论文部分内容阅读
Objective At present, there have been few reports about whether nitric oxide (NO) in central nervous system is involved in the regulation of exercise performance and fatigue-induced stress.Furthermore, because there is difference among exercise patterns, sampling regions and sampling time, assay methods in published reports, the results about central NO in exercise-induce fatigue were inconsistent.To picture the relationship between central NO and exercise-induced fatigue, studies were performed to assess (1) the effects of exhaustive exercise on central NO level, (2) the effects of modulation of central NO pathway on rats exercise performance and NOs role in modulation of fatigue stress through intracerebroventricular (i.c.v.) microinjeetion of L-arginine (L-Arg), a NO precursor, and L-nitro-arginine methyl ester (L-NAME), a nitric oxide synthase (NOS)inhibitor.Methods Rats were randomly assigned to five groups: control group, exhausted group, saline/exhausted group, L-Arg/exhausted group, and L-NAME/ exhausted group.After recovery from surgery that a cannula was implanted into the lateral cerebral ventricle of the male SD rats, rats were injected with normal saline, L-Arg or L-NAME for four consecutive days.Then, a one-time exhaustive treadmill exercise (on the speed of 18 m/min, an inclination of 5°) was performed.The time of exercise till exhaustion was recorded and total workload was calculated, which represented the running performance.The levels of nitrate/nitrite (NOx) in plasma, hypothalamus and hippocampus after exhaustive treadmill exercise were assayed by a colorimetric technique.Results (1) Compared with those in the control group, plasma NOx level and usea nitrogen concentration was significantly increased in the exhausted group (P < 0.01).The hypothalamic NOx level decreased significantly in the exhausted group (P < 0.001), but there was no significant change of NOx level in hippocampus.Results from an open-field test showed that the locomotor activity at pre-surgery, pre-injection and preexercise had no significant differences among saline/exhausted group, L-Arg/exhausted group and L-NAME/exhausted group.(2) Injection (i.c.v.) of L-Arg or L-NAME had significant effects on exercise performance.Compared with those in the saline/exhausted group, the time of exercise till exhaustion and total workload increased by 151.8% and 150.08% respectively in the L-Arg/exhausted group (P < 0.05), and decreased by 70.22% and 68.90% respectively in the L-NAME/exhausted group (P < 0.01).(3) Injection (i.c.v.) of L-Arg or L-NAME had significant effects on NOx levels in hypothalamus and hippocampus after exhaustive exercise.Injection of L-NAME resulted in marked decreases of NOx level in hypothalamus and hippocampus (P < 0.05, P < 0.001 respectively) as compared with saline injection.Compared with those in the saline/exhausted group, hypothalamic NOx levels was increased in the L-Arg/exhausted group (P < 0.001), but there was no significant change of NOx level in hippocampus.Conclusion Modulation of central NO signaling pathway by i.c.v injection of L-Arg or L-NAME can affect rats exercise performance in exhaustive exercise.The down-regulation of NO in hypothalamus and hippocampus may contribute the low exercise performance and fatigue-induced stress.Hypothalamus may be a key brain region in regulation of exercise performance for central NO.L-Arg supplementation may improve exercise performance and delay the emergence of exercise-induced fatigue through L-Arg-NO signaling pathway.