Nociceptin-like immunoreactivity in autonomic nuclei of the rat spinal cord

Immunohistochemical techniques were used to localize nociceptin-like immunoreactivity (NOCI-LI) in the rat spinal cords. NOCI-LI nerve fibers were distributed in three fairly well-defined regions: superficial layers of the dorsal horn, central canal area, and intermediolateral cell column (ILp) of lower cervical, thoracic, upper lumbar, and sacral segments of the spinal cord. A few NOCI-LI somata of small diameter were noted in the dorsal horn; NOCI-LI cell bodies were infrequently observed in the ILp or ventral horn. Concentration of NOCI-LI in nerve fibers of the superficial layers and in fibers projecting into the spinal sympathetic and parasympathetic nuclei suggests that the peptide may participate in sensory as well as autonomic functions. (C) 1997 Elsevier Science Ireland Ltd.