Presynaptic inhibition, EPSP amplitude, and motor-unit type in triceps surae motoneurons in the cat.
Presynaptic inhibition, EPSP amplitude, and motor-unit type in triceps surae motoneurons in the cat.
复制标题
猫小腿三头肌运动神经元的突触前抑制、EPSP 振幅和运动单位类型。
DOI：
10.1152/jn.1983.49.4.922
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发表时间：
1983
影响因子：
2.5
通讯作者：
Munson,JB
中科院分区：
文献类型：
--
作者：
Zengel,JE;Reid,SA;Sypert,GW;Munson,JB
1.在巴比妥酸盐麻醉猫的小腿三头肌运动神经元上记录了刺激异源神经产生的复合Ia组兴奋性突触后电位（EPSP）。测量运动神经元的基强度、输入电阻和轴突传导速度，并根据肌肉单位的机械反应对运动单位进行分类。2.在33个腓肠肌内侧运动神经元上记录到的EPSPs幅值为0.6 ~ 4.3mV。平均EPSP振幅在主要MG运动单位类型之间存在差异，按快收缩、快疲劳（FF）;快收缩、抗疲劳（FR）;慢收缩、抗疲劳（S）（FF小于FR小于S）的顺序增加。15个比目鱼肌运动神经元记录到的EPSP幅度为0.3 ~ 3.4mV，平均1.4mV。3.在后二头肌-半腱肌（PBST）神经中，通过一系列条件性齐射产生了EPSP的突触前抑制。在33个MG细胞中，PBST条件刺激使EPSP的幅度降低11- 50%，平均抑制27%。15个比目鱼肌运动神经元的EPSPs幅度降低5- 84%，平均抑制37%。4.当突触前抑制的幅度表示为抑制百分比时，突触前抑制与运动单位类型或EPSP的幅度之间没有关系。然而，当突触前抑制被表示为抑制的毫伏的绝对量时，抑制的幅度与整个小腿三头肌群体（MG、外侧腓肠肌、比目鱼肌）以及每个肌肉群体内的EPSP振幅高度相关。这种相关性在MG FF和FR运动单位人群中也很显著。5.我们的结论是，EPSP的幅度，而不是运动单位类型是突触前抑制的大小的主要决定因素。然而，由于运动单位类型对EPSP振幅的影响，净效应是突触前抑制的增加顺序为FF小于FR小于S。
1. Composite group Ia excitatory postsynaptic potentials (EPSPs) produced by heteronymous nerve stimulation were recorded from triceps surae motoneurons of barbiturate-anesthetized cats. Motoneuron rheobase, input resistance, and axonal conduction velocity were measured, and motor units were classified on the basis of the mechanical responses of their muscle units. 2. The amplitude of EPSPs recorded from 33 medial gastrocnemius (MG) motoneurons ranged from 0.6 to 4.3 mV. The mean EPSP amplitude differed among the major MG motor-unit types, increasing in the order fast twitch, fast fatiguing (FF); fast twitch, fatigue resistant (FR); slow twitch, fatigue resistant (S) (FF less than FR less than S). The amplitude of EPSPs recorded from 15 soleus motoneurons ranged from 0.3 to 3.4 mV, with a mean of 1.4 mV. 3. Presynaptic inhibition of EPSPs was produced by trains of conditioning volleys in the posterior biceps-semitendinosus (PBST) nerve. In 33 MG cells PBST conditioning stimulation reduced the amplitude of EPSPs by 11-50%, with a mean inhibition of 27%. The amplitude of EPSPs in 15 soleus motoneurons was decreased by 5-84%, with a mean inhibition of 37%. 4. When the magnitude of presynaptic inhibition was expressed as percent inhibition, there was no relation between presynaptic inhibition and either motor-unit type or the amplitude of the EPSP. However, when presynaptic inhibition was expressed as the absolute amount of inhibition in millivolts, the magnitude of inhibition was highly correlated with EPSP amplitude both across the entire triceps surae population (MG, lateral gastrocnemius, soleus) as well as within each muscle population. This correlation was also significant within the MG FF and FR motor-unit populations. 5. We conclude that EPSP amplitude and not motor-unit type is the major determinant of the magnitude of presynaptic inhibition. However, because of the effect of motor-unit type on EPSP amplitude, the net effect is that presynaptic inhibition increases in the order FF less than FR less than S.