Hamm T M, Koehler W, Stuart D G, Vanden Noven S
J Physiol. 1985 Dec;369:379-98. doi: 10.1113/jphysiol.1985.sp015908.
In anaesthetized low-spinal cats, intracellular recordings were made of the Ia excitatory post-synaptic potential (e.p.s.p.) responses of semimembranosus motoneurones to electrical stimulation (Group I range) of nerve branches supplying the anterior and posterior heads of semimembranosus, the anterior and posterior parts of biceps femoris, and the distal part of semitendinosus. Recordings were also made during stimulation of nerves to the gracilis muscle and to the vasti muscle group. Stimulation of the semimembranosus-anterior nerve branch produced Ia e.p.s.p.s. of greater amplitude in semimembranosus-anterior motoneurones than in semimembranosus-posterior cells; likewise, stimulation of the semimembranosus-posterior nerve branch produced larger e.p.s.p.s. in cells which supplied the posterior head than in those which supplied the anterior head. Stimulation of the nerve branches to components of two 'flexor' muscles (Sherrington, 1910), biceps-posterior and semitendinosus-distal, produced larger e.p.s.p.s in semimembranosus-posterior cells than in the anterior motoneurones. A tendency was found for stimulation of the nerve to biceps femoris-anterior (an 'extensor') to produce larger e.p.s.p.s in semimembranosus-anterior than in-posterior motoneurones. However, this effect was of borderline (0.06 greater than P greater than 0.05) significance. The limited monosynaptic input produced by stimulation of the nerves to the gracilis and vasti muscles showed that their Ia axons do not distinguish between the two semimembranosus cell groups. A slight topographic organization of motoneurones within the semimembranosus motor nucleus was found, with anterior cells encountered, on average, at a more rostral level of the spinal cord than posterior cells. A similar topographic arrangement was observed in the rostrocaudal distribution of Group I afferent fibres in the dorsal roots and motor axons from the two sets of motoneurones in the ventral roots. These findings are consistent with 'location specificity' (Scott & Mendell, 1976) being a factor which contributes to the observed pattern of homonymous Ia connexions. A role for 'species specificity' (Scott & Mendell, 1976) in determining the observed pattern of homonymous Ia connexions was indicated by species-dependent differences in e.p.s.p. amplitude in pairs of semimembranosus-anterior and -posterior motoneurones at similar rostrocaudal locations in the spinal cord. The pattern of heteronymous connexions to the semimembranosus motor nucleus also showed evidence for species specificity. However, no clear topographic pattern was evident in these connexions.
在麻醉的低位脊髓猫中，对半膜肌运动神经元的Ia兴奋性突触后电位（e.p.s.p.）进行细胞内记录，该电位是半膜肌运动神经元对供应半膜肌前后头、股二头肌前后部以及半腱肌远端的神经分支进行电刺激（I组范围）时产生的。同时也记录了刺激支配股薄肌和股四头肌群的神经时的情况。刺激半膜肌前神经分支时，半膜肌前运动神经元产生的Ia e.p.s.p.s.幅度大于半膜肌后运动神经元；同样，刺激半膜肌后神经分支时，支配后半部的细胞产生的e.p.s.p.s.大于支配前半部的细胞。刺激两条“屈肌”（谢灵顿，1910）即股二头肌后部和半腱肌远端的神经分支时，半膜肌后细胞产生的e.p.s.p.s.大于前运动神经元。发现刺激股二头肌前部（“伸肌”）神经时，半膜肌前运动神经元产生的e.p.s.p.s.大于后半运动神经元，但这种效应具有临界显著性（0.06＞P＞0.05）。刺激支配股薄肌和股四头肌的神经所产生的有限单突触输入表明，它们的Ia轴突无法区分半膜肌的两个细胞群。在半膜肌运动核内发现运动神经元存在轻微的拓扑组织，平均而言，前细胞位于脊髓比后细胞更靠前的水平。在背根中I组传入纤维的 rostrocaudal 分布以及腹根中两组运动神经元的运动轴突中也观察到类似的拓扑排列。这些发现与“位置特异性”（斯科特和门德尔，1976）是导致观察到的同名Ia连接模式的一个因素相一致。脊髓中相似 rostrocaudal 位置的半膜肌前运动神经元和后运动神经元对中，e.p.s.p.幅度的物种依赖性差异表明“物种特异性”（斯科特和门德尔，1976）在决定观察到的同名Ia连接模式中起作用。与半膜肌运动核的异名连接模式也显示出物种特异性的证据。然而，在这些连接中没有明显的拓扑模式。
