1. Department of Medicine, McMaster University, Hamilton, Ontario, Canada L8N 3Z5
2. Department of Biology, McMaster University, Hamilton, Ontario, Canada L8S 4K1
3. Department of Pharmacology and Toxicology, University of Western Ontario, London, Ontario, Canada N6A 5C1
4. Department of Physiology, University of Western Ontario, London, Ontario, Canada N6A 5C1