HTR5A and early-onset autosomal dominant Alzheimer disease: We can trace back to the scientific works based on the “Guinea pig,” e.g., “The stimulation of 5-ht(1E) receptors and subsequent inhibition of adenylate cyclase activity in the DG suggests that 5-ht(1E) receptors may mediate regulation of hippocampal activity by 5-HT, making it a possible drug target for the treatment of neuropsychiatric disorders characterized by memory deficits (such as Alzheimer's disease) or as a target for the treatment of temporal lobe epilepsy (Klein and Teitler, 2012).”