Dysfunction of the nicotinic receptors was described during normal aging [90] and in many mental disorders: α4β2- and α7-nAChRs are downregulated in AD [15], schizophrenia [91], and in autistic spectrum disorders [92,93], whereas upregulation of α7-nAChRs was shown in bipolar disorder [94], and upregulation or downregulation of α4β2-nACRs was revealed in obesity [95] or PD [15], respectively. The gene discussed is CHRNA7; the disease is obesity due to melanocortin 4 receptor deficiency.