Permeability and single-channel properties of mesenteric, basilar, and septal (coronary) artery smooth-muscle P2X receptors

P2X(1) receptors for ATP are expressed in vascular smooth muscle and are th ought to underlie the native artery smooth muscle rapidly desensitising alp ha,beta -methylene ATP (alpha,beta -meATP) sensitive P2X receptor phenotype . We have characterised the ionic permeability and single-channel conductan ce from rat mesenteric, basilar, and septal (coronary) arteries. The relati ve permeabilities (P-X/P-NA) to methylamine, dimethylamine, and Tris were e ssentially the same for all three arteries and give an estimate of the mini mum diameter of the ionic pore as 0.8 nm. The P2X receptor channels in arte ries had a high calcium permeability (PCa2+/P-Na similar to3.5). In outside -out patches, alpha,beta -meATP evoked transient currents with a single-cha nnel conductance of similar to 12 pS (in physiological solution with 2.5 mM Ca2+ and 1 mM Mg2+). The single-channel conductance was increased to simil ar to 17 pS with a 0.1 mM Ca2+- and nominally Mg2+-free physiological solut ion. These properties for artery P2X receptors are essentially the same as for recombinant P2X1 receptors and confirm that homomeric P2X(1) receptors underlie the native P2X receptor current phenotype in these arteries. Drug Dec Res. 52:164-169, 2001. (C) 2001 Wiley-Liss, Inc.