Schwann cell-induced loss of synapses in the central nervous system.

Synaptophysin immunostaining of areas of spinal gray matter occupied by radiation-induced intraspinal Schwann cells revealed a loss of immunoreactivity from the neuropil. In contrast, synaptophysin immunoreactivity was preserved on the somata and proximal dendrites of motor neurons. The present study extended these observations to the ultrastructural level and confirmed the absence not only of synapses but also of astrocytes and small- and medium-sized dendrites. These neural elements were abundant and appropriately organized in contiguous areas of irradiated neuropil not occupied by Schwann cells.