This study aimed to evaluate brain temperature (Tbrain) changes in spontaneously hypertensive rats (SHRs) subjected to two different physical exercise protocols in temperate or warm environments. We also investigated whether hypertension affects the kinetics of exercise-induced increases in Tbrain relative to the kinetics of abdominal temperature (Tabd) increases. Male 16-week-old normotensive Wistar rats (NWRs) and SHRs were implanted with an abdominal temperature sensor and a guide cannula in the frontal cortex to enable the insertion of a thermistor to measure Tbrain. Next, the animals were subjected to incremental-speed (initial speed of 10 m/min; speed was increased by 1 m/min every 3 min) or constant-speed (60% of the maximum speed) treadmill running until they were fatigued in a temperate (25°C) or warm (32°C) environment. Tbrain, Tabd and tail skin temperature were measured every min throughout the exercise trials. During incremental and constant exercise at 25°C and 32°C, the SHR group exhibited greater increases in Tbrain and Tabd relative to the NWR group. Irrespective of the environment, the heat loss threshold was attained at higher temperatures (either Tbrain or Tabd) in the SHRs. Moreover, the brain-abdominal temperature differential was lower at 32°C in the SHRs than in the NWRs during treadmill running. Overall, we conclude that SHRs exhibit enhanced brain hyperthermia during exercise and that hypertension influences the kinetics of the Tbrain relative to the Tabd increases, particularly during exercise in a warm environment.

This study investigated the effects of manipulating the load components of aerobic training sessions on the physical performance of rats. To achieve this purpose, adult male Wistar rats were divided into four groups: an untrained control (CON) group and training groups with a predominant overload in intensity (INT) or duration (DUR) or alternating and similar overloads in intensity and duration (ID). Prior to, during, and after 8 weeks of the control or training protocols, the performance of the rats (evaluated by their workload) was determined during fatiguing, incremental-speed treadmill running. Two additional incremental running tests were performed prior to and at the end of the protocols to measure the peak rate of oxygen consumption (VO2peak). As expected, the rats in the trained groups exhibited increased performance, whereas the untrained rats showed stable performance throughout the 8 weeks. Notably, the performance gain exhibited by the DUR rats reached a plateau after the 4th week. This plateau was not present in the INT or ID rats, which exhibited increased performance at the end of training protocol compared with the DUR rats. None of the training protocols changed the VO2peak values; however, these values were attained at faster speeds, which indicated increased running economy. In conclusion, our findings demonstrate that the training protocols improved the physical performance of rats, likely resulting from enhanced running economy. Furthermore, compared with overload in duration, overload in the intensity of training sessions was more effective at inducing performance improvements across the 8 weeks of the study.

No abstract

No abstract

This study aimed at investigating the changes in brain temperature (Tb) in SHR subjected to acute physical exercise in temperate and warm environments. Adult male Wistar and SHR rats were subjected to implantation of an abdominal temperature (Ta) sensor and a guide cannula in the right frontal cortex, that allowed us to insert a themorresistor and measure Tb. After recovery, the animals were familiarized to run on a treadmill, and then, in alternate days, they were subjected to two constant‐speed protocols until fatigue (temperate and warm environments). The tail skin temperature (Ts), Ta and Tb were recorded. In the temperate environment, the SHR group ​​showed greater increase in Tb compared with Control group from the 13th min until the 35th min, greater increase in Ta from the 19th min until the 52th min, and lower tail skin temperature from the 13th until the 21th min of exercise. In the warm environment, the SHR group ​​showed greater increase in Tb from the 11th until the 24th min, and greater increase in Ta from the 9th min until the 36th min. The SHR group exhibited lower physical performance compared with the Control group in temperate and warm environments. We conclude that during acute exercise in temperate and warm environments, hypertensive rats present greater increases in Tb and Ta. Fapemig, Capes, and Cnpq.