中枢去甲肾上腺素能系统对大鼠颈动脉窦反射的影响

孤离颈动脉窦,向侧脑室(LCV)注射6-羟多巴胺(6-OHDA,200μg)和电解损毁蓝斑(LC),建立窦内压(ISP)-平均动脉压(MAP)关系曲线,与对照组比较,研究中枢去甲肾上腺素能系统对ISP调节MAP的影响。通过Logistic曲线方程符合所有ISP-MAP曲线,曲线的特征是由两个参数即曲线斜率的反演点坐标和MAP变动范围决定的,MAP变动范围同斜率因子的变化率有关,并受ISP的控制。结果如下:(1)注射6-OHDA后,ISP-MAP曲线斜率变化率显著低于对照组,窦内压控制的平均动脉压变动范围明显缩小,而曲线斜率反演点的横坐标(即ISP的位置)无改变。(2)与对照组相比,电解损毁LC后,引起ISP-MAP曲线相似于注射6-OHDA后的变化,但不如后者显著。结果提示:中枢去甲肾上腺素能神经系统可易化颈动脉窦反射。

EFFECT OF THE CENTRAL NORADRENERGIC SYSTEM ON CAROTID SINUS REFLEX IN RATS

In order to study the effect of central noradrenergic system on the regulation of mean arterial pressure (MAP) by intracarotid sinus pressure (ISP), ISP-MAP relationship curves were constructed using isolated carotid sinus under the condition of injection of 6-OHDA (200 micrograms) into lateral ventricle or cauterization of locus coeruleus (LC) and compared with that obtained under the condition of control. All ISP-MAP curves can be fitted by a logistic functional plot whose characteristics can be defined by two parameters, i.e. coordinates of the inversion point of the slope of the curve and the MAP range related to the rate of change of slope factor with which carotid sinus pressure exerts its control. The results were as follows: After injection of 6-OHDA, the rate of change of the slope of the ISP-MAP curve is considerably slower than that of the normal control, thus showing a much compressed range of MAP by ISP, while the abscissa (i.e. position of ISP) of the slope inversion point of the curve shows practically no change. In comparison with the control, cauterization of LC causes a similar but less striking change of ISP-MAP curve than that of 6-OHDA injection experiment. All such differences were illustrated in Fig. 3. The above results indicated that the central noradrenergic system facilitates carotid sinus reflex and LC plays a dominant role.