Fig. 3
Current- and voltage-clamp recordings in LC-NE neurons. a Representative tracings of transmembrane voltage responses from hyperpolarizing to suprathreshold current injections revealed a significant delay in the action potential (AP) firing latency of LC-NE neurons in Ndn +m/−p mice. b The delay in the AP firing of LC-NE neurons in both WT and Ndn +m/−p mice can be eliminated using 4-aminopyridine (4-AP). The representative tracings were from the different neurons of a. c The delay in the AP firing latency from current injections was significantly increased in LC-NE neurons in Ndn +m/−p mice (n = 17 cells from 12 animals) than in those in WT mice (n = 16 cells from 13 animals). AP firing delay in both WT (n = 5 cells from 4 animals) and Ndn +m/−p mice (n = 5 cells from 3 animals) decreased after applying 5 μM of 4-aminoantipyrine (4-AP) in the bathing ACSF. Asterisks indicate a significant difference between WT and Ndn +m/−p. Statistical analyses were performed using Student’s t tests between WT and Ndn +m/−p mice. d AP numbers elicited by current injection were lower in Ndn +m/−p mice subjected to 80-pA and 100-pA current injection, and the difference was eliminated by 4-AP. Asterisks indicate a significant difference between WT and Ndn +m/−p. Statistical analyses were performed using ANOVA with LSD posthoc analysis. e Recording of IA in LC-NE neurons. Representative tracings illustrated the effects of voltage stepping from − 90 to 0 mV (gray line, IA + IDR) and from − 40 to 0 mV (black line, IDR). f Subtraction of the two currents yielded the fast activated and inactivated IA current; representative tracings of IA currents of LC-NE neurons in the Ndn +m/−p (red line) and WT (black line) mice. The IA currents of the Ndn +m/−p (orange line) and WT (blue line) mice can be suppressed by 4-AP. g–i The IA current (g), current density (h), and decay time constant (i) were increased in the LC-NE neurons in Ndn +m/−p (n = 15 cells from 10 animals) than in those in WT mice (n = 16 cells from 9 animals). Statistical analyses were performed using Student’s t test. Data are presented as mean ± SEM