Hu J W, Shohara E, Sessle B J
Faculty of Dentistry, University of Toronto, Ontario, Canada.
Proc Finn Dent Soc. 1992;88 Suppl 1:563-9.
In the young cat, the natural replacement of deciduous teeth with a permanent dentition may be accompanied by extensive peripheral nerve degeneration and reinnervation. Since we have previously reported significant physiological effects of tooth pulp deafferentation on V brainstem neurons, we wished to determine if deafferentation associated with deciduous tooth exfoliation was accompanied by comparable neuroplastic changes in the brainstem of kittens. We have examined the pulpal afferent terminating pattern within the brainstem as well as the electrophysiological properties of V brainstem neurons during this naturally occurring deafferentation phenomenon. The pattern of the HRP-labelled terminals in different parts of V brainstem subnuclei in kittens was similar to that in adult cats. The highest density of labelled terminals was found in the subnucleus oralis. The properties of subnucleus oralis neurons also showed many similarities between kittens at age of 3-4 months old and adult cats, e.g., (1) in the proportions of neurons activated by tactile stimulation of 1-4 teeth (mandibular and maxillary canines and premolars), (2) the ratio of neurons showing fast adapting or slow adapting responses to dental tactile stimulation, (3) the proportions of neurons activated by electrical pulp stimulation of 1-4 teeth, and (4) the minimal latencies of pulp-evoked responses. However, the incidences of pulpal inputs as well as the convergent pattern to oralis neurons of afferent inputs evoked by periodontal stimulation and electrical pulpal stimulation were less common in kittens than adult cats.
在幼猫中，乳牙自然替换为恒牙的过程可能伴随着广泛的外周神经变性和再支配。由于我们之前报道了牙髓去传入对三叉神经脑干神经元有显著的生理影响，我们希望确定与乳牙脱落相关的去传入是否伴随着小猫脑干中类似的神经可塑性变化。我们研究了在这种自然发生的去传入现象期间，牙髓传入在脑干内的终末模式以及三叉神经脑干神经元的电生理特性。幼猫三叉神经脑干亚核不同部位的HRP标记终末模式与成年猫相似。标记终末密度最高的是口亚核。3 - 4月龄幼猫和成年猫的口亚核神经元特性也有许多相似之处，例如：（1）被1 - 4颗牙齿（下颌和上颌犬齿及前磨牙）触觉刺激激活的神经元比例；（2）对牙齿触觉刺激表现出快速适应或缓慢适应反应的神经元比例；（3）被1 - 4颗牙齿牙髓电刺激激活的神经元比例；（4）牙髓诱发反应的最小潜伏期。然而，牙髓输入的发生率以及牙周刺激和牙髓电刺激诱发的传入输入对口亚核神经元的汇聚模式在幼猫中比成年猫少见。
