DENTAL PAIN: STUDIES ON TRIGEMINAL NUCLEUS CAUDALIS

该项目旨在首次确定 最近发现的一种途径的特征， 是一种特殊的疼痛途径 尾侧亚核（Subnucleus caudalis，SNC）是核团的主要部位。 参与处理疼痛信息的三叉神经感觉复合体 产生于口面区域并传递到丘脑。 主要 腹后内侧核（VPM）是SNC的投射部位 以及位于更内侧的板内核。 据信 疼痛的感觉辨别方面在VPM中处理， 丘脑内侧区的动机情感成分。 然而，在这方面， 很少有研究调查内侧丘脑在疼痛中的作用 尽管其与临床疼痛状态的潜在相关性。 最近的解剖学研究描述了一个迄今未知的途径 起源于SNC边缘层，中继于中央下核 (Sm)位于丘脑内侧，终止于眶腹外侧（VLO） 皮层 间接证据有力地表明，这一途径涉及 特别是疼痛信号的处理和传递。 没有生理 研究已经解决了这一潜在的非常重要的途径。 的 建议的电生理实验将研究功能 这条路的性质。 将微电极置于VLO皮质， Sm和SNC的麻醉猫，并用于逆向刺激SNC 投射到Sm的神经元和投射到VLO皮质的Sm神经元。 这些SNC和Sm投射神经元的功能特性将 通过施加各种伤害性和非伤害性的 对口面部区域的机械、热和电刺激 包括牙髓。 SNC神经元的形态及其与周围神经元的关系 SNC内的位置将通过细胞内注射 辣根过氧化物酶 刺激下行通路的效果 起源于大脑皮层、中脑导水管周围灰质和中缝大核， 将研究SNC神经元的反应。 的结果予以 这些研究将有助于我们了解 口腔面部区域的牙痛和其它疼痛状况， 可能导致改善临床方法来控制疼痛。

This project aims to determine, for the first time, the functional characteristics of a recently discovered pathway which has been proposed to be a specific pain pathway. Subnucleus caudalis (SNC) is the major site in the trigeminal sensory complex involved in processing pain information arising in the orofacial region and in relaying it to thalamus. The main thalamic projection sites of SNC are the ventroposteromedial nucleus (VPM) and the more medially located intralaminar nuclei. It is believed that the sensory-discriminative aspects of pain are processed in VPM and the motivational-affective components in medial regions of thalamus. However, few studies have investigated the role of the medial thalamus in pain processing in spite of its potential relevance to clinical pain states. Recent anatomical studies have described a hitherto unknown pathway originating in the marginal layer of SNC, relaying in nucleus submedius (Sm) in medial thalamus and terminating in the ventrolateral orbital (VLO) cortex. Indirect evidence strongly suggests that this pathway is involved specifically in processing and relay of pain signals. No physiological studies have addressed this potentially very important pathway. The proposed electrophysiological experiments will study the functional properties of this pathway. Microelectrodes will be placed in VLO cortex, Sm and SNC of anesthetized cats and used to antidromically stimulate SNC neurons which project to Sm and Sm neurons which project to VLO cortex. The functional characteristics of these SNC and Sm projection neurons will be determined by applying various nociceptive and nonnociceptive mechanical, thermal and electrical stimuli to the orofacial region including the tooth pulp. The morphology of the SNC neurons and their location within SNC will be determined by intracellular injection of horseradish peroxidase. The effect of stimulating descending pathways originating in the cortex, periaqueductal gray and raphe magnus on the responses of SNC neurons will be investigated. The results of these studies will contribute to our understanding of the mechanisms involved in dental pain and other painful conditions of the orofacial region and may possibly lead to improved clinical methods for the control of pain.