Noga B R, Jankowska E, Skoog B
Department of Physiology, University of Manitoba, Winnipeg, Canada.
Exp Brain Res. 1995;105(1):25-38. doi: 10.1007/BF00242179.
The effects of short trains of electrical stimuli applied within the cuneiform nucleus and the subcuneiform region were examined on transmission from group I and group II muscle afferents to first-order spinal neurons. Variations in the effectiveness of transmission from these afferents were assessed from changes in the sizes of the monosynaptic component of extracellular field potentials evoked following stimulation of muscle nerves. Field potentials evoked from group II muscle afferents in the dorsal horn of the midlumbar and sacral segments and in the intermediate zone of the midlumbar segments were reduced when the test stimuli applied to peripheral nerves were preceded by conditioning stimulation of the cuneiform nucleus or the subcuneiform region. The depression occurred at conditioning-testing intervals of 20-400 ms, being maximal at intervals of 32-72 ms for dorsal horn potentials and 40-100 ms for intermediate zone potentials. At the shortest intervals, both group II and group I field potentials in the intermediate zone were depressed. Conditioning stimulation of the cuneiform nucleus depressed group II field potentials nearly as effectively as conditioning stimulation of the coerulear or raphe nuclei. We propose that the nonselective depression of transmission from group I and II afferents at short intervals is due to the activation of reticulospinal pathways by cells or fibers stimulated within the cuneiform area. We also propose that the selective depression of transmission from group II afferents at long intervals is mediated at least partly by monoaminergic pathways, in view of the similarity of the effects of conditioning stimulation of the cuneiform nucleus and of the brainstem monoaminergic nuclei and by directly applied monoamines (Bras et al. 1990). In addition, it might be caused by primary afferent depolarization mediated by non-monoaminergic fibers (Riddell et al. 1992).
研究了在楔状核和楔状下区域内施加短串电刺激对I组和II组肌肉传入纤维至一级脊髓神经元的传递的影响。通过刺激肌肉神经后诱发的细胞外场电位单突触成分大小的变化，评估这些传入纤维传递效率的变化。当对周围神经施加测试刺激之前，先对楔状核或楔状下区域进行条件刺激时，在腰中部和骶段背角以及腰中部中间带由II组肌肉传入纤维诱发的场电位会降低。这种抑制发生在条件刺激-测试刺激间隔为20 - 400毫秒时，对于背角电位，在32 - 72毫秒间隔时最大，对于中间带电位，在40 - 100毫秒间隔时最大。在最短间隔时，中间带的II组和I组场电位均受到抑制。楔状核的条件刺激对II组场电位的抑制效果几乎与蓝斑核或中缝核的条件刺激相同。我们提出，在短间隔时I组和II组传入纤维传递的非选择性抑制是由于楔状区域内受刺激的细胞或纤维激活了网状脊髓通路所致。我们还提出，鉴于楔状核和脑干单胺能核的条件刺激效果与直接应用单胺的效果相似（Bras等人，1990年），在长间隔时II组传入纤维传递的选择性抑制至少部分是由单胺能通路介导的。此外，它可能是由非单胺能纤维介导的初级传入去极化引起的（Riddell等人，1992年）。
