Abstract
In freshly dispersed rat parotid acinar cells, 10 μM carbachol increased outward currents at 0 mV and also inward currents at −70 mV recorded with the whole-cell clamp method using patch pipettes containing 1 mM EGTA. When EGTA in the pipette was increased to 2.4 mM, carbachol increased only outward currents and a further increase of EGTA to 4 mM blocked the carbachol response. Effects of changes in external K+ and Cl− concentrations suggested that outward currents were carried by K+ and inward by Cl−. Effects of Ca2+ removal from the medium differed between experiments with 0 and 5 mM ATP in the patch pipettes. When pipettes contained no ATP, responses evoked by repeated applications of 10 μM carbachol (0.5–1 min) at 1.5–4 min intervals decreased only slowly after Ca2+ removal, outward currents being reduced to 90±6% and inward currents to 47±11% (n=6) in 10 min. On the other hand, when 5 mM ATP was included in the electrodes, Ca2+ removal abolished the carbachol responses in about 5 min (n=4). It was also found that tetraethylammonium (5 mM) strongly reduced both currents, by blocking muscarinic receptors, while Ba2+ (2.4 mM) inhibited only the outward K+ current.
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Shigetomi, T., Hayashi, T., Ueda, M. et al. Effects of Ca2+ removal and of tetraethylammonium on membrane currents induced by carbachol in isolated cells from the rat parotid gland. Pflügers Arch. 419, 332–337 (1991). https://doi.org/10.1007/BF00371115
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DOI: https://doi.org/10.1007/BF00371115