Lundberg A, Malmgren K, Schomburg E D
Exp Brain Res. 1987;65(2):282-93. doi: 10.1007/BF00236300.
The convergence of group II muscle afferents on interneurones in reflex pathways has been elucidated by investigating interaction in transmission to motoneurones. Recording was also made from interneurones activated from group II afferents. Maximal group II EPSPs evoked in motoneurones from different muscles (extensors or flexors and extensors) did not summate linearly but with a deficit of 35-40%. The corresponding deficit in summation with Ia EPSPs was 7%. It is suggested that the difference in deficit is caused largely by occlusion due to shared interneuronal discharge zones and that it gives an approximate minimal measure of the convergence of group II afferents from different muscles on the interneurones. Tests with weak group II volleys from different muscles gave no or little evidence for spatial facilitation in the disynaptic excitatory pathway to flexor motoneurones, and there was no or little temporal facilitation of transmission in this pathway. It is suggested that group II excitation of the interneurones in this pathway depends on few afferents giving large unitary EPSPs. Convergence of cutaneous afferents and joint afferents on the interneurones was evidenced by spatial facilitation from these afferents of group II transmission to motoneurones. Convergence on interneurones in the trisynaptic inhibitory pathway from group II afferents to extensor motoneurones was also investigated with the spatial facilitation technique. There was convergence on common interneurones of group II afferents from different muscles (extensors or flexors and extensors) and from cutaneous afferents as well as joint afferents. Trisynaptic group II IPSPs, including those depending on spatial facilitation from different muscles were resistant to recurrent depression from motor axon collaterals and are therefore not mediated by the reciprocal Ia inhibitory pathway. Interneurones with monosynaptic group II EPSPs were recorded from in the dorsal horn and intermediate region. Graded stimulation revealed large unitary EPSPs from few group II afferents. The EPSP evoked by a single group II afferent may produce firing (extracellular recording). Convergence of monosynaptic group II EPSPs from different muscles was rather limited but could be from flexors and extensors. Extensive multisensory convergence onto some of these interneurones was indicated by di- or polysynaptic EPSPs from group II and III muscle afferents, from joint afferents and from cutaneous afferents.(ABSTRACT TRUNCATED AT 400 WORDS)
通过研究向运动神经元的传递相互作用，已阐明了II类肌传入纤维在反射通路中与中间神经元的汇聚情况。也对由II类传入纤维激活的中间神经元进行了记录。在来自不同肌肉（伸肌或屈肌与伸肌）的运动神经元中诱发的最大II类兴奋性突触后电位（EPSP）并非线性总和，而是有35% - 40%的亏缺。与Ia类EPSP总和时相应的亏缺为7%。有人提出，亏缺差异很大程度上是由于共享中间神经元放电区导致的阻塞所致，并且它给出了来自不同肌肉的II类传入纤维在中间神经元上汇聚的大致最小量度。用来自不同肌肉的弱II类冲动进行测试，未发现或几乎未发现向屈肌运动神经元的双突触兴奋性通路中有空间易化现象，并且该通路中也没有或几乎没有传递的时间易化现象。有人提出，该通路中中间神经元的II类兴奋取决于少数能产生大的单突触EPSP的传入纤维。皮肤传入纤维和关节传入纤维在中间神经元上的汇聚通过这些传入纤维对II类向运动神经元传递的空间易化得以证明。还用空间易化技术研究了从II类传入纤维到伸肌运动神经元的三突触抑制通路中中间神经元的汇聚情况。来自不同肌肉（伸肌或屈肌与伸肌）、皮肤传入纤维以及关节传入纤维的II类传入纤维在共同的中间神经元上存在汇聚。包括那些依赖于不同肌肉空间易化的三突触II类抑制性突触后电位（IPSP）对运动轴突侧支的反复抑制有抗性，因此不是由相互的Ia类抑制通路介导的。在背角和中间区域记录到了具有单突触II类EPSP的中间神经元。分级刺激显示少数II类传入纤维能产生大的单突触EPSP。单个II类传入纤维诱发的EPSP可能会引发放电（细胞外记录）。来自不同肌肉的单突触II类EPSP的汇聚相当有限，但可能来自屈肌和伸肌。来自II类和III类肌传入纤维、关节传入纤维以及皮肤传入纤维的双突触或多突触EPSP表明，这些中间神经元存在广泛的多感觉汇聚。（摘要截取自400词）
