Rivera-Acevedo, Ricardo E2; Pless, Stephan Alexander5; Schwarz, Stephan K W4; Ahern, Christopher A4
1 ILF-Secretariat, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, Københavns Universitet2 Department of Anesthesiology, Pharmacology & Therapeutics, The University of British Columbia, Vancouver, BC, Canada.3 Medicinal Chemistry Research, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, Københavns Universitet4 unknown5 Medicinal Chemistry Research, Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, Københavns Universitet
Transient receptor potential vanilloid subfamily member 1 channels are polymodal sensors of noxious stimuli and integral players in thermosensation, inflammation and pain signaling. It has been shown previously that under prolonged stimulation, these channels show dynamic pore dilation, providing a pathway for large and otherwise relatively impermeant molecules. Further, we have shown recently that these nonselective cation channels, when activated by capsaicin, are potently and reversibly blocked by external application of quaternary ammonium compounds and local anesthetics. Here we describe a novel phenomenon in transient receptor potential channel pharmacology whereby their expression levels in Xenopus laevis oocytes, as assessed by the magnitude of macroscopic currents, are negatively correlated with extracellular blocker affinity: small current densities give rise to nanomolar blockade by quaternary ammoniums and this affinity decreases linearly as current density increases. Possible mechanisms to explain these data are discussed in light of similar observations in other channels and receptors.