BACE1 and Alzheimer disease: While Zuchner reported that selective stimulation of M1 muscarininc acetylcholine receptors (mAChRs) increased BACE1 protein expression, with the activation of M2 mAChRs having opposing effects on the level of BACE1 protein [209], Caccamo and colleagues reported an impressive and almost complete inhibition of BACE1 protein expression following treatment of the 3xTg-AD model with a selective M1 muscarinic agonist [210].