Erythrina mulungu Alkaloids Are Potent Inhibitors of Neuronal Nicotinic Receptor Currents in Mammalian Cells
Figure 4
Concentration dependence of the blockade of nicotinic receptor-mediated currents by (+)-11α-hydroxyerythravine.
A. Currents elicited by 2-s pulses of acetylcholine 50 µM (blue bars) in a HEK 293t cell expressing α4β2 receptors in the presence of increasing concentrations of (+)-11α-hydroxyerythravine (0.003 to 1 µM; red bars). B. Currents elicited by 0.5 s pulses of acetylcholine 300 µM (blue bars) in a hippocampal neuron expressing α7* receptors in the presence of increasing concentrations of (+)-11α-hydroxyerythravine (0.3 to 100 µM; red bars). The alkaloid was pre-applied on the bathing solution and was in equilibrium during the agonist pulse. C. Concentration-response curves showing the area under the current traces obtained as in A and B. Non-linear regression using the Hill equation yielded an IC50 of 12 nM and a Hill coefficient of –0.6 for α4β2 receptors (empty circles) and an IC50 of 5 µM and a Hill coefficient of –0.5 for native α7* receptors (filled triangles). Data are presented as means ± SEM (n = 3 cells).