This study was designed to determine the effects of glucagon-like peptides (GLP) on arterial blood pressure and heart rate. Although glucagon caused a minimal effect and GLP-1-(1-37) produced a moderate increase of both systolic and diastolic blood pressure, GLP-1-(7-36) amide induced the greatest increases in both parameters. Systolic and diastolic blood pressure and heart rate values increased when doses of the peptides were increased. By contrast, GLP-2 did not modify either arterial blood pressure or heart rate values. To determine whether the effects of GLP-1-(7-36) amide were mediated through catecholamines, the rats were pretreated with reserpine, propranolol, or phentolamine before administration of the peptide. In these three experimental groups, GLP-1-(7-36) amide increases mean arterial blood pressure and heart rate to the same level or even greater than that observed in nonpretreated rats. These findings indicate that GLP-1-(7-36) amide significantly increases arterial blood pressure and heart rate and that these effects are not mediated through catecholamines.