The effect of amiloride, Gd3+
, and Na+
-free extracellular solution on the proton-gated current in DRG neurons. A-C) The use of amiloride produced a concentration-dependent and reversible inhibition of the proton-gated peak current without significantly modifying the steady-state current. In this and following graphs the black traces represent the control and the drug effect, the gray trace is after washout. The dotted line shown in this and following current recordings indicates the zero current, and the gray bar the time of pH 6.1 + drug application. The graphs display the first 3 seconds after the 5-s pH 6.1 perfusion. D) The use of Gd3+ also produced a reversible inhibition of the proton-gated current. E) The use of a Na+-free extracellular solution significantly decreased the current (to 4% of control current) reversibly. F) The normalized current amplitude versus pH relationship shows a sigmoidal dependence on the pH with a pH50 of 6.12 ± 0.1. Currents were normalized as a function of the current obtained with pH 4.