54 meters per minute for 30 seconds, while the endurance trained group ran at 27 meters per minute for 60 minutes. The animals were sacrificed, and the effects of aerobic training were documented by measuring cytochrome oxidase activity in the mixed quadriceps muscles. The cytochrome oxidase activity of the interval and endurance trained groups increased 49%, and 31% respectively, above the control group. [3H]-spiperone was used to label dopamine receptors in the striatum. The endurance group was not significantly different from the interval group in [3H]-spiperone receptor binding, so the two exercise groups were combined to form one group of runners. The runners had significantly higher [3H]-spiperone receptor binding than the controls, F(1,26) = 4.87, p less than 0.05. The mean and standard error for receptor binding was 89 +/- 13 fmoles/mg protein for the runners and 60 +/- 5 fmoles/mg protein for the controls.