CORRELATION OF RECRUITMENT ORDER WITH AXONAL CONDUCTION-VELOCITY FOR SUPRASPINALLY DRIVEN DIAPHRAGMATIC MOTOR UNITS
CORRELATION OF RECRUITMENT ORDER WITH AXONAL CONDUCTION-VELOCITY FOR SUPRASPINALLY DRIVEN DIAPHRAGMATIC MOTOR UNITS
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DOI：
10.1152/jn.1987.57.1.245
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发表时间：
1987-01-01
影响因子：
2.5
通讯作者：
BERGER, AJ
中科院分区：
文献类型：
--
作者：
DICK, TE;KONG, FJ;BERGER, AJ
在麻醉猫双电极上记录单个横隔膜运动单位(MU)的自发活动，在吸入气体中加入CO2，以轻微增强呼吸驱动(呼气末CO2<6%)。这些MU的特点是轴突传导速度(CVs)和相对起效时间(定义为开始膈神经活动后到MU开始放电的时间除以吸入时间)。运动单位轴突变异系数由传导时间和膈神经上两点之间的距离估算。比较两种实验准备的结果：一种背根完整，另一种背根横断在第四(C4)和第七(C7)颈段之间。估计的平均变异系数为46.2m/S(n=180MU)。运动单位根据其相对发病时间被分为早期和晚期招募的MU。我们将MU轴突CV与其相对募集时间相关联。对于呼吸驱动招募的横隔肌，轴突CV与相对募集时间之间存在高度显著的正相关(P<0.0001)。相关系数：完整动物r=0.70，去背根动物r=0.72，总种群r=0.72。对于成对的MU，将较早招募单位的CV与较晚招募单位的CV进行比较。在96%的完整动物和92%的背根切断动物的配对中，第一个MU的变异系数低于后来招募的MU。相对招募时间的不同与轴突简历的不同直接相关。然而，运动池中具有高轴突CV的一部分没有被采样。在本实验条件下，颈后根的传入，包括来自横隔膜受体的传入，并不影响MU的相对起效时间的分布。此外，在完整和背根切断的动物中，观察到类似比例的MU对，其中较早招募的MU具有低于较晚招募单位的CV。我们还对31对同时记录的MU进行交叉关联，以评估对膈运动神经元的共同输入。共同输入的特征是在互相关直方图(CCH)中存在宽度大于或等于3ms并且出现在触发事件的20ms内的峰。如果出现次数最多的仓位显著大于基线且相邻仓位高于基线，则判断峰值显著。(摘要截断400字)
Spontaneous activities of pairs of single diaphragmatic motor units (MUs) were recorded via two electrodes in anesthetized cats, ventilated with CO2 added to the inspired gas, which slightly enhanced respiratory drive (endtidal CO2 less than 6%). These MUs were characterized by their axonal conduction velocities (CVs) and relative onset times (defined as the time after onset of phrenic nerve activity until the MU began discharging divided by the duration of inspiration). Motor unit axonal CV was estimated by the conduction time and the distance between two points on the phrenic nerve. Results were compared from two experimental preparations: one with dorsal roots intact and the other with dorsal roots transected bilaterally between fourth (C4) and seventh (C7) cervical segments. Estimated mean CV for phrenic MUs was 46.2 m/s(n = 180 MU). Motor units were classified as early and late recruited MUs depending on their relative onset times. We correlated MU axonal CV with its relative recruitment time. A highly significant (P less than 0.0001), positive correlation between axonal CV and relative recruitment time was established for those diaphragmatic MUs recruited with this respiratory drive. Correlation coefficients were r = 0.70 for intact animals, r = 0.72 for dorsal rhizotomized animals, and r = 0.72 overall population. For pairs of MUs, the CV of the earlier recruited unit was compared with the CV of the later recruited unit. In 96% of pairs from intact animals and 92% of pairs from dorsal rhizotomized animals, the first MU had a lower CV than the MU recruited later. Difference in relative times of recruitment was directly related to difference in axonal CVs. However, a portion of the motor pool with high-axonal CVs was not sampled. Under conditions of these experiments, afferent input in cervical dorsal roots, including that from diaphragmatic receptors, did not influence the distribution of MU relative onset times. Further, a similar proportion of MU pairs wherein the earlier recruited MU had a CV lower than the later recruited unit was observed in intact and dorsal rhizotomized animals. We also cross-correlated 31 pairs of simultaneously recorded MUs to assess common input onto phrenic motoneurons. Common input was characterized by the presence of peaks having widths of greater than or equal to 3 ms in the cross-correlation histograms (CCHs) and occurring within 20 ms of the trigger event. Peaks were judged significant if the bin with the largest number of occurrences was significantly greater than base line and if neighboring bins were above base line.(ABSTRACT TRUNCATED AT 400 WORDS)