In Alzheimer’s disease brains there is a decline in the densities and/or function of, e.g., α2-adrenoceptor (Meana et al., 1992), acetylcholine (Tayebati et al., 2002, 2004), 5-HT1A serotonin (Mizukami et al., 2011; Butzlaff and Ponimaskin, 2016; Verdurand and Zimmer, 2017), and somatostatin receptors (Kumar, 2005; Gahete et al., 2010), but an increase in adenosine A1 receptors (Albasanz et al., 2008). The gene discussed is HTR1A; the disease is Alzheimer disease.