Fig. 1.

5-HT induces a slow depolarization in AH/type 2 cells during which membrane conductance decreases and the AH is inhibited. A, In the presence of the 5-HT_1Aantagonist NAN-190 and the 5-HT_3/4 antagonist tropisetron, the response to 5-HT is a uniphasic depolarization associated with an increase in input resistance. The top trace depicts the membrane potential, and the bottom trace indicates current injected through the recording pipette. The downward deflections in the top trace represent the electrotonic responses to the injections of hyperpolarizing current pulses.B, At a faster sweep speed, the pronounced AH (top trace) can be seen after the action potential in the control record. The addition of 5-HT (1.0 μm) to the superfusing medium blocks the AH. The bottom tracedepicts depolarizing current injected through the recording pipette to evoke action potentials.