Amino-acid Sequence of Substance P

IN 1931 von Euler and Gaddum¹, studying the tissue distribution of acetylcholine, found that brain and intestine contained a substance that stimulated contraction of the isolated rabbit jejunum and caused transient hypotension when injected intravenously into anaesthetized rabbits. These effects could not be ascribed to acetylcholine, for they were not prevented by the previous administration of atropine. The initial studies were made on crude acid alcohol extracts of equine brain and intestine, dried in powder form. The active principle in the preparation was later referred to as substance P (P for powder) and this non-committal term subsequently achieved widespread acceptance in the literature, in the absence of any clearly definable biological role for the compound (or compounds) involved.