Changes of heart rate variability and impairment of learning and memory induced by cerebral ischemia/reperfusion in rats / 生理学报

The present study was designed to observe the influence of cerebral ischemia/reperfusion injury on learning and memory in hyperlipidemic rats and estimate the changes of activity of autonomic nervous system. Twenty-three male Wistar rats were randomly divided into three groups, named control group (C group, n=10), hyperlipidemia group (H group, n=6) and hyperlipidemia-ischemia group (HI group, n=7), respectively. The rats in H and HI group were fed a high-fat diet for 2 weeks and the rats in all groups were examined through Morris water maze (MWM) task. The rats in HI group underwent ischemia/reperfusion by 2-vessel occlusion (2-VO) method, and had electrocardiogram (ECG) recording simultaneously. The MWM task and ECG recording were taken again after 7 d of recuperation. The following results were obtained: (1) In the second place navigation performance and probe trial performance, the frequency of memory in quadrant of hidden-platform and memory score decreased significantly in HI group compared to that in C and H groups. (2) The heart rate in HI group decreased slowly after ischemia; the power at high frequency band (HF) reduced gradually, meanwhile the power at middle frequency band (MF) and the ratio of power at MF and HF decreased clearly compared to baseline value. (3) After 7 d of ischemia/reperfusion, the heart rate in HI group was significantly higher than that in H group (P<0.05). While there was no statistical change in the power at MF, the power at HF decreased and the ratio of MF/HF increased significantly (P<0.05). The data demonstrated that ischemia/reperfusion decreased the activity of autonomic nervous system, and the reduction of sympathetic nerve activity was much more than that of vagus nerve activity. The results suggest that the hippocampus neuron injury caused by ischemia induces cognitive disorder and imbalance of vago-sympathetic nerve activity accompanied by vagus nerve suppression.

Effects of beta-cypermethrin on voltage-gated potassium channels in rat hippocampal CA3 neurons / 生理学报

The effects of beta-cypermethrin (consisting of alpha-cypermethrin and theta-cypermethrin) on the transient outward potassium current (I(A)) and delayed rectifier potassium current (I(K)) in freshly dissociated hippocampal CA3 neurons of rats were studied using whole-cell patch-clamp technique. The results indicated that alpha-cypermethrin increased the value of I(A) and theta-cypermethrin decreased the value of I(A), though both of them shifted steady activation curve of I(A) towards negative potential. theta-cypermethrin contributed to the inactivation of I(A). The results also showed that alpha-cypermethrin and theta-cypermethrin decreased the value of I(K), and shifted the steady state activation curve of I(K) towards negative potential. Both alpha-cypermethrin and theta-cypermethrin had no obvious effects on the inactivation of I(K). theta-cypermethrin prolonged recovery process of I(K). These results imply that both transient outward potassium channels and delayed rectified potassium channels are the targets of beta-cypermethrin, which may explain the mechanism of toxical effects of beta-cypermethrin on mammalian neurons.