Kwan C L, Hu J W, Sessle B J
Faculty of Dentistry, University of Toronto, Ontario, Canada.
Somatosens Mot Res. 1993;10(2):115-31. doi: 10.3109/08990229309028828.
The effects of tooth pulp deafferentation on brainstem neuronal properties were examined in the rat trigeminal (V) subnucleus oralis. Deafferentation was produced by removal of the coronal tooth pulp of all left mandibular molars. Neurons in the subnucleus oralis were then electrophysiologically characterized in chloralose/urethane-anesthetized rats at a single postoperative time. The mechanoreceptive field and response properties of low-threshold mechanoreceptive (LTM) neurons in rats studied at postoperative times of 3-4 days, 7-13 days, and 28-40 days were compared to those in control (unoperated) rats. Functional changes in oralis LTM neurons were observed in all tooth-pulp-deafferented rats, but most statistically significant changes were apparent only at the 7- to 13-day postoperative period. In 7- to 13-day pulp-deafferented rats, there was a significant increase in the incidence of neurons with a two-divisional mechanoreceptive field, accompanied by a significant decrease in the incidence of neurons with a maxillary mechanoreceptive field. This group of rats also showed a significant increase in the incidence of neurons with a mechanoreceptive field involving both mandibular and maxillary divisions. For neurons that could be activated by light mechanical stimulation of one or more mandibular or maxillary teeth, the 7- to 13-day pulp-deafferented rats showed a significant increase in the incidence of neurons with such periodontal mechanosensitive inputs involving both mandibular and maxillary divisions. There was also a significant increase in the incidence of spontaneously active neurons in this group of rats. For neurons with a mechanoreceptive field involving mystacial vibrissae, there was a significant increase in all three groups of pulp-deafferented rats in the maximal width of the vibrissal row (i.e., the number of vibrissae in the longest horizontal row of vibrissae, stimulation of which was effective in activating a given neuron). No significant differences were found between groups in the incidence of neurons with a mandibular mechanoreceptive field or in the proportions of neurons with a mechanoreceptive field located in each of several defined orofacial regions. There was also no significant difference between groups in the mean latency to electrical stimulation of the neuronal mechanoreceptive field, or in the proportions of rapidly adapting (RA) and slowly adapting (SA) neurons. These results show many similarities with the functional changes of oralis LTM neurons in the cat following tooth pulp deafferentation, and indicate that the rat may serve as a very useful model for V brainstem neuroplasticity induced by tooth pulp deafferentation.
在大鼠三叉神经（V）口侧亚核中研究了牙髓去传入对脑干神经元特性的影响。通过去除所有左侧下颌磨牙的冠状牙髓来产生去传入。然后在术后单个时间点，对水合氯醛/乌拉坦麻醉的大鼠口侧亚核中的神经元进行电生理特性分析。将术后3 - 4天、7 - 13天和28 - 40天研究的大鼠中低阈值机械感受性（LTM）神经元的机械感受野和反应特性与对照（未手术）大鼠进行比较。在所有牙髓去传入的大鼠中均观察到口侧LTM神经元的功能变化，但大多数具有统计学意义的变化仅在术后7至13天明显。在术后7至13天牙髓去传入的大鼠中，具有双分区机械感受野的神经元发生率显著增加，同时具有上颌机械感受野的神经元发生率显著降低。这组大鼠还显示，具有涉及下颌和上颌分区的机械感受野的神经元发生率显著增加。对于可以通过对一颗或多颗下颌或上颌牙齿进行轻度机械刺激而激活的神经元，术后7至13天牙髓去传入的大鼠中，具有涉及下颌和上颌分区的这种牙周机械敏感输入的神经元发生率显著增加。这组大鼠中自发活动神经元的发生率也显著增加。对于具有涉及触须的机械感受野的神经元，在所有三组牙髓去传入的大鼠中，触须排的最大宽度（即最长水平触须排中的触须数量，刺激这些触须可有效激活给定神经元）均显著增加。在具有下颌机械感受野的神经元发生率或位于几个定义的口面部区域中每个区域的具有机械感受野的神经元比例方面，各组之间未发现显著差异。在对神经元机械感受野进行电刺激的平均潜伏期，或快速适应（RA）和缓慢适应（SA）神经元的比例方面，各组之间也没有显著差异。这些结果显示出与猫牙髓去传入后口侧LTM神经元的功能变化有许多相似之处，并表明大鼠可能是牙髓去传入诱导的V脑干神经可塑性的非常有用的模型。
