Histamine H 1 receptors in dentate gyrus-projecting cholinergic neurons of the medial septum suppress contextual fear retrieval in mice.

Fear memory is essential for survival and adaptation, yet excessive fear memories can lead to emotional disabilities and mental disorders. Despite previous researches have indicated that histamine H 1 receptor (H 1 R) exerts critical and intricate effects on fear memory, the role of H 1 R is still not clarified. Here, we show that deletion of H 1 R gene in medial septum (MS) but not other cholinergic neurons selectively enhances contextual fear memory without affecting cued memory by differentially activating the dentate gyrus (DG) neurons in mice. H 1 R in cholinergic neurons mediates the contextual fear retrieval rather than consolidation by decreasing acetylcholine release pattern in DG. Furthermore, selective knockdown of H 1 R in the MS is sufficient to enhance contextual fear memory by manipulating the retrieval-induced neurons in DG. Our results suggest that H 1 R in MS cholinergic neurons is critical for contextual fear retrieval, and could be a potential therapeutic target for individuals with fear-related disorders.