title: Unmyelinated and small myelinated axons in rat ventral roots.
abstract: 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.
mesh_terms: D000818:Animals; D001369:Axons / Q000648:ultrastructure*; D009412:Nerve Fibers / Q000648:ultrastructure*; D009413:Nerve Fibers, Myelinated / Q000648:ultrastructure*; D051381:Rats; D012583:Schwann Cells / Q000648:ultrastructure; D013126:Spinal Nerve Roots / Q000648:ultrastructure*