INHIBITION OF RAT HEPATOCYTE K+ CONDUCTANCE BY SEROTONIN

As evident from conventional electrophysiology, serotonin leads to a r apid and fully reversible depolarization of the rat hepatocyte cell me mbrane. At 10 mu mol/l serotonin, the depolarization approached 7.3 +/ - 0.6 mV. The depolarization was paralleled by an increase of input re sistance (by 29 +/- 4%) and a decrease of the K+ selectivity of the ce ll membrane (by 40 +/- 9%), thus pointing to a decrease of K+ conducta nce of the cell membrane. Accordingly, in whole-cell patch-clamp exper iments, serotonin similarly led to a decrease of the cell membrane con ductance (2.0 +/- 0.2 to 0.87 +/- 0.2 pS/mu m(2)) as well as to a decr ease 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 abolishe d the depolarizing effect of serotonin. In conclusion, serotonin depol arizes the hepatocyte cell membrane by inhibition of K+ channels.