Innervation of the spinal cord by sympathetic fibers

Pharmacologic and neurochemical studies suggest that catecholamines are still present below the level of transection in the spinal cord of the chronic spinal animal, despite the degeneration of bulbospinal catecholamine pathways. Histofluorescence studies of rat and dog spinal cord revealed noradrenergic fibers and varicosities remaining in the chronically decentralized spinal cord which can account for the low concentrations of norepinephrine (NE) found below the transection. The fibers appear to enter the spinal cord with blood vessels through the anterior median fissure, and are probably of sympathetic origin. In the spinal cord, these fibers can dissociate from blood vessels and continue through the neuropil; they are associated with neurons in the ventral horn and occasionally in the central gray. These peripheral sympathetic fibers may influence motor systems and other nervous functions.