Alstermark B, Sasaki S
Exp Brain Res. 1985;59(2):353-64. doi: 10.1007/BF00230915.
The effect of corticospinal volleys evoked by stimulation of the contralateral pyramid was investigated using intracellular recordings from alpha-motoneurones to forelimb muscles. Confirming and extending previous observations (Illert et al. 1977, Illert and Wiedemann 1984), short latency EPSPs within a disynaptic range were evoked by a train of pyramidal volleys in all varieties of shoulder, elbow, wrist and digit motoneurones. The amplitude of pyramidal EPSPs was sensitive to the stimulus repetition rate. Maximal amplitudes were observed around 2-4 Hz, while at 10 Hz the early EPSP was markedly reduced and the long latency EPSP abolished. The persistence of disynaptic EPSPs after a corticospinal transection in C5/C6 suggested that, for all types of forelimb motor nuclei, disynaptic EPSPs are relayed by C3-C4 propiospinal neurones (PNs) (c.f. Illert et al. 1977). The transection, however, caused a clear reduction in the EPSP of all motoneurone types. After a ventral lesion of the lateral funicle in C5/C6 interrupting the axons of the C3-C4 PNs, disynaptic (and possibly trisynaptic) EPSPs were evoked by a short train of pyramidal volleys. It is postulated that intercalated neurones in a disynaptic cortico-motoneuronal pathway also exist in the forelimb segments. Disynaptic pyramidal IPSPs were observed in most types of forelimb motor nuclei both before and after a corticospinal transection in C5/C6. At all joints, pyramidal excitation dominated in motoneurones to physiological flexors, while in extensor motoneurones mixed excitation and inhibition or dominant inhibition was common. Comparison of pyramidal effects in slow motoneurones (classified according to the after-hyperpolarization duration) to the long head of the triceps and anconeus revealed dominant excitation in the former and inhibition in the latter. It is suggested that the slow motor units in these muscles differ in their function although both muscles are elbow extensors.
利用对前肢肌肉α运动神经元的细胞内记录，研究了刺激对侧锥体所诱发的皮质脊髓冲动的效应。证实并扩展了先前的观察结果（Illert等人，1977年；Illert和Wiedemann，1984年），在所有类型的肩部、肘部、腕部和手指运动神经元中，一串锥体冲动可诱发突触范围内的短潜伏期兴奋性突触后电位（EPSP）。锥体EPSP的幅度对刺激重复率敏感。在2 - 4Hz左右观察到最大幅度，而在10Hz时，早期EPSP明显减小，长潜伏期EPSP消失。C5/C6水平皮质脊髓横断后双突触EPSP持续存在，这表明对于所有类型的前肢运动核，双突触EPSP由C3 - C4脊髓 propriospinal神经元（PNs）中继（参见Illert等人，1977年）。然而，横断导致所有运动神经元类型的EPSP明显减小。在C5/C6水平对侧索进行腹侧损伤，中断C3 - C4 PNs的轴突后，一串短的锥体冲动可诱发双突触（可能还有三突触）EPSP。据推测，在前肢节段中也存在双突触皮质 - 运动神经元通路中的插入神经元。在C5/C6水平皮质脊髓横断前后，在大多数类型的前肢运动核中都观察到了双突触锥体抑制性突触后电位（IPSP）。在所有关节处，锥体兴奋在生理屈肌的运动神经元中占主导，而在伸肌运动神经元中，混合兴奋和抑制或主导抑制很常见。比较对三头肌长头和肘肌的慢运动神经元（根据超极化后持续时间分类）的锥体效应，发现前者以兴奋为主，后者以抑制为主。提示这些肌肉中的慢运动单位功能不同，尽管两者都是肘部伸肌。
