Effects of substance P-(1-9) nonapeptide amide on inactivation of substance P in vitro.

The effects of substance P nonapeptide amide on inactivation of substance P by the guinea-pig ileum and urinary bladder preparations and of substance P hexapeptide amide, bradykinin and acetylcholine by the guinea-pig urinary bladder, have been investigated. Significant inhibition of inactivation of Substance P was found only in the urinary bladder. None of the other agents were significantly affected. These results suggest that the previously reported agonist effects of substance P nonapeptide may be due to inhibition of inactivation of SP in vivo and this effect is possibly specific.