Volatile anaesthetics inhibit a cyclic AMP‐dependent sodium‐potassium current in cultured sensory neurones of bullfrog

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Abstract
1 Cultured dorsal root ganglion cells of the bullfrog were voltage-clamped in the whole-cell configuration. 2 An adenosine 3′:5′-cyclic monophosphate (cyclic AMP)-dependent cationic inward rectifier (IH) was inhibited by bath application of enflurane (0.2-0.8 mm) and halothane (0.2-0.5 mm), which thereby induced an outward current at the resting potential, and a membrane hyperpolarization in undamped cells. 3 The main effect of enflurane (0.5 mm) was to displace the steady-state IH activation curve to a hyperpolarizing direction by about 10 mV, as well as to reduce the maximum H-conductance to about 20%. 4 Forskolin (1–10 μm), which enhances IH by producing a depolarizing shift in the IH activation curve and increasing the maximum H-conductance, recruited IH even when the current had already been eliminated by enflurane (1 mm).