Rectospinal neurons: evidence for a direct projection from the enteric to the central nervous system in the rat.

Wheat germ agglutinin-horseradish peroxidase conjugate (WGA-HRP), horseradish peroxidase (HRP), and Fluorogold injections were made into the spinal cord segments L4-S2, and HRP was applied to cut L6 and S1 dorsal roots in the rat. These procedures resulted in retrograde labeling of neuronal cell bodies in the rectal wall. Labeled neurons were found both inside and outside myenteric ganglia. Their occurrence was restricted to 5 mm proximal of the external anal sphincter. These cell bodies might represent an additional type of afferent neuron, furnishing a direct information pathway from the rectal wall to the spinal cord.