Aihara Y, Maeda T, Hanada K, Wakisaka S
Department of Orthodontics, Niigata University School of Dentistry, 2-5274 Gakkocho-dori, Niigata 951-8514, Japan.
Brain Res. 1999 Feb 20;819(1-2):48-57. doi: 10.1016/s0006-8993(98)01323-7.
The present study was undertaken to disclose temporal changes in the distribution of Fos-like immunoreactive (-IR) neurons in the trigeminal subnucleus caudalis (SpVc), one of the important relay nuclei for processing the nociceptive information from the oro-facial regions, following induction of experimental tooth movement in rat upper molars. Furthermore, the effect of morphine and naloxone on the levels of Fos-IR neurons in the SpVc was examined. The experimental tooth movement was induced by insertion of an elastic rubber between the first and second upper molars. In normal animals, Fos-IR neurons were rarely observed in the SpVc. Immediately after insertion of the elastic band, the distribution of Fos-IR neurons was comparable to that observed in normal animals. The number of Fos-IR neurons increased significantly from 1 to 4 h following the induction of experimental tooth movement, reaching a maximum at 2 h, and then decreasing gradually. Most of the neurons were localized in the dorsomedial portion of the superficial layers of the ipsilateral SpVc near the obex, but a few were observed at the ventral portion of the SpVc. The neurons at the superficial layers and ventral portion of the contralateral SpVc also showed Fos-like immunoreactivity, but their numbers were significantly smaller than those on the ipsilateral side. Pretreatment with morphine (3 and 10 mg/kg, i.p.) significantly reduced the induction of Fos-IR neurons at the superficial layers of the ipsilateral SpVc in a dose-dependent manner, and its effect was antagonized by the subsequent treatment of naloxone (2 mg/kg, i.p.). Naloxone pretreatment enhanced the expression of Fos-IR neurons on the ipsilateral SpVc. The present results of a reduction of Fos-IR neurons by morphine pretreatment suggest that the induction of Fos-IR neurons may be due to the noxious stimulation caused by induction of experimental tooth movement.
本研究旨在揭示大鼠上颌磨牙实验性牙齿移动后，三叉神经尾侧亚核（SpVc）中Fos样免疫反应性（-IR）神经元分布的时间变化，SpVc是处理来自口面部区域伤害性信息的重要中继核之一。此外，还研究了吗啡和纳洛酮对SpVc中Fos-IR神经元水平的影响。通过在上颌第一和第二磨牙之间插入弹性橡胶来诱导实验性牙齿移动。在正常动物中，很少在SpVc中观察到Fos-IR神经元。插入弹性带后立即观察到，Fos-IR神经元的分布与正常动物相似。实验性牙齿移动诱导后1至4小时，Fos-IR神经元数量显著增加，在2小时达到峰值，然后逐渐减少。大多数神经元位于同侧SpVc靠近闩部的浅层背内侧部分，但在SpVc腹侧部分也观察到少数神经元。对侧SpVc浅层和腹侧部分的神经元也显示出Fos样免疫反应性，但其数量明显少于同侧。吗啡（3和10mg/kg，腹腔注射）预处理以剂量依赖方式显著减少同侧SpVc浅层Fos-IR神经元的诱导，随后的纳洛酮（2mg/kg，腹腔注射）治疗可拮抗其作用。纳洛酮预处理增强同侧SpVc上Fos-IR神经元的表达。吗啡预处理使Fos-IR神经元减少的当前结果表明，Fos-IR神经元的诱导可能是由于实验性牙齿移动诱导引起的有害刺激。
