Distribution and localization of neuromedin B-like immunoreactivity in pig, cat and rat spinal cord

The distribution and localization of neuromedin B, a novel bombesin-like decapeptide isolated from porcine spinal cord, was investigated by newly established radioimmunoassay and immunocytochemistry in the pig, cat and rat spinal cord. Neuromedin B-like immunoreactivity was found to be concentrated particularly in the dorsal part of lumbosacral segments in all species studied and the highest concentration of immunoreactivity was 25.7 +/- 3.4 pmol/g wet wt in the dorsal part of sacral region of pig spinal cord. The nature of the immunoreactivity was studied by gel permeation and high pressure liquid chromatography. Chromatography of spinal cord extracts from three species revealed two major peaks of neuromedin B-like immunoreactivity and the prevalent molecular from co-eluted with synthetic porcine neuromedin B. Immunocytochemistry localized neuromedin B immunoreactivity to fibres and terminals throughout the entire length of the spinal cord of pig, cat and rat. Fibres were most abundant in laminae I and II of the dorsal horn, the area around the central canal (lamina X) and intermediolateral cell columns of thoracic and sacral segments. In lumbosacral segments neuromedin B-immunoreactive fibres were slightly more numerous, in both dorsal and ventral spinal cord, than in cervical and thoracic regions.