[1] ROYAL COLL SURG ENGLAND,INST BASIC MED SCI,DEPT PHARMACOL,LONDON WC2A 3PN,ENGLAND
[2] LONDON HOSP,COLL MED,DEPT MORBID ANAT,LONDON E1 1BB,ENGLAND
[3] ROYAL MELBOURNE INST TECHNOL,DEPT APPL PHYS,MELBOURNE,VIC 3001,AUSTRALIA
[4] MERCK FROSST LABS,DEPT PHARMACOL,POINTE CLAIRE DO H9R 4P8,QUEBEC,CANADA