The effect of dopamine D2 receptors of the dorsal hippocampus on the Histamine-induced anxiety behavior in mice

High levels of histamine and dopamine are found in the hippocampus. Furthermore, interaction between histamine and dopaminergic D2 receptors has been demonstrated in the modulation of some behaviors. In the present study, interaction between histamine and dopaminergic D2 receptor in the dorsal hippocampus in the anxiety behavior has been investigated. In this experimental study, 220 adult male NMRI mice were anesthetized and then placed in a stereotaxic apparatus. Two stainless-steel cannuale were placed in the CA1 region of hippocampus. The elevated plus maze test has been used to test anxiety-like behaviors. Two and one-way analyses of variance (ANOVAs) followed by LSD test, were used for analysis of the data. All experiments were performed in accordance with institutional guidelines for animal care and use. Intra-CA1 injection of histamine and dopamine D2 agonist (quinpirole) and antagonist (sulpiride) induced anxiety. Intra-CA1 injection quinpirole or sulpiride 2 minute after effective dose of histamine inhibited anxiogenic effects of histamine. It seems that both histamine and dopaminergic D2 receptors not only play a part in the modulation of anxiety in the dorsal hippocampus of mice but also have demonstrated a complex interaction.