Effects of phorbol-12,13-dibuterate on sodium currents and potassium currents in rat trigeminal ganglion neurons

Abstract

The effects of phorbol-12,13-dibuterate (PDBu) on total sodium current (I_Na-total), tetrodotoxin-resistant sodium current (I_Na-TTXr), 4-AP-sensitive potassium current (I_A) and TEA-sensitive potassium current (I_K) in trigeminal ganglion (TG) neurons were investigated. Whole-cell patch clamp techniques were used to record ion currents in cultured TG neurons of rats. Results revealed that 0.5 μmol/L PDBu reduced the amplitude of I_Na-total by (38.3±4.5)% (n=6, P<0.05), but neither the G-V curve (control: V_0.5=−17.1±4.3 mV, k=7.4±1.3; PDBu: V_0.5=−15.9±5.9 mV, k=5.9±1.4; n=6, P>0.05) nor the inactivation rate constant (control: 3.6±0.9 ms; PDBu: 3.6±0.8 ms; n=6, P>0.05) was altered. 0.5 μmol/L PDBu could significantly increase the amplitude of I_Na-TTXr by (37.2±3.2)% (n=9, P<0.05) without affecting the G-V curve (control: V_0.5=−14.7±6.0 mV, k=6.9± 1.4; PDBu: V_0.5=−11.1±5.3 mV, k=8.1±1.5; n=5, P>0.05) or the inactivation rate constant (control: 4.6±0.6 ms; PDBu: 4.2±0.5 ms; n=5, P>0.05). 0.5 μmol/L PDBu inhibited I_K by (15.6±5.0) % (n=16, P<0.05), and V_0.5 was significantly altered from − 4.7±1.4 mV to −7.9 ±1.8 mV (n=16, P<0.05). I_A was not significantly affected by PDBu, 0.5 μmol/L PDBu decreased I_A by only (0.3±3.2)% (n=5, P>0.05). It was concluded that PDBu inhibited I_Na-total but enhanced I_Na-TTXr, and inhibited I_K without affecting I_A. These data suggested that the activation of PKC pathway could exert the actions.

Keywords

Phorbol-12,13-dibuterate / trigeminal ganglion neurons / sodium channel / potassium channel

References

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