ABSTRACT
AIMTo investigate the role of serine/threonine protein phosphatases in regulation of cell signal transduction on voltage-dependent sodium channels in rat trigeminal ganglion (TRG) neurons. METHODSWhole-cell patch clamp techniques were used to record the total sodium current (INa-T) and the tetrodotoxin-resistant sodium current (INa-TTX-R) before and after okadaic acid, a potent inhibitor of the serine/threonine protein phosphatases 1 and 2A, perfusion on adult rat TRG neurons. RESULTS1μmol*L-1 okadaic acid inhibited INa-T by (20±13)% (n=9, P<0.05) and INa-TTX-R by (4±3)% (n=6, P<0.05), respectively. The inhibition on INa-T was significantly greater than that on INa-TTX-R (P<0.05). Furthermore, 1μmol*L-1 okadaic acid produced significant 3-4 mV hyperpolarizing shifts in the conductance-voltage curves of INa-T, while it had no effect on that of INa-TTX-R. CONCLUSIONThe serine/threonine protein phosphatases take part in the regulation of total and TTX-R sodium channels on rat TRG neurons. In addition, small-diameter TRG neurons express various voltage-gated sodium channel with different sensitivity to okadaic acid.