1. Alan Edwards Centre for Research on Pain, McGill University, Montreal, QC, Canada
2. Department of Anesthesia, McGill University, Montreal, QC, Canada
3. Division of Experimental Medicine, McGill University, Montreal, Quebec, Canada
4. Department of Physiology, McGill University, Montreal, QC, Canada
5. Division of Pharmacology & Toxicology, School of Pharmacy, University of Texas at Austin, Austin, TX, USA