Figure 1.

Coexpression of 5-HT₃R and nAChR α4 subunits alters the kinetics of the 5-HT-induced ion current. (A) Ion currents evoked with 10 μM 5-HT at holding potentials of −60 mV and −20 mV (large and small responses, respectively) in oocytes expressing the 5-HT₃R subunit alone (Upper Left) or a combination of the 5-HT₃R subunit and the indicated nAChR subunit. (Inset) The current evoked at −20 mV in oocytes expressing 5-HT₃R and nAChR α4 subunits is biphasic, whereas the corresponding currents from all other subunit combinations are monophasic and indistinguishable. (B) Ion currents evoked with either 10 μM 5-HT or 1 mM ACh in the same oocyte injected with cDNAs encoding the subunits indicated. The lower right trace shows that the amount of α4 cDNA injected was sufficient to obtain a large ACh-evoked ion current through heteromeric nAChR. The holding potential was −60 mV in all oocytes.