1. Departments of Neurobiology and Anatomy (H.J.B.), Robert C. Byrd Health Sciences Center, Morgantown, West Virginia 26506-9128;
2. Departments of Physiology and Pharmacology (J.M.C., S.N.A., S.M.H., I.H., C.J.M.; C.CN., B.H.J., R.L.G.), Robert C. Byrd Health Sciences Center, Morgantown, West Virginia 26506-9128;
3. Department of Anatomy and Cell Biology (M.N.L.), Schulich School of Medicine and Dentistry, The University of Western Ontario, London, Ontario, Canada N6A 5C1