Elevation of Substance P‐like Immunoreactivity in Rat Central Nervous System by Protease Inhibitors

Several substance P-rich areas in rat CNS had increased levels of substance P-like immunoreactivity following the intraventricular injection of the protease inhibitors SQ 20881, SQ 14225, and leupeptin. There were significant differences in response patterns from region to region, possibly on account of an interaction of anatomical, biochemical, or physiological variables. Although the compound SQ 14225 appeared to be the most potent of the inhibitors examined, it had no apparent effect on CNS substance P-like immunoreactivity when administered peripherally.