INHIBITION OF RAT HEPATOCYTE K+ CONDUCTANCE BY SEROTONIN

As evident from conventional electrophysiology, serotonin leads to a rapid and fully reversible depolarization of the rat hepatocyte cell membrane. At 10 mu mol/l serotonin, the depolarization approached 7.3 +/- 0.6 mV. The depolarization was paralleled by an increase of input resistance (by 29 +/- 4%) and a decrease of the K+ selectivity of the cell membrane (by 40 +/- 9%), thus pointing to a decrease of K+ conductance of the cell membrane. Accordingly, in whole-cell patch-clamp experiments, serotonin similarly led to a decrease of the cell membrane conductance (2.0 +/- 0.2 to 0.87 +/- 0.2 pS/mu m(2)) as well as to a decrease of the reversal potential(-29.6 +/- 5.2 to -10.1 +/- 2.4 mV). Ba2+ (10 mmol/l) depolarized the cell membrane by 21 +/- 1mV and abolished the depolarizing effect of serotonin. In conclusion, serotonin depolarizes the hepatocyte cell membrane by inhibition of K+ channels.