Figure 4. Ca²⁺ permeability of human, mouse and chimeric ɛ-AChRs.

A, simultaneous recordings of whole-cell current (top) and Ca²⁺ transient (bottom) induced by nicotine (100 μm, horizontal thin line) in GH4C1 cells transiently transfected with wild-type human αβɛδ (left), mouse αβɛδ (middle) and human αβδ plus mouse ɛ (right) AChR subunit cDNAs. Holding potential, −70 mV. Traces are aligned and share the same temporal scale. B, linear relationships between ΔF/F and Q obtained from the cells shown in A. For these examples, the P_f values, calculated by normalizing the slopes obtained in A (standard medium) with respect to the mean slope obtained from calibration experiments (8.0 ± 0.4 nC⁻¹, dashed line) are 7.5% for human αβɛδ (^), and 3.4% and 3.5% for mouse αβɛδ (▵) and for human αβδ-mouse ɛ (□), respectively.