Regeneration of the rat carotid artery after clipping injury. Part II. A pharmacological study.

This study investigated the natural course of functional recovery of the vascular endothelium and smooth muscle after clipping injury of the rat carotid artery. Vascular injury was induced by clipping the right carotid arteries of Wistar rats. The contractile response to KCl, serotonin (5-hydroxytryptamine), and norepinephrine was decreased immediately after arterial injury. The response to KCl and serotonin recovered within 8 weeks, whereas the response to norepinephrine recovered after 12 weeks. Endothelium-dependent relaxation also disappeared immediately after clipping injury, but the recovery of relaxation in response to acetylcholine and adenosine triphosphate was observed within 1 week. Four weeks after clipping injury, higher doses of acetylcholine induced slight arterial contraction. These findings suggest that the recovery of smooth muscle contractility was slower than the process of endothelial regeneration in the rat carotid artery after clipping injury. Endothelium-dependent relaxation recovered within only a week, although the characteristics of the arterial cholinergic receptors may have changed in the chronic recovery stage.