1. Department of Pharmacology, Dartmouth Medical School, Hanover, NH 03755, U.S.A.
2. Dartmouth Medical School, Hanover, NH 03755, U.S.A.
3. Thayer School of Engineering, Hanover, NH 03755, U.S.A.
4. Department of Pathology, Dartmouth Medical School, Lebanon, NH 03756, U.S.A.
5. Neuroscience Center at Dartmouth, Lebanon, NH 03756, U.S.A.
6. Department of Anesthesiology, Dartmouth-Hitchcock Medical Center, Lebanon, NH 03756, U.S.A.