中枢交感神经活性抑制对老年大鼠心肌细胞收缩功能的影响

目的探讨中枢交感神经活性抑制对老年大鼠心功能、单个心室肌细胞收缩幅度和细胞存活率的影响。方法选择月龄>18个月的SD大鼠30只,随机分为老年可乐定组和老年对照组,每组15只,另选4~6月龄的SD大鼠18只为成年组,老年可乐定组大鼠以可乐定腹腔注射2周,其他2组用生理盐水腹腔注射2周,进行血流动力学参数测定,酶分离大鼠心肌细胞,用含不同浓度钙离子或异丙肾上腺素(ISO)的KH液对心肌细胞进行表面灌流,观察心肌细胞的收缩幅度,计算其存活率。结果与成年组大鼠比较,老年对照组左心室压力最大上升和下降速率(±dp/dtmax)降低,左心室舒张末压(LVEDP)升高,且心肌细胞在不同浓度钙离子或ISO刺激下收缩幅度较成年组降低(P<0.05)。老年可乐定组大鼠±dp/dtmax改善,LVEDP降低,心肌细胞在同等条件刺激下收缩幅度较老年对照组增加(P<0.05);3组大鼠间细胞存活率无统计学差异(P>0.05)。结论抑制中枢交感神经紧张性可改善老年大鼠心功能,增加心肌细胞的收缩幅度。

Effects of inhibition of sympathetic activity on Ventricular myocytes contractile function in aged rats

Objective To investigate the effects of inhibition of central sympathetic activity by clonidine on single ventricular myocyte contractile amplitude,heart function and survival rate of myocytes in aged rats.Methods Normal adult and aged rats were used.The aged rats were randomly divided into two groups,aged control group and aged clonidine group.After injection of clonidine and saline for two weeks in clonidine group and control group respectively,hemodynamic parameters were measured for ±dp/dtmax and left ventricular end-diastolic pressure(LVEDP)in all the rats.Then,the hearts were excised,isolated into single ventricular myocyte.The survival rates of myocytes were measured,and cardiomyocyte contractile amplitude was measured using stimulation by KH solutions containing different concentrations of calcium or isoproterenol(ISO).Results ±dp/dtmax was significantly lower and LVEDP was higher in the aged rats than adult rats(P<0.05).Compared with aged control rats,injection of clonidine for two weeks significantly decreased the LEVDP(P<0.05)and increased ±dp/dtmax(P<0.05).It also increased the ventricular myocyte contractile amplitude after stimutation by different concentrations of calcium or ISO.Conclusions Inhibition of central sympathetic tone by clonidine can increase single ventricular myocyte contractile amplitude and improve heart function in aged rats.