Figure 6. Heteromeric 5-HT₃A(C312A)/5-HT_3B receptors exhibit weak function.

A, 5-HT (100 μm) activated large whole-cell currents mediated by heteromeric 5-HT₃AB receptors. Representative currents recorded from a cell transiently transfected with cDNAs encoding WT 5-HT₃A and WT 5-HT₃B subunits. Note that the current desensitized rapidly, a hallmark of heteromeric receptor function. B, a representative 5-HT-evoked current recorded from a cell expressing homomeric 5-HT₃A receptors. The current decayed slowly. C, a representative 5-HT-evoked current recorded from a cell transfected with cDNAs encoding 5-HT₃A(C312A) and 5-HT₃B subunits desensitized rapidly. D, bar graph depicting the maximal 5-HT-activated current densities expressed as current amplitude (pA) normalized to cell membrane capacitance (pF), recorded from cells expressing WT 5-HT₃AB receptors (n= 8), 5-HT₃B subunits (n= 3), 5-HT₃A(C312A) receptors (n= 5) and 5-HT₃A(C312A)/5-HT₃B receptors (n= 4). Error bars represent ±s.e.m. Statistical analysis (ANOVA, post hoc Bonferroni's test) reveals that the 5-HT-evoked current density recorded from cells expressing 5-HT₃A(C312A) and 5-HT₃B subunits together was greater than current densities recorded from cells expressing either subunit alone (*P < 0.05).