AbstractIn experiments on cats the heart rate response to occlusion of the visceral and carotid arteries has been investigated. Of 69 combined or separate occlusions of the coeliac and superior mesenteric arteries 6 produced a tachycardia, in 9 no change in heart rate occurred, in the rest a bradycardia occurred. Of 32 common carotid artery occlusions 2 produced a bradycardia, in 4 no change in heart rate was observed and in the rest a tachycardia was produced. The bradycardia during visceral artery occlusion is interpreted as a reflex elicited from the sinoaortic baroreceptors and caused by the rise in blood pressure. It is further observed that the pressure increments caused by visceral artery occlusion have a maximum at subnormal systemic pressures (between about 65 and 100 mm Hg). This is contrary to the blood pressure rise caused by carotid artery occlusion which as a rule is greater the greater the systemic pressure, in accordance with the threshold concept for the baroreceptors.Therefore, at low systemic pressures (below about 110 mm Hg) a higher response to combined occlusion of the coeliac and superior mesenteric arteries than to carotid artery occlusion is the rule, the opposite is the case at higher systemic pressures.