Immunocytochemical demonstration of serotonergic cells, terminals and axons in the spinal cord of the stingray, Dasyatis sabina.

Serotonin-like immunoreactivity, as demonstrated by the PAP method, was contained within cells as well as fibers and terminals, in the spinal cord of the stingray. Serotonergic spinal neurons were seen on 43% of the sections examined and were restricted to the ventral white matter. Immunoreactive terminals and varicosities were densely distributed over the spinal gray matter at all segmental levels, and stained fibers were seen in all portions of the white matter with the exception of the medial anterior and dorsal funiculi.