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. 2015 Apr 10;172(12):3126–3140. doi: 10.1111/bph.13113

Figure 4.

Figure 4

Characterization of IM in TC neurons of the VB. (A) Representative current traces evoked by a depolarizing voltage step from −65 to −45 mV (duration 4 s) recorded under control conditions and in the presence of Ret. Each test pulse was preceded by a short depolarization (pre-pulse; −45 mV, 80 ms) in order to inactivate fast-transient Ca2+ currents which were not affected by Ret application (see magnification of the pre-pulse). (B, C) Currents activated by Ret (B) or inhibited by XE991 (C) were isolated by graphical subtraction (Ret − control; control − XE991). Subtracted currents showed a slow activation and deactivation, typical for IM. (D, E) The Ret-activated current blocked by oxo-M and the diclofenac-sensitive current revealed typical IM kinetics. (F, H) Current–voltage relationship of the Ret-sensitive current. A fast hyperpolarizing ramp, affecting only constitutively open channels, was applied under control conditions in the presence of Ret and Ret + XE991. The Ret-sensitive current was obtained by subtracting control currents from the current activated by Ret and reversed at −94.04 ± 2.8 mV (n = 9), close to the calculated EK of −103 mV. (G) Bar graph showing the changes in current amplitude (voltage steps from a holding potential of −65 to −45 mV were analysed). Ret application significantly increased the current amplitude compared with control conditions. Adding Kv7 channel blockers [XE991 or linopirdine (lino)] reversed this effect. XE991 alone (i.e. without Ret) induced a pronounced current reduction; however, this was not significant. Wash-in of XE991 before Ret application prevented current activation by Ret. The presence of the muscarinic agonist oxo-M decreased the Ret-evoked current. Diclofenac (diclo) significantly increased the current amplitude, which was abolished by adding XE991 before or after drug application. Data are presented as mean ± SEM. For Ret: repeated-measures anova: F = 4.57; P = 0.005; for oxo-M: repeated-measures anova: F = 12.29; P < 0.0001; for diclo: repeated-measures anova: F = 14.85; P = 0.0002; Newman–Keuls post hoc test: *P < 0.05, **P < 0.01, ***P < 0.001 versus respective control as suggested by the horizontal bars.