Interaction Between Nitric Oxide and Histaminergic H1 Receptor of Dorsal Hippocampus in the Elevated Plus-Maze of Anxiety

Nitric oxide and histamine H1 receptors influence anxiety-like behaviors. Furthermore، interaction between nitric oxide and histamine H1 receptors has been demonstrated in the modulation of some behavior. The present study was designed to evaluate the interactions between pyrilamine، aH1 receptor antagonist and nitric oxide systems in the CA1 brain region of the mice using the plus-maze test. In this experimental study، 136 adult male NMRI mice were anesthetized with ketamine and xylazine and two cannuale were inserted stereotaxically into the CA1 region of the dorsal hippocampus. After 1 week recovery، the elevated plus maze test was used to test the anxiety-like behaviors. Intra-CA1 injection of pyrilamine induced anxiety. Intra-CA1 injection L-arginine (0. 1 and 0. 5 µg/mouse) or L-NAME (5، 10 ng/mouse) 2 min after befor effective dose of pyrilamine (9 µg/mouse) inhibited anxiogenic effects of pyrilamine. These results show that there are complex interactions between histamine H1 receptors and nitric oxide system that affect anxiety behaviors in the CA1 region of dorsal hippocampus. Activation or inhibition of nitric oxide system inhibits anxiogenic response of pyrilamine in the dorsal hippocampus.