[1] Univ Liverpool, Dept Pharmacol & Therapeut, Liverpool L69 3GE, Merseyside, England
[2] Univ W Indies, Fac Med Sci, Pharmacol Unit, St Augustine, Trinidad Tobago
[3] Univ Dundee, Biomed Res Ctr, Dundee, Scotland
[4] Univ Tsukuba, Ctr Tsukuba Adv Res Alliance, Tsukuba, Ibaraki 305, Japan