Denervation of Pacinian corpuscles: Electron microscopic observations in the rat following nerve transection

Nerve transection using rat sciatic nerves was employed to observe morpholo gic changes in the periodic denervation of Pacinian corpuscles. During peri ods of from 1 to 20 weeks after surgery, a total of 15 corpuscles were obta ined under the operating microscope and processed for morphologic analysis using light and electron microscopes. Based on the morphologic findings, no rmal corpuscles were composed of an axon terminal and inner and outer core cells. Following nerve transection, the axon terminal immediately disappear ed at 1 week, but the original inner and outer core cells were preserved, w ith macrophage migration occurring in the outer core. After 8 weeks, the ci rcular regularity of the inner and outer core lamellae was occasionally bro ken. The lamellae had wavy courses and there were many empty spaces in the inner core. Even at 20 weeks after denervation, there was interruption in t he continuity of the outer core cells; the membranous structure of the oute r core and the lamellar structure of the inner core were well-preserved; th e outer and inner core cells were still present. Simultaneously, a small nu mber of collagen fibrils were observed between the inner and outer core cel ls from the earliest postoperative stage. These fibrils increased in number in later stages. The results suggest that, immediately after destruction of axon terminals, macrophages migrate into the interlamellar spaces where they engulf the deb ris of the degenerated axon terminals. The degeneration of the corpuscles s eems to be similar to that of denervated nerve axons; therefore, the inner core cells, which are continuous with the Schwann cells, maintain their ori ginal condition for at least 20 weeks after corpuscle denervation. The oute r core cells, which are continuous with the perineurial nerve cells, are as sumed to be the main cells producing the collagen fibrils in the denervated Pacinian corpuscles.