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Repeated administrations of dopamine receptor agents affect lithium-induced state-dependent learning in mice

Department of Pharmacology, School of Medicine and Iranian National Centre 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 zarinmr{at}ams.ac.ir

F Madadi

Department of Basic Sciences, Tehran North Unit, Azad University, Tehran, Iran

S Ahmadi

Department of Biological Science & Biotechnology, Faculty of Science, University of Kurdistan, Sanandaj, Iran

Abstract

The influence of repeated administration of dopamine receptor agents on the effect of lithium on lithium-induced state-dependent learning was examined in mice. Immediate post-training intraperitoneal (i.p.) administrations of lithium (10 and 20 m/kg) decreased the step-down latency of a single-trial inhibitory avoidance task. This was fully or partly reversed by pre-test administration of the same doses of the drug, with maximum response at the dose of 10 mg/kg, suggesting state-dependent learning was induced by lithium. Here, it has also been shown that repeated intracerebroventricular administrations of a mixed D1/D2 dopamine receptors agonist apomorphine (once daily injections of 0.5 µg/mouse for three consecutive days followed by five days of no drug treatment) increased the effect of lower doses of pre-test lithium (1.25, 2.5 and 5 mg/kg, i.p.) on the reinstatement of the step-down latency decreased by post-training lithium (10 mg/kg). On the contrary, not only repeated administrations of the dopamine D1 receptor antagonist SCH 23390 (0.5 and 1 µg/mouse) but also the dopamine D2 receptor antagonist sulpiride (0.3 and 1 µg/mouse) disrupted the state-dependent learning induced by lithium. These results suggest that state-dependent learning induced by lithium may be altered by repeated pretreatment of dopamine receptor agents.

Key Words: apomorphine • lithium • memory • mouse • SCH23390 • sulpiride

This version was published on August 1, 2009

Journal of Psychopharmacology, Vol. 23, No. 6, 645-651 (2009)
DOI: 10.1177/0269881108093926


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