HTR6 and early-onset autosomal dominant Alzheimer disease: Predominantly, lines of evidence have indicated memory and learning ability improvement effects, useful in mild and moderate form of Alzheimer’s disease (AD) and age-related cognitive decline as well as antidepressant-like, anxiolytic-like, and anti-obesity properties for 5-HT6R antagonists, while similar effects has also been confirmed for some 5-HT6R agonists [3,4,6,7,8].