Histamine and histamine receptors in Tourette syndrome and other neuropsychiatric conditions.

The potential contributions of dysregulation of the brain's histaminergic modulatory system to neuropsychiatric disease, and the potential of histamine-targeting medications as therapeutic agents, are gradually coming into focus. The H3R receptor, which is expressed primarily in the central nervous system, is a promising pharmacotherapeutic target. Recent evidence for a contribution of histamine dysregulation to Tourette syndrome and tic disorders is particularly strong; although specific mutations in histamine-associated genes are rare, they have led to informative studies in animal models that may pave the way for therapeutic advances. A controlled study of an H3R antagonist in Tourette syndrome is ongoing. Preclinical studies of H3R antagonists in schizophrenia, attention deficit disorder, and narcolepsy have all shown promise. Recently reported controlled studies have been disappointing in schizophrenia and attention deficit disorder, but the H3R antagonist pitolisant shows promise in the treatment of narcolepsy and excessive daytime sleepiness and is currently under regulatory review for these conditions. This article is part of the Special Issue entitled 'Histamine Receptors'.