Unmyelinated and small myelinated axons in rat ventral roots

J Comp Neurol. 1977 May 1;173(1):175-84. doi: 10.1002/cne.901730110.


The present study is an analysis of the ventral roots in the rat. The smallest myelinated fibers are found in segments T1-L2 and L6-S1. These fibers are regarded as preganglionic efferents and the L6-S1 outflow is more cranial than the sacral parasympathetic outflow in other animals. Large numbers of unmyelinated axons are seen in segments T1-L2 and L6-S1, the same segments that contain the smallest myelinated fibers. This data will be used as a baseline for determining the functional categories of the unmyelinated axons.

Publication types

  • Research Support, U.S. Gov't, P.H.S.

MeSH terms

  • Animals
  • Axons / ultrastructure*
  • Nerve Fibers / ultrastructure*
  • Nerve Fibers, Myelinated / ultrastructure*
  • Rats
  • Schwann Cells / ultrastructure
  • Spinal Nerve Roots / ultrastructure*