Department of Pharmacy and Pharmacology, University of Bath, Bath, , UK1
Pharmaceutical Sciences Research Institute, Aston University, Birmingham, , UK2
Department of Clinical Veterinary Science, University of Bristol, Langford, , UK3
130 Cornwall Road, Ruislip Manor, Middlesex, , UK4
Author for correspondence: Michael Brown. Tel: +44 1225 323340. Fax: +44 1225 826114. e-mail: prsmrb{at}bath.ac.uk