1. Vascular Physiology Research Group, Department of Biomedical Sciences, Colorado State University, Fort Collins, CO 80523, USA.
2. Department of Pharmacology, University of Vermont School of Medicine, Burlington, VT 05405, USA.
3. Department of Pharmacology, University of Nevada School of Medicine, Reno, NV 89557–0318, USA.
4. Department of Physiology, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
5. Department of Neurosurgery, University of Tennessee Health Science Center, Memphis, TN 38163, USA.
6. Department of Physiology and Pharmacology, University of Calgary, Calgary, Alberta T2N 4N1, Canada.