Baker L L, Chandler S H
Department of Physical Therapy, University of Southern California, Los Angeles 90242.
Brain Res. 1987 Sep 15;420(2):340-50. doi: 10.1016/0006-8993(87)91255-8.
The purpose of this study was to characterize the changes in postsynaptic potentials recorded in ankle extensor motoneurons resulting from activation of the sural nerve after spinal cord transection in the adult cat. Eight acute and nine chronic animals were spinalized at T12. Intracellular recordings from motoneurons innervating the triceps surae were performed. Sural nerve stimulation evoked complex synaptic potentials consisting of early and late components in all motoneurons. Early excitatory and inhibitory postsynaptic potentials (PSPs), as well as long latency excitatory postsynaptic potentials were recorded and averaged for assessment of PSP amplitude and duration. Early PSPs, both excitatory and inhibitory, were significantly larger in the motoneurons of cats spinalized 4-6 months earlier. Central latency of excitatory potentials were similar in the two samples of motoneurons, but the central latency associated with the initial inhibitory PSP was significantly shorter in the recordings from motoneurons of chronic spinal cats. In most recordings, an additional inhibitory PSP followed the initial excitatory PSP in motoneurons, and this secondary inhibitory PSP was similar in peak amplitude and duration in both samples of motoneurons. Also, a long latency excitatory PSP was recorded in a large percentage of motoneurons from both samples. This potential was typically of greater amplitude and longer duration in the motoneurons from chronic animals, when compared to recordings from acute animals. Although changes in amplitude and duration of PSP activity could be documented, there was no marked alteration in the frequency of occurrence of each PSP pattern recorded from the two preparations. This suggests that the synaptic pathways mediating the sural nerve reflexes have not qualitatively changed in the chronic spinal animal. The changes in amplitudes and durations of the PSPs in the chronic spinal cat indicate, however, that quantitative changes have occurred. The quantitative changes have probably occurred in the interneuronal networks activated by cutaneous nerve (sural) stimulation, since it was shown that only minor changes in motoneuron membrane properties could be recorded in these same chronic spinal animals.
本研究的目的是描述成年猫脊髓横断后，腓肠神经激活引起的踝伸肌运动神经元突触后电位的变化。8只急性和9只慢性动物在T12水平进行脊髓横断。对支配腓肠三头肌的运动神经元进行细胞内记录。腓肠神经刺激在所有运动神经元中诱发了由早期和晚期成分组成的复杂突触电位。记录早期兴奋性和抑制性突触后电位（PSP）以及长潜伏期兴奋性突触后电位，并进行平均以评估PSP的幅度和持续时间。早期兴奋性和抑制性PSP在4 - 6个月前脊髓横断的猫的运动神经元中明显更大。两个运动神经元样本中兴奋性电位的中枢潜伏期相似，但慢性脊髓猫运动神经元记录中与初始抑制性PSP相关的中枢潜伏期明显更短。在大多数记录中，运动神经元的初始兴奋性PSP之后会跟随一个额外的抑制性PSP，并且这个继发性抑制性PSP在两个运动神经元样本中的峰值幅度和持续时间相似。此外，在两个样本的大部分运动神经元中都记录到了长潜伏期兴奋性PSP。与急性动物的记录相比，慢性动物运动神经元中的这种电位通常幅度更大、持续时间更长。尽管可以记录到PSP活动的幅度和持续时间的变化，但从两种制剂记录的每种PSP模式的发生频率没有明显改变。这表明在慢性脊髓动物中，介导腓肠神经反射的突触通路在性质上没有改变。然而，慢性脊髓猫中PSP的幅度和持续时间的变化表明发生了定量变化。定量变化可能发生在由皮神经（腓肠神经）刺激激活的中间神经元网络中，因为已表明在这些相同的慢性脊髓动物中，运动神经元膜特性仅发生了微小变化。
