The effect of nimodipine on memory loss following naloxone-induced morphine withdrawal in object recognition

We have previously evaluated the effect of nimodipine, L-type calcium channel blocker, on memory loss during spontaneous morphine withdrawal. In the present study the effect of nimodipine on memory loss in naloxone-induced morphine withdrawal mice was investigated. Mice were made dependent by increasing doses of morphine for three days. Object recognition task that was used for evaluation of memory performance comprised of three sections: 15 min habitation, 12 min first trial and 5 min test trial. Naloxone was injected 3 h after the administration of the last dose of morphine. Recognition index was evaluated 20 min after naloxone injection. Nimodipine was administrated in repeated form (1, 5 and 10 mg/kg) with daily doses of morphine or as a single injection (5 and 10 mg/kg) on the last day. Both acute and repeated treatments with nimodipine prevented the memory impairment in naloxone-induced morphine withdrawal mice (P<0.05 comparison of acute and repeated treatment data with their corresponding control values). Corticosterone concentration was significantly increased in the brain and blood of the mice during withdrawal. Pretreatment with nimodipine, however, decreased the corticosterone concentration in both brain and blood. The present study showed that nimodipine prevents intense memory loss following naloxone-induced morphine withdrawal.