Inflammatory peptide in spinal cord: evidence that the mediator of antidromic vasodilatation is not substance P.

Extracts from rat and bovine spinal cord were found to have 300-1000 times more cutaneous oedema-inducing activity than could be attributed to their substance P-like activity estimated by assay on guinea-pig ileum. The activity on both assay systems was reduced in cord extracts from rats pretreated as neonates with capsaicin. Results of assays of fractions obtained from gel-filtration chromatography indicated that an agent, in the molecular size range for peptides, was present in spinal cord extracts, which possessed some of the properties of substance P but was not identical to it.