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Electrophysiological and mechanical effects of substance P and acetylcholine on rabbit aorta.

1988; Wiley; Volume: 398; Issue: 1 Linguagem: Inglês

10.1113/jphysiol.1988.sp017042

1469-7793

Jean‐Louis Bény, Pascale Claude Brunet,

Neurobiology and Insect Physiology Research

1. The mechanical and electrical properties of smooth muscle cells of the rabbit aorta were recorded simultaneously using respectively a force transducer and a 3 M‐KCl‐filled glass microelectrode. 2. Acetylcholine had two effects depending on concentration. At low concentration, it caused a persistent endothelium‐dependent relaxation and hyperpolarization. At higher concentrations the acetylcholine endothelium‐dependent relaxation summed with an endothelium‐independent contraction. 3. Substance P caused a transient endothelium‐dependent relaxation and hyperpolarization. 4. Acetylcholine and substance P depolarized and contracted de‐endothelialized smooth muscle. When the de‐endothelialized strip was pre‐contracted by noradrenaline, acetylcholine depolarized the muscle but substance P did not. 5. In a 'cascade' experiment, the perfusate from an upstream intact aorta passed over a downstream de‐endothelialized strip. Acetylcholine and substance P relaxed the downstream strip showing that they released an endothelial humoral factor which relaxes smooth muscle. 6. The results suggest a constant release of a factor from the endothelial cells which hyperpolarizes the smooth muscle cells in the media. Activation of acetylcholine and substance P receptors on the endothelium accelerates the release of this factor and causes vasodilatation.