ADORA2A and Alzheimer disease: NA and AD seem to perform the primary function of platelet aggregation, potentiation of stimulus induced aggregation and secretion along with the inhibition of adenylate cyclase by activation of the α2-ARs.17 Hence, it seems that the aggregatory response of platelets to AD is induced by selective α2-AR agonists (e.g. clonidine or lofexidine),18,19 whereas it can be inhibited by using α2-AR antagonists.