Dermatomes in the rat limbs as determined by antidromic stimulation of sensory C-fibers in spinal nerves.

Dermatomes of rats from C1 to T1 (forelimb) and from T12 to S2 (hindlimb) were determined by electrical stimulation of spinal nerves following the intravenous administration of Evans blue. After stimulation of the ventral ramus of a spinal nerve, a blue spotted area presenting the maximal innervation area of the spinal nerve appeared in the skin. Maximal innervation areas generally overlapped the adjacent areas. Each digit was innervated by two to three spinal nerves. Composite dermatomes were determined where boundary lines were defined as the midline of overlapping areas. Based on the composite dermatomes, boundary lines in the rat fore- and hindlimbs were revealed to loop around the antero-posterior axis showing a V-shaped pattern in the anterior and posterior aspects and converge to the ventral and dorsal midlines of the limb. The present dermatome chart may be applied to research concerning the segmental distribution of sensory C-fibers.