Screening of the <i>Erythrina</i> alkaloids.

<p>A. Hippocampal neurons constitutively expressing α7* nicotinic receptors. Currents elicited by 0.5-s pulses of acetylcholine 100 µM (blue bars) were partially and reversibly blocked by co-application with 100 µM of (+)-11α-hydroxyerysotrine, (+)-erythravine and (+)-11α-hydroxyerythravine (red bars). Membrane potentials were fixed at –67 mV. <b>B.</b> HEK 293 cells heterologously expressing α4β2 nicotinic receptors. Currents elicited by 2-s pulses of acetylcholine 50 µM (blue bars) were partially and reversibly blocked by co-application with 10 µM of (+)-11α-hydroxyerysotrine, (+)-erythravine and (+)-11α-hydroxyerythravine (red bars). Membrane potentials were fixed at –87 mV. <b>C.</b> PC12 cells constitutively expressing α3* nicotinic receptors. Currents elicited by 0.5 s pulses of acetylcholine 100 µM (blue bars) were partially and reversibly blocked by co-application with 50 µM of (+)-11α-hydroxyerysotrine, (+)-erythravine and (+)-11α-hydroxyerythravine (red bars). Membrane potentials were fixed at –87 mV. All experiments were performed in the presence of 0.15 µM of TTX (only in experiments with neurons) and 0.5 µM of atropine sulfate. Traces are representative of 3 to 5 independent cells and the mean responses are shown in the bar graphs to the right as the percentages of the current obtained from the first acetylcholine pulse, with error bars being the SEM. Black bars represent the current at peak and grey bars represent the area under the trace for a period of 1.5 s for α4β2 HEK 293 cells and PC12 cells and 1 s for hippocampal neurons, starting at the beginning of the agonist pulse. HEt, (+)-11α-hydroxyerysotrine; Ev, (+)-erythravine; HEv, (+)-11α-hydroxyerythravine.</p