Effects of different intensities of swimming training on the expressions of protein kinase A after cerebral ischemia-reperfusion in rats

Objective To observe the effects of intensive-swimming training at different intensities on the neurological function and the expressions of protein kinase A after cerebral ischemia-reperfusion in rats,and to explore the possible neuroprotection mechanism of intensive-swimming training after cerebral ischemia-reperfusion in rats.Methods The animal model of cerebral ischemia-reperfusion was established in rats by using the intraluminal thread method to cause left middle cerebral artery occlusion (MCAO) for 2 h and then reperfusion.A total of 120 male model Sprague-Dawley rats were randomly divided into training group 1 (swimming for 5 min once a day),training group 2 (swimming for 10 min once a day),training group 3 (swimming for 20 min once a day) and control group (no training),with 30 rats in each group.Another 30 rats who were assigned to the sham-operation group were subject to no MCAO and no training.At the 3rd,7th and 14th day post operation,10 rats randomly selected from each group were examined for their neurological function by Menzies neurobehavioral test and forelimb placing test.Expressions of protein kinase A were detected by immunohistochemistry method.Expressions of PKA-mRNA were detected by using RT-PCR.Results The neurological function in sham-operation group was normal.The differences between sham-operation group and control group with regard to Menzies test and forelimb placing test scores were statistically significant at all the time points (P ＜ 0.05).The improvement of neurological function in all training groups,were significantly better than those in controls at the 3rd,7th and 14th d after swimming training,especially in training group 3 on the 14th day post-operation (P ＜0.05).At3rd,7th,and 14th days post-operation,the Menziesscores were(1.40±0.55),(1.00 ±0.71)and (0.80 ±0.45),respectively,and the forelimb placing scores were(5.20 ± 0.84),(3.80 ± 1.30) and (2.40 ± 1.14),respectively,in the training group 3.The number of positive cells and the expressions of protein kinase A mRNA were significantly higher in all training groups than those in the controls at the 3rd,7th and 14th days after swimming training,and the increase of positive cells and mRNA of PKA in the training group 3 was significantly more obvious at 14th day compared with other training groups(P ＜ 0.05).Conclusions Exercise training can increase the expression of positive cells and mRNA of PKA in rats after cerebral ischemiareperfusion,hence,it improved the injured neurological function and promote the recover of sensory and motor function,and the more intensive the training,the better the effects. Key words: Intensive training; Cerebral ischemia; Reperfusion; Protein kinases; Nerve regeneration