HRH3 and Alzheimer disease: By blocking centrally located histamine H3 receptors (H3Rs), which causes an increment in the release of brain neurotransmitters such as HA, ACh, DA, and norepinephrine, preclinical research suggested that H3R antagonists could potentially play a role in the therapeutic management of a variety of cognitive disorders, such as memory deficit, attention-deficit/hyperactivity disorder (ADHD), AD, and schizophrenia.