| Objective To investigate the effects of aerobic exercise on open-field behavior, serum concentrations of hydrocortisone (CORT) and interleukin-1β(IL-1β), expression of heat shock protein 70 (HSP70) and inducible nitric oxide synthase (iNOS) in hippocampus and prefrontal cortex of chronic unpredicted mild stressed (CUMS) rat exposed to acute stress and explore the effects of aerobic exercise as the non-pharmacological coping strategy on the nervous, endocrine and immune systems during stress procedure. Method Thirty-two adult male Wistar rats were randomly divided into four groups: the control group, the CUMS model group, the labetalol group and the exercise group, with eight rats in each group. The rats of the latter three groups received 21 days of chronic unpredictable mild stress. Rats in labetalol group received a daily intragastric administration of labetalol (30.0mg/kg) 30 minutes before the stressors exposure. Rats in exercise group were trained by a progressively increasing moderate swimming program. All the animals received the acute stress of inescapable footshock after the period of 21 days' CUMS. The open-field test was used to investigate the behavior of the rats. Concentrations of serum CORT and IL-1βwere measured using radioimmunoassays. Immunohistochemistry was adopted for localization of HSP70 in hippocampus and prefrontal cortex. And Western blotting was used for quantitation of HSP70 and iNOS in these two brain areas. Result (1) Compared with the control group, the animals of CUMS group showed significantly prolonged time staying in the centre square (P<0.05), lower locomotor activities of both crossing and rearing (both P<0.01), and less grooming numbers (P<0.05); the rats in labetalol group exhibited longer time staying in the centre square (P<0.05), less numbers of both rearing and grooming (P<0.01 and P<0.05, respectively). Compared with the CUMS group, the animals in exercise group showed the shorter time staying in centre square (P<0.01), the more numbers of crossing (P<0.01), rearing (P<0.01), and grooming (P<0.05). The rats in labetalol group exhibited longer time staying in the centre square (P<0.05), less numbers of both rearing and grooming (P<0.01; P<0.05) than exercise group. (2) The level of serum CORT of exercise group was higher than that of the CUMS group and labetalol group (both P<0.05). There was no significant difference of serum IL-1βlevels among the groups. (3) Compared with the CUMS group, the HSP70 level in prefrontal cortex of rats in labetalol group was elevated (P<0.05). Significant elevation of HSP70 levels were also observed in both studied brain areas of rats in the exercise group compared with the CUMS group (P<0.01; P<0.05), and the elevation of HSP70 in hippocampus of exercise group was also higher than that of labetalol group (P<0.05). (4) The expression of iNOS in hippocampus of CUMS group was significantly higher than that of the control group (P<0.01), the iNOS levels in both brain areas of labetalol group were significantly lower than the CUMS group (both P<0.05); there were no significantly differences of iNOS levels in both brain areas of exercise group compared with the control group, while they were obviously lower than the CUMS group (both P<0.01). Conclusion (1) CUMS could lead the depressive behavior changes of rats, and aggravate the damages of the hippocampus and prefrontal cortex. (2)The aerobic exercise could improve the behavior changes and protect the function of HPA axis in CUMS animals exposed to novel acute stress obviously. And the aerobic exercise could improve the stress resistance of animals by both up-regulating the expression of HSP70 and down-regulating the expression of iNOS in hippocampus and prefrontal cortex. (3) The nonselective adrenergic receptor antagonist labetalol could improve the behavior changes partly, and protect the hippocampus and prefrontal cortex in some extent. |
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