FIGURE 1.

NMU selectively increased I_A in small DRG neurons. A, isolation of I_A. Na⁺ currents, Ca²⁺ currents, and Ca²⁺-activated K⁺ currents have been eliminated (see “Experimental Procedures”). Left, the membrane voltage was held at −80 mV and I_A was isolated by a two-step voltage protocol. Right, the remaining current after off-line subtraction of the noninactivating portion of current remaining after the prepulse to −10 mV. This protocol is used for isolation of I_A in all figures. B and C, representative current traces and the time course showed that I_A (n = 7, B), but not sustained delayed rectifier K⁺ current (I_DR) (n = 9, C), was significantly increased during exposure to 1 μm NMU. D, summary data of current density showed that 1 μm NMU selectively increased I_A. E, dose-response curve for the stimulatory effects of NMU on I_A. The line represents the best fit of the data points to the sigmoidal Hill equation. Number of cells tested at each concentration of NMU is indicated in parentheses. F, time course and exemplary traces showed no effect of 1 μm NMU on I_A in the presence of 4-AP (n = 5). ***, p < 0.001 versus control.