Nakamura H, Shirakawa T, Koshikawa N, Kobayashi M
Department of Pharmacology, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan Department of Pediatric Dentistry, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan.
Department of Pediatric Dentistry, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan Division of Oral and Craniomaxillofacial Research, Dental Research Center, Nihon University School of Dentistry, Chiyoda-ku, Tokyo, Japan.
J Dent Res. 2016 Feb;95(2):180-7. doi: 10.1177/0022034515611047. Epub 2015 Oct 12.
Somatosensory information from the dental pulp is processed in the primary (S1) and secondary somatosensory cortex (S2) and in the insular oral region (IOR). Stimulation of maxillary incisor and molar initially induces excitation in S2/IOR, rostrodorsal to the mandibular incisor and molar pulp-responding regions. Although S1 and S2/IOR play their own roles in nociceptive information processing, the anatomical and physiological differences in the temporal activation kinetics, dependency on stimulation intensity, and additive or summative effects of simultaneous pulpal stimulation are still unknown. This information contributes not only to understanding topographical organization but also to speculating about the roles of S1 and S2/IOR in clinical aspects of pain regulation. In vivo optical imaging enables investigation of the spatiotemporal profiles of cortical excitation with high resolution. We determined the distinct features of optical responses to nociceptive stimulation of dental pulps between S1 and S2/IOR. In comparison to S1, optical signals in S2/IOR showed a larger amplitude with a shorter rise time and a longer decay time responding to maxillary molar pulp stimulation. The latency of excitation in S2/IOR was shorter than in S1. S2/IOR exhibited a lower threshold to evoke optical responses than S1, and the peak amplitude was larger in S2/IOR than in S1. Unexpectedly, the topography of S1 that responded to maxillary and mandibular incisor and molar pulps overlapped with the most ventral sites in S1 that was densely stained with cytochrome oxidase. An additive effect was observed in both S1 and S2/IOR after simultaneous stimulation of bilateral maxillary molar pulps but not after contralateral maxillary and mandibular molar pulp stimulation. These findings suggest that S2/IOR is more sensitive for detecting dental pulp sensation and codes stimulation intensity more precisely than S1. In addition, contra- and ipsilateral dental pulp nociception converges onto spatially closed sites in S1 and S2/IOR.
来自牙髓的躯体感觉信息在初级躯体感觉皮层（S1）、次级躯体感觉皮层（S2）以及岛叶口腔区域（IOR）进行处理。对上颌切牙和磨牙的刺激最初会在S2/IOR中诱发兴奋，该区域位于下颌切牙和磨牙牙髓反应区域的嘴侧背侧。尽管S1和S2/IOR在伤害性信息处理中发挥着各自的作用，但在时间激活动力学、对刺激强度的依赖性以及同时牙髓刺激的累加或总和效应方面的解剖学和生理学差异仍然未知。这些信息不仅有助于理解拓扑组织，还有助于推测S1和S2/IOR在疼痛调节临床方面的作用。体内光学成像能够高分辨率地研究皮层兴奋的时空分布。我们确定了S1和S2/IOR之间对牙髓伤害性刺激的光学反应的不同特征。与S1相比，S2/IOR中的光学信号在对上颌磨牙牙髓刺激的反应中表现出更大的幅度、更短的上升时间和更长的衰减时间。S2/IOR中兴奋的潜伏期比S1短。S2/IOR诱发光学反应的阈值低于S1，且S2/IOR中的峰值幅度大于S1。出乎意料的是，对上下颌切牙和磨牙牙髓产生反应的S1的拓扑结构与S1中细胞色素氧化酶染色密集的最腹侧部位重叠。在双侧上颌磨牙牙髓同时刺激后，在S1和S2/IOR中均观察到累加效应，但在对侧上颌和下颌磨牙牙髓刺激后未观察到。这些发现表明，S2/IOR在检测牙髓感觉方面比S1更敏感，并且比S1更精确地编码刺激强度。此外，对侧和同侧牙髓伤害感受汇聚到S1和S2/IOR中空间上相邻的部位。
