Blockade of Central Dopaminergic Signaling Reduces Treadmill Running Performance of Rats
Authors: Rodrigues Quezia Teixeira , Lima Paulo Marcelo Andrade , Drummond Lucas Rios , Machado Frederico Sander Mansur , Campos Helton Oliveira , Leite Laura Hora Rios , Coimbra Cândido Celso 
Published: November 2023

IntroductionDuring aerobic exercise core body temperature (Tb) rises simultaneously with changes in the contents of central neurotransmitters that are related with central fatigue. Dopamine is a central amine that acts on thermoregulation, motor control and the reward system and has been implicated in increased exercise performance.AimThe aim of this study was to verify the role of dopamine receptor type 1 (D1) on physical performance and thermoregulatory control during exercise.MethodsAll experimental protocols were approved by CEUA‐UFMG n. 170/2015. Adult male Wistar rats (n=15; 319 ± 6.5 g of b.w.), after an adaptation period in a treadmill, were subjected to an incremental speed test until fatigue (IE). After that, the animals randomly received an intracerebroventricular injection of NaCl (0.15 M, SAL, control group, n=15) or SCH‐23390 (10 nmol, SCH, D1‐Receptor blocker, n =15), and then underwent to a submaximal exercise protocol until fatigue (70% of Vmax achieved in IE). Another group of animals that received NaCl 0.15 M (SALtSCH, n = 8) performed another situation in which the exercise was interrupted at a time that corresponded to the duration previously reached when treated with SCH‐23390. Exercise time (ET) and workload (W) were measured; Tb and tail skin temperature (Tt) were continuously recorded; and the body heating rate (HSR) and heat storage (HS) were calculated during exercise. Ninety minutes after the end of exercise protocol, the animals were anesthetized and transcardiacally perfused; the brains were analyzed by immunohistochemical assay to determination of c‐Fos expression in thermoregulatory nuclei.ResultsThe blockade of D1 receptor reduced the physical performance (ET: 59.2 ± 7.13 min, SAL, vs 13.0 ± 1.25 min, SCH, p<0.001; W: 14.1 ± 1.72 kgm, SAL, vs 3.00 ± 0.27 kgm, SCH, p<0.001). Moreover, the dynamic phase of exercise was similar in both experimental conditions without differences in BHR and HS, which probably resulted in resembling changes on both Tb and Tt. During the first 10 min of recovery, the reduction of Tb in the SAL‐situation was more efficient when compared to both SCH and SALtSCH situations (DTb: −0.36 ± 0.09 °C SAL vs −0.12 ± 0.14 °C SCH vs −0.06 ± 0.16 °C SALtSCH; p<0.05). Regarding the central nervous system activation, exercise until fatigue increased c‐fos expression in all investigated nuclei regardless of D1 blockade, except for the MPO. Interestingly, SCH‐23390 treatment before exercise induced an increase in neuronal activation in MnPO (81%; p=0.018), in PVN (116%; p=0.015) and in SON (63%; p=0.042) when compared with control animals running for a similar duration (SALtSCH).ConclusionThe data of the present study suggest that the D1 receptor is important for the modulation of the physical performance during running exercise, but this ergolytic effect does not seem to be directly involved with the central nuclei directly implicated in the thermoregulatory adjustments required during exercise.Support or Funding InformationFAPEMIG, CNPq and CAPES