Responses of vessel walls to chronically applied electrical stimuli

8 mm long sections of common carotid arteries of conscious, freely moving rabbits were electrically stimulated with DC-impulses by chronically implanted gold-electrodes daily for 1/2 h or two times 1/2 h per day for 4--6 weeks. The electrodes were arranged in such a way that the wall was stimulated transmurally, In the initial phase the tension of the vessel wall increased. After 1/2 h of stimulation the artery wall relaxed at the stimulated section. Repetition of stimuli led to smooth muscle cell proliferation within the stimulated region. The smooth muscle cells formed a cushion protruding into the lumen of the artery mainly at the anodic site of the stimulation-arrangement. The proliferating cells were smaller than those of the underlying tunica media. They were identified as smooth muscle cells by electron-microscopy, contained relatively more lysosomes and endoplasmic reticulum than the original media-cells and produced collagen-fibrils and elastic fibrils as an extracellular matrix material. Below very thick cushions of smooth muscle cells necrosis developed. Animals which were additionally fed with 2% cholesterol in normal food developed typical atheromatous plaques at the site of the anodic stimuli.