Figure 3.

Efficacy of Cyt on α3 AChRs expressed by permanently transfected HEK cells is determined by whether the AChR contains a β2 or β4 subunit. Representative currents are shown for permanently transfected cell lines that express α3β2, α3β2α5, α3β4, and α3β4α5 AChRs. For each cell, a pair of currents are superimposed that reflect current activated by a near saturating (300 μM) concentration of ACh and a maximally effective concentration (300 μM) of Cyt. Clearly, the efficacy of Cyt relative to ACh in the cell lines that express the β2 subunit is far lower (5% or less) than that found for the cell lines that express the β4 subunit (∼80% or more).