Temperatura cerebral e ajustes termorregulatórios em ratos espontaneamente hipertensos (SHR) submetidos ao exercício físico até a fadiga em ambiente quente

• Autor(a) principal: Drummond, Lucas Rios
• Data de Publicação: 2014
• Tipo de documento: Dissertação
• Idioma: por
• Título da fonte: LOCUS Repositório Institucional da UFV
• Texto Completo: http://locus.ufv.br/handle/123456789/3493
• topic: Exercícios físicos - Aspectos fisiológicos; Termorregulação; Hipertensão; Physical exercises - Physiological aspects; Thermoregulation; Hypertension; CNPQ::CIENCIAS DA SAUDE::EDUCACAO FISICA

The aim of this study was to evaluate brain temperature and thermoregulatory adjustments in spontaneously hypertensive rats (SHR) during exercise in temperate and warm environments. All experimental procedures were approved by the Ethics Committee on Animal Use at UFV (# 58/2012). Nineteen male Wistar rats (383 ± 11 g, 120 ± 3 mmHg) and eighteen SHR (324 ± 6 g, 196 ± 4 mmHg) with 16 weeks of age were used in the experiments. These animals had their blood pressure measured by tail plethysmography prior to exercise trials. Then, the rats underwent implantation of an abdominal temperature sensor and a guide cannula in the right frontal cortex (AP: +3 mm; ML: -3 mm, DV: -1.8 mm), that allowed us to insert a themorresistor and measure Tbrain. After recovery from surgery, the animals were familiarized to run on a treadmill (15 m/min) for 5 minutes for 5 consecutive days. Then, the animals were subjected to incremental- (initial speed of 10 m/min; speed was increased by 1 m/min every three minutes) or constant-speed (60% of maximal speed throughout the exercise) exercise until they were fatigued in a temperate (25 °C) and warm (32 °C) environment. The brain (Tbrain), abdominal (Tabd) and tail skin (Tskin) temperatures were measured every minute throughout the exercise trials. Data regarding body temperatures were analyzed using two- way ANOVA with split plot and presented as means ± SEM (α=5%). During incremental speed-exercise in temperate environment, the SHR group exhibited greater Tbrain as compared to controls from the 15th min until fatigue, higher Tabd from the 13th min until fatigue and lower Tskin from the 12th to 27th min of exercise. In warm environment, the SHR group presented greater Tbrain from the 7th and 14th min and at fatigue and higher Tabd from the 10th min until fatigue. During constant speed-exercise in temperate environment, the SHR group showed greater Tbrain than controls from 13th and 35th min, higher Tabd from the 19th and 52th min, and lower Tskin from the 4th and 16th min of exercise. In warm environment, the SHR group exhibited greater Tbrain from the 11th and 24th min and higher Tabd from the 9th and 36th min. In addition, SHRs showed lower physical performance in incremental- and constant- speed exercise in both environments. In conclusion, hypertensive animals show an exacerbated increase in brain and abdominal temperatures during acute exercise in temperate and hot environments.