Intracerebroventricular injections (140-4300 pmol) of a 60-residue polypeptide (now designated PEC-60) isolated from pig intestine produced a dose-dependent increase (peak action 21% +/- 2; ED50 value of 1.7 nmol for the peak effect) in mean arterial blood pressure (MAP) in the awake, unrestrained male rat. The heart rate (HR) was significantly reduced with the highest doses used (1400 and 4300 pmol). The pancreatic secretory trypsin inhibitor (PSTI), with a high degree of sequence similarity to PEC-60, did not significantly change MAP and HR (4300 pmol). These results may indicate a biological role for the putative PEC-60-like peptide demonstrated within central catecholamine cardiovascular neurons.