Alstermark B, Lundberg A, Sasaki S
Exp Brain Res. 1984;56(2):293-307. doi: 10.1007/BF00236285.
Intracellular recording was made in the C3-C4 segments from cell bodies of a previously described system of propriospinal neurones (PNs), which receive convergent monosynaptic excitation from different higher motor centres and mediate disynaptic excitation and inhibition from them to forelimb motoneurones. Inhibitory effects in these PNs have now been investigated with electrical stimulation of higher motor centres and forelimb nerves. Short-latency IPSPs were evoked by volleys in the cortico-, rubro- and tectospinal tracts and from the reticular formation. Latency measurements showed that those IPSPs which required temporal summation were disynaptically mediated. After transection of the corticospinal tract in C2, only small and infrequent disynaptic IPSPs were evoked from the pyramid. It is postulated that disynaptic pyramidal IPSPs only to a small extent are evoked by monosynaptic excitation of reticulospinal inhibitory neurones known to project directly to the PNs, and that they are mainly mediated by inhibitory interneurones in the C3-C4 segments. Tests with spatial facilitation revealed monosynaptic excitatory convergence from tecto-, rubro- and probably also from reticulospinal fibres on inhibitory interneurones monosynaptically excited from corticospinal fibres (interneuronal system I). Disynaptic IPSPs were also evoked in the great majority of the PNs by volleys in forelimb muscle and skin nerves. A short train of volleys was usually required to evoke these IPSPs from group I muscle afferents. In the case of cutaneous nerves and mixed nerves single volleys were often effective, and the lack of temporal facilitation of IPSPs produced by a train of volleys showed strong linkage from these nerves. The results obtained after transection of the dorsal column at different levels show that the relay is almost entirely rostral to the forelimb segments. Test with spatial facilitation revealed that interneurones monosynaptically activated from forelimb afferents receive convergent excitation from corticospinal but not or only weakly so from tecto- or rubrospinal fibres. There was also convergence from group I muscle afferents and low threshold cutaneous afferents on common interneurones. It is postulated that the disynaptic IPSPs from forelimb afferents are mediated by inhibitory interneurones (interneuronal system II) other than those receiving convergent descending excitation. Volleys in corticospinal fibres, in addition to the disynaptic IPSPs, evoke late IPSPs in the PNs. Similar late IPSPs were evoked from the ipsilateral forelimb by stimulation of the FRA.(ABSTRACT TRUNCATED AT 400 WORDS)
在C3 - C4节段，对先前描述的脊髓固有神经元（PNs）系统的细胞体进行细胞内记录。这些脊髓固有神经元接受来自不同高级运动中枢的汇聚单突触兴奋，并介导从这些中枢到前肢运动神经元的双突触兴奋和抑制。现在已经用电刺激高级运动中枢和前肢神经来研究这些PNs中的抑制作用。皮质脊髓束、红核脊髓束和顶盖脊髓束以及网状结构的冲动可诱发短潜伏期抑制性突触后电位（IPSPs）。潜伏期测量表明，那些需要时间总和的IPSPs是由双突触介导的。在C2水平切断皮质脊髓束后，仅从锥体束诱发小的且不频繁的双突触IPSPs。据推测，双突触锥体束IPSPs仅在小程度上由已知直接投射到PNs的网状脊髓抑制性神经元的单突触兴奋诱发，并且它们主要由C3 - C4节段中的抑制性中间神经元介导。空间易化测试显示，来自顶盖脊髓束、红核脊髓束以及可能还有网状脊髓纤维的单突触兴奋性汇聚到由皮质脊髓纤维单突触兴奋的抑制性中间神经元上（中间神经元系统I）。前肢肌肉和皮肤神经的冲动在绝大多数PNs中也诱发双突触IPSPs。通常需要一串短的冲动才能从I组肌肉传入纤维诱发这些IPSPs。对于皮肤神经和混合神经，单个冲动通常有效，并且一串冲动产生的IPSPs缺乏时间易化表明这些神经有很强的联系。在不同水平切断背柱后获得的结果表明，中继几乎完全在前肢节段的头侧。空间易化测试显示，由前肢传入纤维单突触激活的中间神经元接受来自皮质脊髓束的汇聚兴奋，但不接受或仅微弱接受来自顶盖脊髓束或红核脊髓束纤维的兴奋。I组肌肉传入纤维和低阈值皮肤传入纤维也汇聚到共同的中间神经元上。据推测，来自前肢传入纤维的双突触IPSPs由不同于接受汇聚下行兴奋的抑制性中间神经元（中间神经元系统II）介导。皮质脊髓纤维的冲动除了诱发双突触IPSPs外，还在PNs中诱发晚期IPSPs。通过刺激FRA，同侧前肢也诱发类似的晚期IPSPs。（摘要截短于400字）
