[Structural changes in the vascular wall in vasoconstrictor and vasodilator exposures]

Noradrenaline vasoconstriction of the tail artery decreased external, internal diameters and the cross-section area of all the elements of the blood vessel wall. Papaverine vasorelaxation of the same artery increased the diameters but reduced the endothelium and adventitia areas. The data obtained suggest a close relation between the blood vessel tonus and the morphology of all the elements of the vessel wall.