Altered expression of endogenous cannabinoid receptor 2 (CB2), histaminergic receptors, sigma receptors, adenosine receptors (A1A and A2A receptors), and enzymes (BACE1, caspase 3, aspartryl cathepsin, and TrkB/C), as well as abnormalities in dopamine and serotonin neurotransmission, have been noted in AD. Here, CASP3 is linked to Alzheimer disease.