腺苷对家兔颈动脉体化学感受器活动的影响

EFFECT OF ADENOSINE ON CAROTID CHEMORECEPTOR ACTIVITY IN THE RABBIT

在39只乌拉坦麻醉家兔,记录了腺苷作用于颈动脉体时窦神经化学感受性传入单位的放电活动。全部实验中共记录了73个有自发放电的化学感受性单位。所得结果如下:(1)颈动脉内注射腺苷(10ug/kg)时,在55个单位中有51个的放电频率由0.76±0.10增加到1.53±0.23 imp/s(P<0.001),部分实验中有新的单位被激活。(2)在隔离的颈动脉窦灌流液中加入腺苷(0.5,1.0、5.0、10、50和100μg/kg)时,9个单位的放电频率由0.51±0.06分别增加到0.58±0.07、0.78±0.13、0.96±0.15、1.11±0.017、1.34±0.21和1.38±0.18imp/s,有明显的剂量依赖性(P<0.001).(3)9个自发放电频率为1.30±0.40 imp/s 的单位,在颈动脉内注射多巴胺(50μg/kg)后,其放电频率减慢至0.56±0.19imp/s(P<0.001)。在多巴胺作用的基础上再注射腺苷。可使放电频率增加到1.07±0.28imp/s,但与注射多巴胺前的腺苷效应相比,此增值明显减小(P<0.001)。根据以上结果,我们推测腺苷对颈动脉体化学感受器的兴奋作用,可能与其作用于感受器复合体的突触前膜,从而使颈动脉体内抑制性递质多巴胺释放减少,以及腺苷直接兴奋化学感受性神经末梢有关。

The response of single carotid chemoreceptor afferent fibers upon adenosineacting on the carotid body(CB)was examined in 39 urethan-anesthetized rabbits.Totally 73 units with spontaneous discharge were recorded in our experiment.The results were as follows:(1)Of 55 units,51 showed an increase in dischargefrequency from 0.76±0.10 to 1.53±0.23 imp/s.A few new units were re-cruited concomitantly in response to intracarofid injection of adenosine(10μg/kg).(2)Adding adenosine in the doses of 0.5,1.5,10,50 and 100 μg/kg tothe perfusate passing through the isolated carotid sinus led to dose-dependentincrease in the discharge from 0.51±0.06 to 0.58±0.07,0.78±0.13,0.96±0.15,1.11±0.17,1.34±0.21 and 1.38±0.18 imp/s,respectively(P<0.001,n=9 units).(3)In other 9 units with spontaneous discharge rate of 1.30±0.40imp/s,the activity was decreased to 0.56±0.19 imp/s(P<0.01)by intracaro-tid injection of dopamine(50μg/kg).Intracarotid injection of adenosine tothe CB pretreated with dopamine still activated the units with an increase in firingrate to 1.07±0.28 imp/s(P<0.01).However,the increment was less pro-minent as compared with that of adenosine administration before dopamineinjection(P<0.001).From the results obtained,it is hypothesized that theexciting effect of adenosine on the CB chemoreceptor may be attributed to its ac-tion on the presynaptic component of the chemoreceptor complex in attenuatingthe release of inhibitory transmitter dopamine,and its direct stimulating actionon the chemosensory nerve endings.