Referenced in: none

Automatically associated channels: Kv4.1 , Slo1

Title: Kinetics of P2X7 receptor-operated single channels currents.

Authors: T Riedel, I Lozinsky, G Schmalzing, F Markwardt

Journal, date & volume: Biophys. J., 2007 Apr 1 , 92, 2377-91

PubMed link: http://www.ncbi.nlm.nih.gov/pubmed/17189308

Abstract
Human P2X7 receptors were expressed in Xenopus laevis oocytes and single channels were recorded using the patch-clamp technique in the outside-out configuration. ATP4- evoked two types of P2X7 receptor-mediated single channel currents characterized by short-lived and long-lived openings. The short- and long-lasting open states had mean open times of approximately 5 and approximately 20 ms and slope conductances near -60 mV of 9 and 13 pS, respectively. The open probabilities of the short and long openings were strongly [ATP4-]-dependent with EC50 values of approximately 0.3 mM and approximately 0.1 mM ATP4-, respectively. The channel kinetics did not change significantly during sustained P2X7 receptor activation for several minutes, as was also observed in recordings in the cell-attached patch-clamp configuration. Activation and deactivation of the short openings followed exponential time courses with time constants in the range of 20 ms, and displayed a shallow [ATP4-] dependence of the activation process. The kinetics of the short channel openings at negative membrane potentials fitted well to a linear C-C-C-O model with two ATP4- binding steps at equal binding sites with a dissociation constant Kd of 139 microM.