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Calcium permeability and block at homomeric and heteromeric P2X 2 and P2X 3 receptors, and P2X receptors in rat nodose neurones
Author(s) -
Virginio Caterina,
North R. A.,
Surprenant Annmarie
Publication year - 1998
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1111/j.1469-7793.1998.027bz.x
Subject(s) - homomeric , receptor , chemistry , nodose ganglion , ion channel , agonist , biophysics , extracellular , endocrinology , biochemistry , protein subunit , biology , vagus nerve , stimulation , gene
1 Whole‐cell recordings were made from HEK 293 (human embryonic kidney) cells stably transfected with cDNAs encoding P2X 2 , P2X 3 or both receptors (P2X 2/3 ) and from cultured rat nodose neurones. Nodose neurones all showed immunoreactivity for both P2X 2 and P2X 3 , but not P2X 1 , receptors. 2 Reversal potentials were measured in extracellular sodium, N‐ methyl‐D‐glucamine (NMDG) and NMDG containing 5 mM Ca 2+ ; the values were used to compute relative permeabilities ( P NMDG / P Na and P Ca / P Na ). P NMDG / P Na was not different for P2X 2 , P2X 2/3 and nodose neurones (0.03) but was significantly higher (0.07) for P2X 3 receptors. P Ca / P Na was not different among P2X 3 , P2X 2/3 and nodose neurones (1.2‐1.5) but was significantly higher (2.5) for P2X 2 receptors. 3 External Ca 2+ inhibited purinoceptor currents with half‐maximal concentrations of 5 mM at the P2X 2 receptor, 89 mM at the P2X 3 receptor and 15 mM at both the P2X 2/3 heteromeric receptor and nodose neurones. In each case, the inhibition was voltage independent and was overcome by increasing concentrations of agonist. 4 These results may indicate that Ca 2+ permeability of the heteromeric (P2X 2/3 ) channel is dominated by that of the P2X 3 subunit, while Ca 2+ block of the receptor involves both P2X 2 and P2X 3 subunits. The correspondence in properties between P2X 2/3 receptors and nodose ganglion neurones further supports the conclusion that the native α,β‐methylene ATP‐sensitive receptor is a P2X 2/3 heteromultimer.