Inhibition of prolyl oligopeptidase by KYP-2047 fails to increase the extracellular neurotensin and substance P levels in rat striatum

► We examined the effects of PREP inhibition on rat brain peptide levels. ► For the first time in PREP studies, peptides were measured in brain microdialysates. ► Brain PREP was inhibited with KYP-2047 (50 μmol/kg i.p.). ► No changes in extracellular neurotensin or substance P levels were detected. ► PREP does not regulate the extracellular levels of neurotensin or substance P.