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Selective activation of heterologously expressed G protein‐gated K + channels by M 2 muscarinic receptors in rat sympathetic neurones
Author(s) -
FernandezFernandez Jose M.,
Wanaverbecq Nicolas,
Halley Pam,
Caulfield Malcolm P.,
Brown David A.
Publication year - 1999
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.1469-7793.1999.631ab.x
Subject(s) - muscarinic acetylcholine receptor , pirenzepine , g protein coupled inwardly rectifying potassium channel , transfection , carbachol , chemistry , g protein , muscarinic acetylcholine receptor m2 , muscarinic acetylcholine receptor m3 , acetylcholine , receptor , muscarine , biophysics , patch clamp , muscarinic acetylcholine receptor m1 , microbiology and biotechnology , pertussis toxin , endocrinology , biology , biochemistry , gene
1 G protein‐regulated inward rectifier K + (GIRK) channels were over‐expressed in dissociated rat superior cervical sympathetic (SCG) neurones by co‐transfecting green fluorescent protein (GFP)‐, GIRK1‐ and GIRK2‐expressing plasmids using the biolistic technique. Membrane currents were subsequently recorded with whole‐cell patch electrodes. 2 Co‐transfected cells had larger Ba 2+ ‐sensitive inwardly rectifying currents and 13 mV more negative resting potentials (in 3 m m [K + ] o ) than non‐transfected cells, or cells transfected with GIRK1 or GIRK2 alone. 3 Carbachol (CCh, 1–30 μ m ) increased the inwardly rectifying current in 70% of GIRK1+ GIRK2‐transfected cells by 261 ± 53% ( n = 6 , CCh 30 μ m ) at −120 mV, but had no effect in non‐transfected cells or in cells transfected with GIRK1 or GIRK2 alone. Pertussis toxin prevented the effect of carbachol but had no effect on basal currents. 4 The effect of CCh was antagonized by 6 n m tripitramine but not by 100 n m pirenzepine, consistent with activation of endogenous M 2 muscarinic acetylcholine receptors. 5 In contrast, inhibition of the voltage‐activated Ca 2+ current by CCh was antagonized by 100 n m pirenzepine but not by 6 n m tripitramine, indicating that it was mediated by M 4 muscarinic acetylcholine receptors. 6 We conclude that endogenous M 2 and M 4 muscarinic receptors selectively couple to GIRK currents and Ca 2+ currents respectively, with negligible cross‐talk.