Lack of algesic effect of substance P on paravascular pain receptors

Abstract

Substance P (synthetic or extracted from intestine or central nervous system) is devoid of an algesic effect on paravascular pain receptors. The algesic effect of a SP-containing acetone HCl-extract from spinal cord is explained by its high content of potassium ions. SP-containing preparations which include an ammonium sulphate precipitation in the extraction procedure are algesic due to content of this salt. SP-containing extract from intestine were found to be contaminated with a bradykinin-like peptide of high algesic potency. These findings are discussed with regard to the restricted value of earlier results about central actions of SP-containing tissue extracts and with regard to the role of SP as a possible neurotransmitter.