The Effect Of Thermal Environment On Hypothalamic Extracellular Fluid Monoamine Neurotransmitter Of Recovering From Exhaustive Swimming Rats

Objective: To observe in the thermal environment the changes of monoamine neurotransmitter content and their metabolism in the hypothalamic after exhaustive swimming24hours recovering, analysis the metabolism of them, to provideexperimental basis for exploring the exercise-induced central fatigue and the mechanisms of its recovery in the thermal environment.Method:35SD male rats were randomly divided into the quiet in roomtemperature group, exhaustive exercise in room temperature group, quiet in thethermal environment group, exhaustive exercise in the thermal environmentgroup,and the equilibrium time group. The exhaustive exercise group swimmingto exhaustion and anesthesia. The skull was exposed and a guide cannula wasimplanted through a bore hole in the right hypothalamic by brain-dimensionalpositioning system. Then the microdialysis probe was inserted through the guide.The probes were connected to a microinfusion pump and perfused with amodified Ringer’s solution at a constant flow rate of2μl/min. The sampling ofthe dialysates began120min after probe implantation. Respectively, afterexhaustive exercise,4hours,5hours,6hours,8hours, and24hours to collectthe microdialysis samples. The samples were determined by CE-LIF.Results: In rat hypothalamic recovery period: In exhaustive exercise in roomtemperature group the extracellular5-HT concentration was significantly higherthan the level of quiet. Its changes showed up then decline, and5hours after exercise to achieve maximum value, after exercise24h were still significantlyhigher than the quiet level; The extracellular DA concentration was significantlylower than the level of quiet.5-HT, DA, NE levels were significantly elevated inquiet in the thermal environment group, and the recovery period showed adownward trend. The trends in quiet in the thermal environment as the same ofroom temperature,5-HT levels were significantly elevated at8hours afterexercise.Conclusion: The Tcorewere significantly elevated after rat exhaustive in athermal environment, and reduced the exercise time, lead to decreased exercisecapacity. Exhaustive exercise recovery not only the hypothalamic DA,5-HT themetabolic recovery of delayed its release also has a delayed recovery.24-hourrecovery after exhaustive exercise have not yet completed; the extracellularDA/5-HT was significantly lower than quiet level,24-hour recovery periodinhibitory neurotransmitter still plays a dominant role.5-HT, DA, NE levelswere significantly elevated in quiet in the thermal environment, increase the heatgenerated and reduce the thermal diffusion, resulting in body Tcore.5-HT levelswere significantly elevated after rat exhaustive in thermal temperature, TcoreIncreased even more evident, DA and NE content decreased, cause the body toreduce heat tolerance, accelerate the fatigue and reduced exercise capacity.