Cognitive involvement by negative modulation of histamine H2 receptors in passive avoidance task in mice.

In this study, the intracerebroventricular administration of 4-methylhistamine (3 and 10 μg/head), a histamine H 2 receptor agonist, shortened the step-through latency in the retention trial using a step-through passive avoidance task in mice. This deteriorating effect of 4-methylhistamine (3 μg/head) was clearly antagonized by pretreatment with zolantidine (10 mg/kg, i.p.), a histamine H 2 receptor antagonist, 20 min fefore an acquisition trial. Zolantidine alone at the dose tested had no effect. Thus, it is likely that activation of histamine H 2 receptors has a deteriorating effect on avoidance learning in mice. The present results indicate the cognitive involvement by negative modulation of histamine H 2 receptors in passive avoidance task in mice.