Okada Nobuo, Matsumoto Norio, Kitada Yasuyuki
Department of Operative Dentistry and Endodontics, School of Dentistry, Iwate Medical University, Morioka, Iwate 020-8505, Japan.
Arch Oral Biol. 2002 Dec;47(12):815-29. doi: 10.1016/s0003-9969(02)00118-8.
The effect of conditioning stimulation of the internal capsule on nociceptive neurones in the rat diencephalon was investigated. The animals were anaesthetised with N(2)O/O(2) (2:1) and 0.5% halothane, and immobilised with pancuronium bromide. Nociceptive neurones responding to noxious stimulation of the face and oral structures were recorded in the ventral posteromedial nucleus, posterior group and zona incerta. These neurones were classified into wide dynamic range and nociceptive-specific types. Functional segregation of these nociceptive neurones was not apparent within the nucleus or between nuclei. A test stimulus with a single rectangular pulse (5-70 V) was applied to the centre of the receptive field; the nociceptive neurones exhibited short- and/or long-latency responses. Both responses in about 45% of the nociceptive neurones were inhibited by conditioning stimuli to the contralateral internal capsule with trains of 33 pulses (300 microA) at 330 Hz. The percent inhibitory effects on the nociceptive neurones of each area were 68.0+/-14.8% (n = 6) in the ventral posteromedial nucleus, 72.8+/-12.4% (n = 4) in the posterior group and 61.5+/-7.5% (n = 4) in the zona incerta. Effective sites for conditioning stimulation were concentrated in the lateral side of the internal capsule, through which the corticofugal fibres from the somatosensory cortex pass. These findings suggest that the transmission of nociceptive information to the diencephalon is modulated by stimulation of the internal capsule at the level of the trigeminal sensory complex in the brainstem. They might provide a novel way to elucidate the neurophysiological basis for antinociception by stimulation of the internal capsule observed in clinical studies.
研究了内囊条件刺激对大鼠间脑伤害性神经元的影响。动物用N₂O/O₂（2:1）和0.5%氟烷麻醉，并用泮库溴铵固定。在腹后内侧核、后组和未定带记录对脸部和口腔结构有害刺激产生反应的伤害性神经元。这些神经元分为广动力范围型和伤害性特异型。这些伤害性神经元在核内或核间未表现出明显的功能分离。用单个矩形脉冲（5 - 70V）的测试刺激施加于感受野中心；伤害性神经元表现出短潜伏期和/或长潜伏期反应。约45%的伤害性神经元的两种反应都被以330Hz的33个脉冲（300μA）串对侧内囊的条件刺激所抑制。对每个区域伤害性神经元的抑制作用百分比在腹后内侧核为68.0±14.8%（n = 6），在后组为72.8±12.4%（n = 4），在未定带为61.5±7.5%（n = 4）。条件刺激的有效部位集中在内囊外侧，体感皮层的皮质离心纤维通过此处。这些发现表明，在脑干三叉神经感觉复合体水平，内囊刺激可调节伤害性信息向间脑的传递。它们可能为阐明临床研究中观察到的内囊刺激抗伤害感受的神经生理基础提供一种新方法。
