Drugs and reagents
All salts for Krebs solutions were of AnalaR grade or higher and obtained from BDH, Poole or Fisons, Loughborough. Chloroquine diphosphate, (±) adrenaline HCl, ethyl carbamate (urethane), Tween 80, N,N-dimethylacetamide and propylene glycol were obtained from Sigma, Poole. Heparin sodium (Multiparin 5000 IU ml-1) injection was obtained from CP Pharmaceuticals, Wrexham. MTBE was purchased from Fisons, Loughborough; Ro5-4864 was purchased from Fluka Chemika, Gillingham, Dorset; Hypnorm (fentanyl / fluanisone) was from Janssen Animal Health, Petteridge, Kent; Amprol Plus (Amprolium HCl / ethopabate) was from Merk Sharp & Dohme, Hertfordshire; sodium pentobarbitone from RMB Animal Health Ltd, Dagenham. 7-chloro-4-(5-diethylamino-1-methylpentyl-amino)-quinoline diphosphate was a gift from the Walter Reed Army Institute of Research, Washington D.C.; and clonazepam and diazepam were gifts from Hoffman-La Roche, Basel.