Abstract To determine whether the responses of resting membrane potential (RMP) and hyperpolarization-activated current ( I H) are altered by the application of ouabain, one of the Na +-K + pump inhibitors, in neonatal rat small-diameter (<30 μm) nodose ganglion (NG) neurons, we examined the effects of 1 μM ouabain on those responses using perforated patch-clamp techniques. In current-clamp mode, the RMP was 40.2 ± 1.6 mV ( n = 31). Twenty of 31 cells tested were depolarized by ouabain application, and these responses were associated with an increase in the cell input resistance. In the remaining 11 cells studied, 3 showed hyperpolarization in response to ouabain and 8 showed no effect on RMP. In voltage-clamp mode, 1 μM ouabain application enhanced the I H in all of 10 neurons examined. These results suggest that ouabain application at 1 μM is capable of setting both the RMP level and the neuronal excitability in small-diameter NG neurons.