Effects of Treadmill exercise on Arterial pressure, Energy Metabolism and Renal Sympathetic Nerve Activity in Rats

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The purpose of the present study is to determine the effects of mild exercise (treadmill, 20m/min over 30 min) on the regulatory system of the arterial pressure and the relative utilization of lipid and carbohydrate for energy metabolism with special references to the sympathetic nervous system in conscious rat.Wister rats weighing 290<plus-minus>29g (SE,n=10) were instrumented chronically with a stainless steel electrode for the measurement of renal sympathetic nerve activity (RSNA) and catheters for the measurements of arterial (Pa) and venous pressure (Pcv) through the femoral artery and vein under anesthesia with pentobarbital sodium (50mg/kg ip.). At least 2 days after the recovery period of sugary, rats ware placed on the treadmill. The experimental procedure is consisted of, 1) 60min resting of home cage, 2) 60 min of resting on the treadmill lane, 3) Exercise (20m/min over 30min), 4) 60 min of recovery on the treadmill lane, 5) 60min of recovery of home cagSystemic arterial pressure increased due to exercise, but it decreased in temporal fashion by 8<plus-minus>2mmHg after the exercise relative to the pre-exercise level. Respiratory quotient decreased in sustained manner after exercise from 0.82<plus-minus>0.02 of the pre-exercise level to 0.72<plus-minus>0.01 of 16-60 min after end of exercise. RSNA also decreased after end of the exercise from 30<plus-mThese data suggest that dynamic exercise induces sustained suppression of the sympathetic nerve activity after end of the exercise in rats. This decreases in sympathetic nerve activity might decrease in total peripheral resistance or cardiac output such that systemic arterial pressure decreased. The sustained reduction of sympathetic nerve activity may be involved in regulating relative utilization of lipid and carbohydrate for energy production after exercise. The mechanisms underlying the sustained decreases in sympathetic nerve activity should be studied in further experiments.