Neuromedin U-like immunoreactivity in rat intestine: regional distribution and immunohistochemical study

Neuromedin U-25 and its C-terminal octapeptide, neuromedin U-8 are related peptides originally identified in porcine brain which elicit potent uterus stimulant activity. Radioimmunoassay using an antiserum raised against porcine neuromedin U-8, indicated that neuromedin U-like immunoreactivity in the rat was far more abundant in the small intestine than the brain. Neuromedin U in the rat is a single, a 23 amino acid peptide (2, 17). Rat neuromedin U has the same 7 residues on its C-terminus as porcine neuromedin U, and the antiserum against porcine neuromedin U-8 is 100% crossreactive with rat neuromedin U. Immunohistochemical analyses using this antiserum revealed that neuromedin U-immunoreactive structures in rat intestine were confined to the enteric nervous system, implying that neuromedin U may be involved in neuronal regulation of gut function.