THERMAL SENSITIVITY IN RATS SUBMITTED TO SWIMMING

Abstract

lntroduction : The swimming has a number of physiological benefits, among which we can mention the increased resistance to the perception of thermal stimuli. The thermal sensitivity is designated as responsive to rising temperature, harmful heat, decrease the temperature and harmful cold. The thermal and painful sensations are transmitted to the central nervous system via axons C, Aõ . The heat-sensitive fibers C are called mecanotermossensíveis C fibers, which require different membrane receptors to make the distinction between various sensory thresholds . These receptors are called channels TRP (transient receptor potential) and are responsible for performing the transduction of thermal signals . The termocepção can be measured by the hot plate test based on the response latency to a given adverse thermal stimulus . Objectives : to determine the thermal sensitivity in rats submitted to swimming. Methods: This study was approved by the Ethics Committee for the Use of Animais (CEUA) of the State University of Ceará (UECE), Official Letter No. 12725887-0. 16 female Wistar rats were used ± 8 weeks , divided into two groups : contrai (C) and swimming (N). The animais swimming starting time duration of 3 minutes for the first week and reaching 36 minutes at the end of the second week with a 5% body weight load tied to the tail, to avoid floating. The exercises in the water were carried out by the morning shift, six days a week and a weekly rest. The animais were then immediately dried by a hot air jet device (sized hair dryer) . Thermal sensitivity was evaluated using the hot plate test at 50º C is considered as a valid positive response and the heel of the animal licks its hind legs and cleaning of the animais forepaws . The results were analyzed by comparing an average between the two groups tested by one-way ANOVA analysis. Statistical analysis was performed using t test for independent samples , assuming significance of p <0.05.

Results and Discussion: As a result, one can observe a significant increase (p = 0.014) in response time to thermal stimulation of the swimming group (5.875 ± 1.060 N = 8) compareci to the contrai group (2.375

± 0.962 N = 8). These results confirm previous studies, which show that swimming is able to increase the nociceptive threshold in rodents, suggesting that exercise the aquatic environment is able to reduce the activation of TRPV1 channels , which are only activated at temperatures between 42 and 52 º C. This mechanism might explain the increased latency response comparing the swimming group with the contrai group. Conclusion: The data demonstrate that swimming increased tolerance to thermal stimuli , which produces a positive effect on the animais, it increases the selectivity of the intensity of painful stimuli perceived by the body.