Fluctuations of excitability in the monosynaptic reflex pathway to lumbar motoneurons in the cat.
Fluctuations of excitability in the monosynaptic reflex pathway to lumbar motoneurons in the cat.
复制标题
猫腰部运动神经元单突触反射通路的兴奋性波动。
DOI：
10.1152/jn.1994.72.3.1227
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发表时间：
1994
影响因子：
2.5
通讯作者：
Schiff,SJ
中科院分区：
文献类型：
--
作者：
Gossard,JP;Floeter,MK;Kawai,Y;Burke,RE;Chang,T;Schiff,SJ
1.众所周知，由恒定强度的传入刺激引起的连续单突触反射（MSR）的幅度在不同的试验中会发生波动。以前的证据表明，这种兴奋性波动的运动池内可以引入前和/或突触后。使用未麻醉的去脑或去脑/脊髓猫，我们试图评估前和突触后机制的相对重要性，MSR的变异性和潜在的贡献的变化的身份响应运动神经元这种变异性。2. MSR振幅之间的比较，在切断的腹根，和发射的概率高达三个单独的运动神经元在细丝梳理从同一根，证实了运动神经元兴奋性的相关和不相关的波动参与MSR的变异性。同时从同源神经元的细胞内记录的线性回归分析表明，MSR的波动与膜电位基线的变化，以及与单突触兴奋性突触后电位峰值振幅的波动。在所有11个案例中，前者的相关性强于后者。3.刺激腓肠神经尾侧皮神经（CCS）用于改变产生小腿三头肌（GS）MSR的突触后电位背景。CCS调节和GS刺激之间的间隔选择排除了突触前抑制的参与。当通过先前的CCS刺激调节时，GS群体MSR通常（测试的8/9例）在幅度上增加，而其总体方差没有太大变化。然而，个别运动神经元，有助于人口的反应，并显示相对兴奋性和不相关的组成部分，他们的反应方差的变化。CCS条件反射后，约一半的运动神经元（6/13）的相对兴奋性降低，5/13的相对兴奋性增加，2/13的相对兴奋性无变化。单位和人口的反应比较表明，在任何给定的人口反应水平的运动神经元的身份是完全不同的CCS空调和没有。4.高频刺激Ia纤维被用来改变突触前Ia组传入神经的状态，产生群体MSR。高频刺激后强直增强并没有很大地改变人口MSR的方差或相关和不相关的波动在MSR反应的响应人口内的个别运动神经元之间的比率。然而，intratetanic抑郁症和posttetanic增强的人口MSRs伴随着显着的变化，在个人运动神经元兴奋性相对于人口的反应，再次表明，响应运动神经元的身份的变化有助于人口的反应波动。（400字处截断摘要）
1. It is well known that the amplitude of successive monosynaptic reflexes (MSR), elicited by afferent stimuli of constant strength, fluctuate from trial to trial. Previous evidence suggests that such excitability fluctuations within the motor pool can be introduced either pre- and/or postsynaptically. Using unanesthetized decerebrate or decerebrate/spinal cats, we attempted to evaluate the relative importance of pre- and postsynaptic mechanisms to MSR variability and the potential contribution of changes in the identities of responding motoneurons to such variability. 2. Comparisons between the MSR amplitude, measured in a severed ventral root, and the probability of firing of up to three individual motoneurons in fine filaments teased from the same root, confirmed that both correlated and uncorrelated fluctuations of motoneuron excitability are involved in MSR variability. Linear regression analysis from concurrent intracellular recordings from homonymous motoneurons showed that the MSR fluctuations were correlated with the variations in membrane potential baseline, as well as with the fluctuations in the monosynaptic excitatory postsynaptic potential peak amplitude. In all 11 cases tested, the former correlation was stronger than the latter. 3. Stimulation of the caudal cutaneous sural nerve (CCS) was used to alter the postsynaptic potential background on which triceps surae (GS) MSRs were generated. The interval chosen between CCS conditioning and the GS stimulation excluded the involvement of presynaptic inhibition. When conditioned by preceding CCS stimulation, GS population MSRs generally (8/9 cases tested) increased in amplitude without much change in their overall variance. However, the individual motoneurons that contributed to the population responses did show changes in both relative excitability and in the uncorrelated component of their response variance. About half of the concurrently recorded motoneurons (6/13) showed a decrease in relative excitability after CCS conditioning, 5/13 showed an increase, and 2/13 were unchanged. Comparison of unit and population responses indicated that the identities of the motoneurons that responded at any given level of population response were quite different with and without CCS conditioning. 4. High-frequency stimulation of Ia fibers was used to alter the state of presynaptic Group Ia-afferents that produced population MSRs. Post tetanic potentiation following high-frequency stimulation did not greatly alter the variance of population MSRs or ratio of correlated and uncorrelated fluctuations in MSR responses among individual motoneurons within the responding population. However, intratetanic depression and posttetanic potentiation of population MSRs were accompanied by marked shifts in individual motoneuron excitability relative to the population response, again indicated that changes in the identities of responding motoneurons contributes to population response fluctuations.(ABSTRACT TRUNCATED AT 400 WORDS)