B-973, a novel piperazine positive allosteric modulator of the α7 nicotinic acetylcholine receptor

The alpha7 (alpha 7) nicotinic acetylcholine receptor is a therapeutic target for cognitive disorders. Here we describe 3-(3,4-difluoropheny1)-N-(1-(6-(4-(pyriclin-2-y1)piperazin-1-y1)pyrazin-2-371)ethyl)propanamide (B-973), a novel piperazine-containing molecule that acts as a positive allosteric modulator of the a7 receptor. We characterize the action of B-973 on the a7 receptor using electrophysiology and radioligand binding. At 0.1 mM acetylcholine, 1 mu M B-973 potentiated peak acetylcholine-induced currents 6 -fold relative to maximal acetylcholine (3 mM) and slowed channel desensitization, resulting in a 6900 -fold increase in charge transfer. The EC50 of B-973 was approximately 0.3 mu M at acetylcholine concentrations ranging from 0.03 to 3 mM. At a concentration of 1 mu M, B-973 shifted the acetylcholine BC50 of peak currents from 0.30 mM in control to 0.007 mM. B-973 slowed channel deactivation upon acetylcholine removal (tau=50 s) and increased the affinity of the alpha 7 agonist [H-3]A-585539. In the absence of exogenously added acetylcholine, application of B-973 at concentrations > 1 1 mu M induced large methyllycaconitine-sensitive currents, suggesting B-973 can function as an Ago-PAM at high concentrations. B-973 will be a useful probe for investigating the biological consequences of increasing alpha 7 receptor activity through allosteric modulation.