Department of Physiology and Neuroscience, Sahlgrenska Academy, University of Gothenburg, Göteborg, Sweden.
J Neurophysiol. 2011 Apr;105(4):1581-93. doi: 10.1152/jn.00712.2010. Epub 2011 Jan 27.
It has previously been established that ventral spinocerebellar tract (VSCT) neurons and dorsal spinocerebellar tract neurons located in Clarke's column (CC DSCT neurons) forward information on actions of premotor interneurons in reflex pathways from muscle afferents on α-motoneurons. Whether DSCT neurons located in the dorsal horn (dh DSCT neurons) and spinocervical tract (SCT) neurons are involved in forwarding similar feedback information has not yet been investigated. The aim of the present study was therefore to examine the input from premotor interneurons to these neurons. Electrical stimuli were applied within major hindlimb motor nuclei to activate axon-collaterals of interneurons projecting to these nuclei, and intracellular records were obtained from dh DSCT and SCT neurons. Direct actions of the stimulated interneurons were differentiated from indirect actions by latencies of postsynaptic potentials evoked by intraspinal stimuli and by the absence or presence of temporal facilitation. Direct actions of premotor interneurons were found in a smaller proportion of dh DSCT than of CC DSCT neurons. However, they were evoked by both excitatory and inhibitory interneurons, whereas only inhibitory premotor interneurons were previously found to affect CC DSCT neurons [as indicated by monosynaptic excitatory postsynaptic potentials (EPSPs) and inhibitory postsynaptic potentials (IPSPs) in dh DSCT and only IPSPs in CC DSCT neurons]. No effects of premotor interneurons were found in SCT neurons, since monosynaptic EPSPs or IPSPs were only evoked in them by stimuli applied outside motor nuclei. The study thus reveals a considerable differentiation of feedback information provided by different populations of ascending tract neurons.
先前已经证实，位于 Clarke 柱（CC DSCT 神经元）内的腹侧脊髓小脑束（VSCT）神经元和背侧脊髓小脑束神经元将来自肌肉传入纤维的反射途径中前运动神经元的信息传递到α运动神经元。位于背角（dh DSCT 神经元）内的背侧脊髓小脑束神经元和脊髓颈束（SCT）神经元是否参与传递类似的反馈信息尚未得到研究。因此，本研究的目的是研究前运动神经元对这些神经元的输入。在主要的后肢运动核内施加电刺激，以激活投射到这些核的中间神经元的轴突侧支，并从 dh DSCT 和 SCT 神经元中获得细胞内记录。通过脊髓内刺激诱发的突触后电位的潜伏期以及时间易化的有无来区分刺激中间神经元的直接作用和间接作用。在 dh DSCT 神经元中，前运动神经元的直接作用比 CC DSCT 神经元中的少。然而，它们被兴奋性和抑制性中间神经元激活，而先前只发现抑制性前运动神经元影响 CC DSCT 神经元[如 dh DSCT 神经元中的单突触兴奋性突触后电位（EPSP）和抑制性突触后电位（IPSP）以及 CC DSCT 神经元中的仅 IPSP 所示]。在 SCT 神经元中没有发现前运动神经元的作用，因为只有在运动核外施加刺激时，它们才能在 SCT 神经元中诱发单突触 EPSP 或 IPSP。因此，该研究揭示了不同上行束神经元提供的反馈信息的相当大的分化。
