Fig. 7
Adiponectin increases membrane excitability in TG neurons. A-D Representative traces (left) and bar chart (right) showing the effect of 100 nM adiponectin on Nav currents (INa, n = 8 cells, A), high-voltage activated (HVA) Ca2+ currents (n = 9 cells, B), sustained delayed-rectifier K+ currents (IDR, n = 12 cells, C), and transient outward A-type K+ currents (IA, n = 12 cells, D). TG neurons were held at -90 mV, and INa was stimulated with a series of depolarizing pulses ranging between -80 and + 80 mV. HVA Ca2+ currents were elicited from the holding potential of -60 mV with depolarizing pulses ranging between -80 and + 40 mV. To obtain the current–voltage relationship of IA and IDR, neurons were held at -80 mV and stimulated with step depolarizing pulses ranging from -70 tp + 70 mV in 10-mV increments. *p < 0.05 (vs. control), one-way ANOVA. E–F Representative traces (E) and bar chart (F) showing that adiponectin at 100 nM markedly increased the rate of action potential (AP) firing (n = 15 cells). Insets depicted at top represent the protocols of current injection. **p < 0.01 (vs. control), paired t test. G Effect of 100 nM adiponectin on the resting membrane potential of AP firing (n = 15 cells). H Bar chart showing that pretreatment of neurons with CK-4945 (10 μM, n = 9 cells), LY333531 (200 nM, n = 11 cells) or PKCβ2-IP (10 μM, n = 11 cells) abrogated the adiponectin-induced increase in the rate of AP firing. **p < 0.01, ***p < 0.001 (vs. control), paired t test. I Representative traces (left) and bar chart (right) revealing that pretreatment with TTA-P2 (3 μM) prevented the 100 nM adiponectin-induced increase in the rate of AP firing (n = 9 cells). J Protein abundance of Cav3.2 in NC-siRNA- or Cav3.2-siRNA-treated groups. Representative blots of at least 3 independent experiments are shown. **p < 0.05 (vs. NC-siRNA), unpaired t test. K Bar chart showing that treatment with Cav3.2-siRNA (n = 12 cells), but not NC-siRNA (n = 10 cells), prevented the 100 nM adiponectin-induced increase in the rate of AP firing. *p < 0.05 (vs. control + NC-siRNA), unpaired t test