Serotonin inhibits voltage-gated sodium current by cyclic adenosine monophosphate-dependent mechanism in bullfrog taste receptor cells

Abstract

We have investigated the effect of 5-hydroxytryptamine (serotonin) (5-HT) on the membrane properties of bullfrog taste receptor cells (TRCs) using patch-clamp technique. External application of 5-HT reversibly suppressed the voltage gated Na1 current (INa) in about half of the TRCs sampled. The magnitude of suppression of peak INa was dependent on the holding potential of the cell. Forskolin and cyclic adenosine monophosphate (cAMP) mimicked the suppressive effect of 5-HT on INa, but an internal protein kinase A-inhibitor potentiated INa. These results suggest that 5-HT suppresses INa of bullfrog TRCs via protein kinase A-dependent phosphorylation, resulting in suppression of the excitability of bullfrog TRCs. q 2000 Elsevier Science Ireland Ltd. All rights reserved.