Performance-enhancing and thermoregulatory effects of intracerebroventricular dopamine in running rats

To assess the role of central dopamine on metabolic rate, heat balance and running performance, 2.0 µL of 5 × 10− 3 M dopamine solution (DA) or 0.15 M NaCl (SAL) was intracerebroventricularly injected in Wistar rats 1 min before running on a motor-driven treadmill, according to a graded exercise protocol, until fatigue. Oxygen consumption (VO2) and body temperature (Tb) were recorded at rest, during exercise, and after 30 min of recovery. DA induced a marked increase in workload (~ 45%, p < 0.05). At fatigue point, DA-injected rats attained ~29% higher maximum oxygen consumption (VO2max) and ~0.75 °C higher Tb than SAL-injected rats. Despite the higher VO2max and Tb attained during exercise, DA-treated rats reached VO2 basal values within the same recovery period and dissipated heat ~33% faster than SAL-treated rats (p < 0.05). The mechanical efficiency loss rate was ~40% lower in DA than in SAL-treated rats (p < 0.05), however, the heat storage was ~35% higher in the DA group (p < 0.05). Our results demonstrate that increased DA availability in the brain has a performance-enhancing effect, which is mediated by improvements in the tolerance to heat storage and increases in the metabolic rate induced by graded exercise. These data provide further evidence that central activation of dopaminergic pathways plays an important role in exercise performance.