Sanders K H, Zimmermann M
J Neurophysiol. 1986 Apr;55(4):644-59. doi: 10.1152/jn.1986.55.4.644.
In the glabrous skin of the rat's hindfoot the same triple set of low-threshold mechanoreceptors is present as has been found in other mammals: slowly adapting (SA), rapidly adapting (RA), and very rapidly adapting Pacinian corpuscle-like (PC) receptors. Their functional characteristics were examined in normal rats and compared with those of sensitive mechanoreceptors found in the glabrous skin of the foot 2-24 wk after crush of the plantar nerves, resulting in regeneration of the transected nerve fibers. After 2 wk of nerve regeneration, low-threshold RA and SA cutaneous mechanoreceptors reappeared in the foot skin. Responses of PC receptors were recorded again after 3 wk, at which time the proportion of fibers that could be identified as low-threshold cutaneous mechanoreceptors had regained control level. Discharge patterns of regenerated cutaneous mechanosensitive receptors were very similar to those of normal skin mechanoreceptors. Their sensitivity to controlled mechanical stimulation was, however, still reduced 4 wk after the lesion. After 8 wk RA and SA receptors had regained their normal dynamic sensitivity, i.e., the responsiveness to the velocity of skin indentation. The static sensitivity of SA receptors, i.e., responsiveness to maintained skin indentation, was not consistently reestablished within 24 wk. No shift in sensitivity could be deduced from tuning curves of PC receptors examined 3-24 wk after nerve crush. In addition to the low-threshold mechanoreceptors, high-threshold (HT) mechanoreceptive fibers were found in controls and in animals with regenerating nerves. This type of fiber was most frequently found 1 wk after the nerve crush, when reinnervation of the foot started. They probably represent fibers not connected to specific mechanoreceptor end organs. Thus, functional restitution of the highly specific cutaneous mechanoreceptors occurs fairly soon after invasion of the original territory by the regenerating nerve. It is assumed that the underlying mechanism is the rapid reconnection of fibers with the end organs that have either survived during the period of denervation or regenerated subsequent to reinnervation of the skin.
在大鼠后足的无毛皮肤上，存在着与其他哺乳动物中发现的相同的三组低阈值机械感受器：慢适应（SA）、快适应（RA）和非常快适应的类帕西尼小体（PC）感受器。在正常大鼠中检测了它们的功能特性，并与足底神经挤压2 - 24周后足部无毛皮肤中发现的敏感机械感受器的特性进行了比较，这导致横断的神经纤维发生再生。神经再生2周后，足部皮肤中重新出现了低阈值的RA和SA皮肤机械感受器。3周后再次记录PC感受器的反应，此时可被识别为低阈值皮肤机械感受器的纤维比例已恢复到对照水平。再生的皮肤机械敏感感受器的放电模式与正常皮肤机械感受器的非常相似。然而，损伤4周后，它们对受控机械刺激的敏感性仍然降低。8周后，RA和SA感受器恢复了正常的动态敏感性，即对皮肤压痕速度的反应性。SA感受器的静态敏感性，即对持续皮肤压痕的反应性，在24周内未能始终如一地恢复。从神经挤压后3 - 24周检查的PC感受器的调谐曲线中无法推断出敏感性的变化。除了低阈值机械感受器外，在对照动物和神经再生的动物中还发现了高阈值（HT）机械感受纤维。这种纤维在神经挤压1周后最常出现，此时足部开始重新神经支配。它们可能代表未与特定机械感受器终末器官相连的纤维。因此，高度特异性的皮肤机械感受器在再生神经侵入原始区域后不久就会发生功能恢复。据推测，其潜在机制是纤维与在去神经支配期间存活或在皮肤重新神经支配后再生的终末器官迅速重新连接。
