The interaction between harmane and nicotinic receptors of dorsal hippocampus in a hole-board test of anxiety in mice

β-carboline alkaloids, such as harmane, are found in common plant-derived foodstuffs and plant-derived inhalation components of tobacco. In the present study, the involvement of dorsal hippocampus nicotinic receptor in the harmane effects on anxiety behavior has been evaluated. Mice were anesthetized with an intra-peritoneal injection of ketamine hydrochloride plus xylazine and then placed in a stereotaxic apparatus. Cannual were bilaterally implanted in the CA1 region of hippocampus. All animals were allowed to recover for 1 week before the beginning of the behavioral testing. The hole-board test was used to evaluate the anxiety-like behaviors. One-way analys was of variance so that Dunnett’s test was used to analyse data. All experiments were performed in accordance with institutional guidelines for animal care and use. Intraperitoneal injection of harmane decreased the number of head dip and locomotion (P<0.001). While bilateral intra-dorsal hippocampal injections of nicotine decreased the number of head dip (P<0.01), it had no effect on locomotor activity. Furthermore, intra-dorsal hippocampal injection of mecamylamine (nicotinic receptor antagonist) in the presence and absence of harmane had no effect on anxiety behavior and locomotion (P>0.05). harmane and nicotine not only display anxiogenic effects but also demonstrate a complex interaction. The findings also indicated that harmane induces anxiety via non-nicotinic receptors.