Fig. 3.
Serotonin depresses the evoked IPSC. Although the serotonin inward current is blocked by the 5-HT2 antagonist ritanserin, the depression of the IPSC by serotonin is blocked by the 5-HT1B antagonist pindolol. A, Serotonin (3 μm; filled bars) causes an inward current and also reversibly depresses the IPSC amplitude (transient outward currents evoked every 30 sec). In the presence of ritanserin (3 μm; open bar) serotonin still depresses the IPSC, but the inward current is blocked. Shown is a continuous record of membrane current, except for a 13 min break where indicated, from cell clamped at −50 mV. CNQX (10 μm) andd-AP5 (50 μm) are present throughout.B, Left, Plot of time course of experiment from another cell: serotonin (3 μm) reversibly depresses the evoked IPSC (ii) but was ineffective in the presence of pindolol (3 μm; iv).Right, Single records from this experiment, at times indicated on the plot, showing the IPSC preceded by current resulting from −5 mV test step. The cell was voltage-clamped at −50 mV in the continued presence of ritanserin (3 μm) as well as CNQX (10 μm) and d-AP5 (50 μm).