Cardiovascular effects of synthetic substance P.

The cardiovascular action of substance P (SP) has been studied in anaesthetized dogs. An analeptic respiratory and hypotensive action has been noted. The chronology of both effects would suggest that SP could be rapidly metabolized. The action of SP on respiration and general metabolism could be attributed either to one of its metabolites or to a secondary effect. It has not yet been stated to which mechanism--enzymatic or hormonal--it might be due.