The Research On Stress Response Mechanism Of Hypothalamus-Pituitary-Adrenal Axis In Different Exercise Stress State

Objective: Exercise Stress is the biological basis of sports training and sports fitness that can produce effects. However, there was less study of the central response mechanism of HPA axis in exercise stress. In particular, there was no report on the study of HPA axis regulation affected by NO through the combination of glucocorticoid receptor (GR) and glucocorticoid (GC) as well as the changes of GR NOS in HPA Axis central regulatory systems. The research took different load treadmill exercise- induced stress state as the research objective. It analysed different load of exercise stress level of HPA axis and central regulatory rule from the change of the levels of peripheral hormones HPA axis, central-related receptor gene and protein expression, and so on. It revealed the central regulatory mechanisms in the stress of different exercise load.Methods: 11-week 130 male SD rats were randomly divided into three groups: long-term exercise group, one exercise group and control group. The rats of that long-term exercise group were trained to run on the treadmill with three different loads: high-load, middle-load, and low-load, 6 days/week, one hour/day, and the experimental period was 8 weeks. One exercise group was also divided into three different load movements, adopting the last sports program of the same load of the long-term group. Testing methods and indices: It determined the content of serum CORT, T, ACTH, hypothalamic CRH levels with the method of double-antibody sandwich enzyme linked immunosorbent. With the method of Immunohistochemistry, it tested hippocampal CA1, hypothalamic arcuate nucleus, ventromedial nucleus, dorsomedial nucleus, paraventricular nucleus, central amygdaloid nucleus, and observed the morphological changes, determining the number of changes of GR, NOS-positive neurons, and so on. With the method of PT-PCR, it determined the gene transcription level of hippocampus, hypothalamus, and amygdala GR, MR, NOS. With the method of Western blotting, it determined the protein expression of GR and NOS of the above-mentioned nuclei.Results:(1) Hippocampus MR, GR transcription in the long-term heavy load exercise group decreased, and GR expression also decreased(P<0.05). Transcription and expression of NOS did not change significantly. The excitability in hypothalamus was elevated. GR, MR transcription decreased. NOS expression increased (P<0.05). GR gene transcription in the amygdale had no significant change, and NOS gene transcription in the amygdale increased (P<0.05). ACTH increased, but CRH, CORT concentration decreased.(2) Hippocampus GR, NOS gene transcription and expression increased in the long-term moderate load exercise group (P<0.01). The excitability in Hippocampus decreased, whereas the excitability in hypothalamus was elevated. GR transcription decreased, but protein concentration increased. NOS gene transcription and expression increased (P<0.05). Amygdala excitability increased; GR, NOS gene transcription and expression decreased, and the nuclei of MR decreased; CRH, ACTH, CORT concentration increased (P<0.05).(3) Hippocampal excitability in the long-term low-load exercise group had no significant change. MR gene transcription increased, whereas GR transcription level decreased. NOS gene transcription and expression increased (P<0.05); hypothalamus was excited. NOS, GR gene transcription and expression increased (P <0.05); NOS gene transcription and expression in amygdala decreased. GR gene transcription and expression showed no significant changes. MR gene transcription in the amygdala and hypothalamus decreased, CRH, CORT concentration increased. ACTH had no significant changes.(4) Hippocampus NOS gene transcription and expression increased in heavy load exercise group. GR gene transcription increased, but MR gene transcription decreased. Hippocampal excitability decreased. The excitability of hypothalamus decreased. NOS gene transcription and expression increased. GR, MR gene transcription decreased, whereas GR protein increased ( P<0.05 ) . Amygdala excitability decreased. NOS, GR gene transcription and expression decreased. MR gene transcription increased (P<0.05); CRH, CORT concentration increased, whereas ACTH concentration decreased (P <0.05).(5) Hippocampal NOS gene transcription and expression in moderate load exercise group increased. The level of GR gene transcription and expression decreased. There was no significant change in hippocampal excitability. Hypothalamic paraventricular nucleus was excited, and NOS gene transcription and expression increased. There was no change in the level of GR gene transcription, and the expression increased(P<0.05); GR gene transcription and expression in amygdala increased, whereas NOS gene transcription decreased. NOS concentration increased, but MR transcription of the nuclei decreased (P<0.05). CRH, CORT concentration increased, but ACTH concentration decreased.(6) There was no change in hippocampus excitability in a low-load exercise group. NOS, GR gene transcription and expression decreased. There was no change in MR gene transcription; Excitability of hypothalamic increased. NOS gene transcription showed no significant changes. NOS expression increased, GR gene transcription and expression increased, amygdala excitability increased, and NOS gene transcription and expression increased. GR gene transcription showed no significant changes, and expression increased. MR gene transcription of amygdala and hypothalamus decreased (P<0.05); CRH, CORT concentration increased, but ACTH concentration decreased (P<0.05).Conclusions(1) The stress of long-term heavy load exercise led to the decrease of the excitability in hypothalamus and amygdala, and the suppression of HPA Axis. The stress of one heavy load exercise led to the increase of the excitability in hypothalamus and amygdala. HPA axis was activated.(2) The suppression of hippocampal of long-term heavy load post-exercise was led by the injury of the hippocampus excitability. The suppression of hippocampus of one heavy load exercise was due to peripheral glucocorticoid feedback regulation.(3) In the response of the exercise stress, the excitability of the hippocampus had no correlation with NOS. NOS had participated only in the hippocampus excitatory damage, not participated in the regulation of their excitability.(4) The main difference of HPA axis of the long-term moderate load exercise and one moderate load exercise lied in the change of ACTH. The rise of ACTH of long-term moderate load exercise was due to the participation of the regulation to pituitary between the amygdale and NOS. The decrease of ACTH one moderate load exercise was caused by negative feedback regulation of peripheral GC, and GR of hypothalamus and amygdala.(5) There was no significant change for hippocampal excitability of low-load post-exercise. However, the excitability in amygdala and hypothalamus was elevated. After a long-term low-loaded exercise, amygdala NO participated in the regulation of pituitary ACTH. ACTH of one loaded exercise decreased, which was affected by the feedback regulation of GC and hippocampus GR.(6) The stress response of central regulation of HPA axis of a long-term exercise was more than peripheral regulation. One exercise gave priority to HPA axis feedback regulation of various sectors.