Zantac Research Today is a free monthly online journal that collates and summarizes the latest research about Zantac, including details on ranitidine, side-effects, allergic reactions, information.

The effects of histaminergic agents in the dorsal hippocampus of rats in the elevated plus-maze test of anxiety.

Zarrindast MR, Torabi M, Rostami P, Fazli-Tabaei S

Department of Pharmacology, School of Medicine and Iranian National Center for Addiction Studies, Tehran University of Medical Sciences, Tehran, Iran; Institute for Studies in Theoretical Physics and Mathematics, School of Cognitive, Sciences, Tehran, Iran; Institute for Cognitive Science Studies, Tehran, Iran.

High levels of histamine are found in the hippocampus. The central histamine system is involved in many physiological behavioural processes including anxiety-related behaviours both in animals and humans. In the present study, we investigated the effects of intra-hippocampal CA1 (intra-CA1) microinjection of histaminergic agents on anxiety-related behaviours in rats, using elevated plus-maze test of anxiety. Intra-CA1 administration of histamine (at the dose of 10 mug/rat) increased open arm time (%OAT) and open arm entry (%OAE) but not locomotor activity, thus showing an anxiolytic response. Intra-CA1 microinjection of pyrilamine (H(1) receptor antagonist; at the doses of 10, 20 and 40 mug/rat) in combination with histamine (10 mug/rat) showed a decrease in the %OAT and %OAE. Higher dose of the antagonist (40 mug/rat) by itself increased both %OAT and %OAE, but not locomotor activity, indicating an anxiolytic effect. Intra-CA1 microinjection of ranitidine (H(2) receptor antagonist), at the doses of 10, 20 and 40 mug/rat, also reduced the histamine response. Furthermore, the H(2) receptor antagonist by itself reduced %OAT and %OAE without affecting locomotor activity. The results may indicate an anxiogenic effect for the antagonist. Our results showed that histamine may modulate anxiety via H(1) and H(2) receptors in the CA1 region of hippocampus of the rat.

Published 17 November 2006 in Pharmacol Biochem Behav.
Full-text of this article is available online (may require subscription).

© 2004-2008 Zantac Research Today. All Rights Reserved.