1. From Microvascular Research Laboratories, Bristol Heart Institute, Department of Physiology (A.V.B., O.A.S., S.J.H., D.O.B.) and Laboratories for Integrative Neuroscience and Endocrinology (C.P.G., J.B.U.), University of Bristol, and BHF Glasgow Cardiovascular Research Centre (W.H.M., A.H.B.), University of Glasgow, UK. Present address for A.V.B.: Division of Vascular Oncology and Metastasis A190, DKFZ, Im Neuenheimer Feld 581 (TP4), D-69120 Heidelberg, Germany.