Cloned human and murine serotonin(3A) receptors expressed in human embryonic kidney 293 cells display different single- channel kinetics

In the present study, well-resolved single-channel events of cloned human and murine homomeric 5-hydroxytryptamine type 3 (h5-HT3A and m5-HT3A) receptors, expressed in human embryonic kidney 293 cells, are reported for the first time. 5-HT (1 muM) applied in Ca2+- and Mg2+-free external solution to excised outside-out membrane patches induced non-rectifying single- channel inward currents. These currents were not observed in untransfected cells or in the presence of the antagonist ondansetron (1 muM). The mean single-channel conductance of the h5-HT3A and m5-HT3A receptors was 48 +/- 8 pS and 46 +/- 7 pS, the mean reversal potential was 10.3 +/- 1.8 mV and 4.7 +/- 5.3 mV, respectively. The analysis of single-channel open-times revealed for both h5-HT3A and m5-HT3A receptors only one type of open state, but different mean open-times (7.1 +/- 2.9 ms vs. 4.1 +/- 0.8 ms) indicating species-dependent gating mechanisms of 5-HT3 receptors. (C) 2002 Elsevier Science Ireland Ltd. All rights reserv