Cold Blockade of Axonal Transport Activates Premitotic Activity of Schwann Cells and Wallerian Degeneration

Abstract

Between 3 and 4 days after transection of cat sciatic nerve, Schwann cell-associated premitotic activity spreads anterogradely along degenerating distal nerve stumps at a rate of approximately 200 mm/day. We inves- tigated whether fast anterograde axonal transport contrib- utes to the initiation of this component of Wallenan de- generation. Axonal transport was blocked in intact and transected cat sciatic nerves by focally chilling a proximal segment to temperatures below 11“C for 24 hr. Incorpora- tion of t3H]thymidine(a marker of premitotic DNA syn- thesis) was then measured 3 and 4 days posttransection in cold blocked- and control-degenerating nerves. Effects of cold block prior to and concomitant with nerve transectionwere studied. Results failed to support the hypothesis that Schwann-cell premitotic activity after axotomy is asso- ciatedwithentryintotheaxonofmitogenicsubstancesand their anterograde fast transport along the distal stump. In- stead, data suggested that progressive anterograde failure of fast anterograde transport distal to transection serves to effect the Schwann-cell premitotic response to axotomy. Key Words: Peripheral nerve-Axonal transport- Schwann cell-Wallerian degeneration-Cold block. Oak- lander A. L. and Spencer P. S. Cold blockade of axonal transport activates premitotic activity of Schwann cells and Wallerian degeneration