CHRNA4 and attention deficit-hyperactivity disorder: In fact, as nAChRs are functionally involved in many essential CNS cellular mechanisms, including learning, anxiety, memory, and cognitive function, several nAchR ligands have been developed for the treatment of many pathologies, such as AD, attention deficit hyperactivity disorder (ADHD), anxiety, Parkinson’s disease, inflammatory bowel disorder, schizophrenia, depression, and many others [22].