Substance P occurs in nerve fibers of the central and peripheral nervous system and in endocrine cells of the gut. It stimulates smooth muscle contraction, gives rise to vasodilation and is involved in sensory functions. Substance P-containing tumors arising in the ileum are often associated with the carcinoid syndrome, characterized by flushing of the skin, diarrhea, broncho-constriction and sudden drops in blood pressure. Substance P is commonly found in the midgut carcinoids and some of the symptoms may be related to this peptide.
Absorption with 10 – 100 µg SP and NKA per ml diluted antiserum abolishes the staining while GRP and NKB do not.
Positive control: Frozen sections of rat colon