Characterisation using FLIPR of human vanilloid VR1 receptor pharmacology

A full pharmacological characterisation of the recently cloned human vanilloid VR1 receptor was undertaken. In whole-cell patch damp studies, capsaicin (10 muM) elicited a slowly activating/deactivating inward current in human embryonic kidney (HEK293) cells stably expressing human vanilloid VR1 receptor, which exhibited pronounced outward rectification (reversal potential -2.1 +/- 0.2 mV) and was abolished by capsazepine (10 muM). In FLIPR(TM)-based Ca2+ imaging studies the rank order of potency was resiniferatoxin > olvanil > capsaicin > anandamide, and all were full agonists. Isovelleral and scutigeral were inactive (1 nM-30 muM) The potencies of capsaicin, olvanil and resiniferatoxin, but not anandamide, were enhanced 2- to 7-fold at pH 6.4. Capsazepine, isovelleral and ruthenium red inhibited the capsaicin (100 nM)-induced Ca2+ response (pK(B) = 6.58 +/- 0.02, 5.33 +/- 0.03 and 7.64 +/- 0.03, respectively). In conclusion, the recombinant human vanilloid VR1 receptor stably expressed in HEK293 cells acted as a ligand-gated, Ca2+-permeable channel with similar agonist and antagonist pharmacology to rat vanilloid VR1 receptor, although there were some subtle differences. (C) 2001 Published by Elsevier Science B.V.