Substance P has been extracted from brain by previously described methods and assayed on the guinea‐pig isolated ileum. The concentrations showed a wide scatter which was not due to the bioassay or to variations in the extraction procedure. Adenosines‐monophosphate and adenosine‐5″‐triphosphate have been identified in the extracts by paper chromatography and by chemical reactions. The concentrations of these substances were sufficient to interfere with the assay of substance P, adenosine‐5″‐monophosphate diminishing and adenosine‐5″‐triphosphate increasing the contractions of the ileum due to substance P. Adenosine‐5″‐diphosphate was also detected in the extracts but its biological activity was insufficient to influence the estimations. The concentrations of adrenaline, noradrenaline, potassium ions, sodium chloride, 5‐hydroxytryptamine, and γ‐aminobutyric acid were below the threshold concentrations for interference with the assay of substance P.
DOI: 10.1111/j.1476-5381.1963.tb01482.x
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