Figure 3. Properties of I_5-HT in the presence of ZD-7288.

A, chart records showing the response of an 8-day-old facial motoneurone voltage clamped at −68 mV in 12 mm K⁺ ACSF to bath application of 5-HT (10 μm, 60 s, horizontal bar) before (a), and during (b), superfusion with ZD-7288 (10 μm). Holding current was −304 pA in a and −276 pA in b. Vertical deflections are attenuated current responses to various voltage commands. Note that the 5-HT-evoked inward current observed prior to ZD-7288 application was replaced by an outward current in its presence. Ac, superimposed current responses (upper traces) evoked by a voltage command protocol (lower trace) before, and in the presence of, ZD-7288. Note the selective block of I_h over the currents evoked by the depolarizing component of the command voltage. Holding current was −26 pA before and −6 pA after addition of ZD-7288. B and C, current-voltage (I–V) relationships, generated using a voltage ramp protocol (see Methods), obtained before and during 5-HT application in the absence (Ba) and the presence (Ca) of ZD-7288 (3 μm). Subtracted I_5-HT in the absence and presence of ZD-7288 (3 μm) is shown in Bb and Cb, respectively. All records shown in B and C are taken from the same 7-day-old facial motoneurone voltage clamped at −68 mV in 12 mm K⁺ ACSF. Note that in the absence of ZD-7288, I_5-HT was inward over the voltage range tested while in its presence, I_5-HT was linear over the whole voltage range with a clear reversal potential at −58 mV.