The roles of histamine H1 receptors on cognition

Abstract

Histamine neurons are located exclusively in the posterior hypothalamus, from where they project diffusely to all regions of brain. Neuronal histamine has been implicated in a variety of brain functions including wakefulness, learning and memory [1]. Although it is well known that sedative antihistamines induce cognitive decline in humans through blockage of H1 receptor [2], both facilitatory and inhibitory effects of neuronal histamine on learning and memory have been described in animal behavioral studies [3, 4]. Histaminergic neurotransmission has been also implicated in pathophysiology of stress-related psychiatric diseases [5]. Although several atypical antipsychotics are potent H1 antagonists [6], the clinical signifi cance of interaction between atypical antipsychotics and H1 receptors is still unknown. The aim of this study was to investigate the role of histamine H1 receptors on cognition in normal conditions using H1 receptor gene knockout mice (H1KO). We also investigated the effects of H1 receptor blockade on social isolation-induced behavioral and neurochemical changes in H1KO mice and their wild-type (WT) mice.