Noga B R, Bras H, Jankowska E
Department of Physiology, University of Göteborg, Sweden.
Exp Brain Res. 1992;88(3):502-16. doi: 10.1007/BF00228180.
The effects of brief trains of electrical stimuli applied within the locus coeruleus and subcoeruleus, the Kölliker-Fuse nucleus and the raphe magnus, obscurus and pallidus nuclei were tested on transmission from group I and group II muscle afferent fibres in mid-lumbar spinal segments of chloralose anaesthetized cats. Changes in the effectiveness of transmission from these afferents were assessed from changes in the size of monosynaptic extracellular field potentials evoked by them. The depression of group II field potentials occurred at conditioning-testing intervals of 20-400 ms, and was maximal at intervals of 40-100 ms and 30-60 ms for potentials recorded in the intermediate zone and dorsal horn, respectively. At intervals up to about 30 ms it was combined with the depression of group I components of the intermediate zone field potentials. However, at longer intervals the conditioning stimuli depressed group II components of these potentials as selectively as monoamines applied ionophoretically at the recording site (Bras et al., 1989a, 1990). Thus, only the late depressive actions are considered as being possibly mediated by impulses in descending noradrenergic and/or serotonergic fibres. No major differences were found in the relative degree of depression of transmission from group II afferents by stimulation of the locus coeruleus/subcoeruleus, Kölliker-Fuse or raphe nuclei, either in the dorsal horn or in the intermediate zone. Since field potentials at these locations are preferentially depressed by ionophoretic application of serotonin and noradrenaline (Bras et al., 1990), and since the locus coeruleus/subcoeruleus, Kölliker-Fuse and raphe nuclei are interconnected, the study leads to the conclusion that both noradrenergic and serotonergic descending pathways can be activated by stimuli applied within either of them. Selective depression of field potentials of group II origin was also evoked by stimulation at other sites, e.g. the periaqueductal grey and medullary reticular formation, when conditioning-testing intervals were sufficiently long. Such a depression is considered to be secondary to activation of neurones of the locus coeruleus/subcoeruleus, Kölliker-Fuse or raphe nuclei and attributed to the spread of current or transsynaptic activation of these neurones, or to stimulation of their axon collaterals outside the nuclei rather than to other descending medullo-spinal systems. The non-selective depression of field potentials evoked by group I and group II afferents at shorter conditioning-testing intervals is proposed to be due to actions of reticulo-spinal pathways.
在氯醛糖麻醉的猫的腰段脊髓中部，测试了在蓝斑、蓝斑下核、 Kölliker-Fuse核以及中缝大核、中缝 obscurus 核和中缝苍白核内施加短暂电刺激串对 I 组和 II 组肌肉传入纤维传递的影响。通过这些传入纤维诱发的单突触细胞外场电位大小的变化来评估这些传入纤维传递有效性的变化。II 组场电位的抑制出现在条件刺激 - 测试刺激间隔为 20 - 400 毫秒时，分别在中间带和背角记录的电位，在间隔为 40 - 100 毫秒和 30 - 60 毫秒时抑制最大。在长达约 30 毫秒的间隔时，它与中间带场电位的 I 组成分的抑制相结合。然而，在更长的间隔时，条件刺激对这些电位的 II 组成分的抑制与在记录部位离子电泳施加单胺一样具有选择性（Bras 等人，1989a，1990）。因此，只有后期的抑制作用被认为可能是由下行去甲肾上腺素能和/或 5 - 羟色胺能纤维中的冲动介导的。通过刺激蓝斑/蓝斑下核、Kölliker-Fuse 核或中缝核，在背角或中间带，II 组传入纤维传递的相对抑制程度没有发现主要差异。由于在这些部位的场电位优先被 5 - 羟色胺和去甲肾上腺素的离子电泳施加所抑制（Bras 等人，1990），并且由于蓝斑/蓝斑下核、Kölliker-Fuse 核和中缝核相互连接，该研究得出结论，去甲肾上腺素能和 5 - 羟色胺能下行通路都可以被在它们其中任何一个内施加的刺激所激活。当条件刺激 - 测试刺激间隔足够长时，在其他部位如导水管周围灰质和延髓网状结构的刺激也能诱发 II 组起源的场电位的选择性抑制。这种抑制被认为是继发于蓝斑/蓝斑下核、Kölliker-Fuse 核或中缝核神经元的激活，并归因于这些神经元的电流扩散或跨突触激活，或者是对它们在核外的轴突侧支的刺激，而不是其他下行的延髓 - 脊髓系统。在较短的条件刺激 - 测试刺激间隔时，I 组和 II 组传入纤维诱发的场电位的非选择性抑制被认为是由于网状脊髓通路的作用。
