Study On Effects And Mechanisms Of Low Temperature On Neurobehavioral Function In Mice

ObjectiveTo study effects and biochemistry and molecule mechanisms of low temperature on neurobehavioral function of mice,and to provide ways of prevention and cure of low temperature damage.Methods1.240 mice that were bolted by the test of Y model maze from 300 mice were randomly divided into 3 groups of A,B and C with different cold exposure time and 3 control groups[(25±2)℃].Each group had 40 mice.After low-temperature[(4±0.5)℃]test,the functions of motion and anti-fatigue in 20 mice randomly selected from each group were measured.The function of learning and memory of the rest of 20 mice were measured.2.120 mice that were bolted by the test of Y model maze from 200 mice were randomly divided into 3 groups of A,B and C with different cold exposure time and 3 control groups[(25±2)℃].Each group had 20 mice.After low-temperature[(4±0.5)℃]test,the 10 mice randomly selected from each group were rapidly decollated to fetch the brains to prepare of brain tissue bomogenate and determine of endothelium material,lipid peroxidation and activities of ATPaps of brain tissue.The rest of 10 mice in each group were rapidly decollated to fetch hippocampus to determine gene expression of bax,bcl-2 and c-fos.Results1.Effects of low temperature on function of learning and memory Compared with control group,in the test of learning,the total electric shock period,the total electric times,and the error reaction times of mice in group A and group C were increased significantly(P＜0.01,P＜0.05),but the rate of right reaction were decreased significantly(P＜0.01,P＜0.05).In the test of memory ability,the total electric shock period of mice in group A and group C were increased significantly(P＜0.01,P＜0.05), the rate of right reaction were decreased significantly(P＜0.05).2.Effects of low temperature on the function of motion and anti-fatigue Compared with control group,in swimming test,the swimming time of mice in group A and group C were shortened obviously(P＜0.01,P＜0.05).The plasma concentration of BS decreased significantly,the plasma concentrations of BUN and LD increased significantly,the plasma activity of CK increased significantly(P＜0.01, P＜0.05).3.Change of biochemical indicators of brain tissue Group A and group C compared with control group,the level of endothelin(ET) and angiotensinⅡ(AgⅡ) in brain tissue increased significantly,the level of nitrogen monoxidum(NO) in brain tissue decreased significantly(P＜0.01,P＜0.05),the activity of superoxide dismutase(SOD) and the level of glutathion(GSH) in brain tissue decreased significantly,and the level of malonaldehyde(MDA) in brain tissue increased significantly(P＜0.01,P＜0.05).4.Change of gene expression of bax,bcl-2 and c-fos in hippocampus tissue Group A and group C compared with control group,expression of bax in hippocampus tissue increased significantly,the number of positive cells increased and dyeing of positive cells were deepened significantly(P＜0.01).The number of positive cells of bcl-2 increased also,but the rate of bcl-2/bax were decreased significantly (P＜0.05).Expression of c-fos in hippocampus tissue increased significantly,the number of positive cells increased and dyeing of positive cells were deepened significantly(P<0.01).Conclusions1.Low temperature may cause the total electric shock period,the total electric times, and the error reaction times of mice increase,the rate of right reaction decrease. Therefore low temperature may decrease the function of learning and memory.2.Low temperature may cause the swimming time shorten,the plasma concentration of BS decrease,the plasma concentrations of BUN and LD increase and the plasma activity of CK increased.Then low temperature may cause energy substances decrease and metabolic substances increase.So low temperature may decrease the function of motion and anti-fatigue.3.Low temperature may also cause vascular endothelial substances,lipid peroxidation substances,activities of ATP ase in brain tissue change.The change of humoral factor may be biochemical mechanisms that low temperatue decreases neurobehavioral function.4.Low temperature may cause expression bax in hippocampus tissue increase,the rate of bcl-2/bax decrease,expression of c-fos in hippocampus tissue increase. Abnomal expression of these genes may be the molecular mechanisms that low temperature decreases the function of learning and memory.