Ultrastructural changes in dendrites of central neurons during axon reaction.

Retrograde atrophy of rat thalamus is marked by the appearance of profound alterations in dendrites. Concurrently, similar changes occur in parent cell somata. Electron-dense and abnormally electron-lucent dendritic profiles appear and are removed over different time courses. The morphologic features of the abnormal dendrites are detailed. Electron-dense and electron-lucent dendritic profiles are not observed in cat red nucleus after rubrospinal tractotomy. Rather, neurofilamentous hyperplasia and proliferation of smooth endoplasmic reticulum appear in affected dendrites and are identical to changes observable at the same time in the reacting parent nerve cells. The literature is reviewed and discussion is developed on the similarities of perikaryal and dendritic changes that occur in axon reaction and transneuronal degeneration.