Hyposmotic membrane stretch potentiated muscarinic receptor agonist-induced depolarization of membrane potential in guinea-pig gastric myocytes

Abstract

Aim: To investigate the relationship between hyposmotic membrane stretch and muscarinic receptor agonist-induced depolarization of membrane potential in antral gastric circular myocytes of guinea-pig. Methods: Using whole cell patch-clamp technique recorded membrane potential and current in single gastric myocytes isolated by collagenase. Results: Hyposmotic membrane stretch hyperpolarized membrane potential from -60.0mV±1.0mV to -67.9mV±1.0mV. TEA (10mmol/L), a nonselective potassium channel blocker significantly inhibited hyposmotic membrane stretch-induced hyperpolarization. After KCl in the pipette and NaCl in the external solution were replaced by CsCl to block the potassium current, hyposmotic membrane stretch depolarized the membrane potential from -60.0 mV±1.0mV to -44.8 mV±2.3mV (P<0.05), and atropine (1 μmol/L) inhibited the depolarization of the membrane potential. Muscarinic receptor agonist Carbachol depolarized membrane potential from -60.0mV±1.0mV to -50.3 mV±0.3mV (P<0.05) and hyposmotic membrane stretch potentiated the depolarization. Carbachol induced muscarinic current (Icch) was greatly increased by hyposmotic membrane stretch. Conclusion: Hyposmotic membrane stretch potentiated muscarinic receptor agonist-induced depolarization of membrane potential, which is related to hyposmotic membrane stretch-induced increase of muscarinic current.