Interaction between apomorphine and histaminergic system of mouse dorsal hippocampus in the elevated plus-maze test of anxiety

Histaminergic and dopaminergic systems influence anxiety-related behavior. Furthermore, interaction between histaminergic and dopaminergic receptors has been demonstrated in the modulation of some behaviors in the hippocampus. In the present study, the interaction between histaminergic and dopaminergic receptors of dorsal hippocampus in the anxiety-related behavior has been evaluated. This experimental study was carried out on 140 male NMRI mice. Mice were anesthetized with intra-peritoneal injection of ketamine hydrochloride plus xylazine and then placed in a stereotaxic apparatus. Two cannuales were placed in the CA1 region of hippocampus. All animals were allowed to recover for one week before the beginning of the behavioral testing. The elevated plus-maze test was used to evaluate anxiety-related behaviors. One-way analysis of variance (ANOVA) followed by LSD test were done for the statistical analysis of the data. All experiments were conducted in accordance with institutional guidelines for animal care and use. Intra-CA1 injection of histamine (10 µg/mouse) or apomorphine (0.1 and 0.3 µg/mouse) 5 min before testing induced anxiety. Intra-CA1 injection of apomorphine (0.01 and 0.1 µg/mouse) 2 min before the effective dose of histamine (10 µg/mouse) inhibited the anxiogenic effects of histamine. It seems that both histaminergic and dopaminergic system not only play a role in the modulation of anxiety in the dorsal hippocampus of mice but also demonstrate a complex interaction as well.