1. From the Departments of Pharmacology,2Physiology & Biophysics, and
2. School of Biomolecular and Biomedical Sciences, Conway Institute, University College Dublin, Dublin, Ireland.
3. Physiology & Biophysics, and4Ophthalmology, Dalhousie University, Halifax, Nova Scotia, Canada; and the
4. From the Departments of Pharmacology,4Ophthalmology, Dalhousie University, Halifax, Nova Scotia, Canada; and the