Regional histaminergic potencies in rabbit systemic circulation.

1. Regional activity of histamine was studied in various rabbit arteries, including segments of the aorta, aortic branches, branchout regions and arteries to fore and hind limbs by dose-response experiments. 2. Local histaminergic potencies were found to be heterogenceous. Circular and longitudinal smooth muscle responsivity in the aorta increased in the distal direction; aortic branches have their own histaminergic response characteristics beginning from their branchouts. Paired arteries (right and left subclavia, renal and iliac) possess matching histaminergic activities. 3. The observed characteristics of the responses suggest predetermined distribution of histaminergic activities along systemic circulation which may be regulatory in the distribution of blood.