The fate of the axon and its terminal in the Pacinian corpuscle following sciatic nerve section

Abstract

Central nerve fibres of Pacinian corpuscles of the cat were examined by semiserial sections 2, 3, 4, 5, 6 and 9 days after sciatic nerve cut. Axons of the Pacinian corpuscles showed degenerative changes 4 days after transsection and the removal of axonal and myelin debris was almost completed within 9 days. Axonal degeneration was characterized by disintegration of filaments and tubules, disruption of axolemma, swelling of mitochondria and loss of filopod processes in the terminal axon. Selective preservation of filaments in local areas of terminal axons was found in some corpuscles. The myelinated portions of the nerve fibre were removed by Schwann cells and the unmyelinated terminal portions by inner core lamellar cells. Mitochondria and other degenerated axoplasmic organelles of the terminal axon formed dense bodies following their engulfment by lamellar cells. The unmyelinated portion of the axon was removed faster than the myelinated. The rate of removal of axonal debris varied along the length of both the unmyelinated and myelinated portions of the nerve fibre. Similarity in the behaviour and morphology of reactive lamellar and Schwann cells points to the possibility of the common derivation of these cells.