ACETYLCHOLINE INDUCES CONTRACTION IN VERTEBRAL ARTERIES FROM TREATED HYPERTENSIVE PATIENTS

Endothelium-dependent vasodilatation to acetylcholine is abnormal in a nimal models of hypertension. This abnormality reflects a change in th e balance of relaxing and contracting factors produced in the vascular wall. In human cerebral arteries, endothelin has been implicated in t he abnormal vasoconstrictor response following subarachnoid hemorrhage . This study tests the hypothesis that cerebral arteriolar dilatation to acetylcholine is reduced in clinical hypertension due to an overpro duction of endothelin. Our results show that at high concentrations of muscarinic agonist (0.3-3 mu M), human vertebral arteries from hypert ensive patients contract whereas those from normotensive patients rema in maximally dilated. We conclude that the normal dilator response to acetylcholine is abrogated in vertebral arteries from treated hyperten sive patients but endothelin-1 does not contribute to the abnormal res ponsiveness.