Crude substance P from brain contains a cholecystokinin-like peptide.
The subfractions Fa, Fb, and Fc of crude substance P (SP) preparations made from human and bovine brains were analysed for SP and the COOH-terminal octapeptide of cholecystokinin (CCK-8). The  methods were specific radioimmunoassays (RIAs) for SP and CCK-8, and bioassays on isolated organs of the guinea pig: the ileum, the gallbladder and the field-stimulated vas deferens. 1. In bioassays of synthetic peptides the vas deferens reacted specifically to SP and the gallbladder to CCK-8. 2. RIAs and bioassays revealed unequivocally that most of SP-like activity was present in Fb, while Fc contained mainly CCK-8-like activity. Varying results were obtained with Fa. 3. The pharmacologically active principle of Fc is CCK-8 or a closely related peptide. Earlier results concerning the pharmacological and neurochemical properties of Fc must be ascribed to this peptide.
D000818:Animals; D001923:Brain Chemistry; D055598:Chemical Phenomena; D002621:Chemistry; D002766:Cholecystokinin / Q000032:analysis*; D006168:Guinea Pigs; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects; D010455:Peptides / Q000032:analysis* / Q000494:pharmacology; D011863:Radioimmunoassay; D013373:Substance P / Q000032:analysis*
D010455:Peptides; D013373:Substance P; D002766:Cholecystokinin