Possible involvement of μ-opioid receptors in effect of lithium on inhibitory avoidance response in mice

• Published in: Journal of psychopharmacology (Oxford) 2008-11, Vol.22 (8), p.865-871
• Main Authors: Zarrindast, M-R., Lahmi, A., Ahamadi, S.
• Format: Article
• Language: English
• Subjects: Animals; Antimanic Agents - pharmacology; Avoidance Learning - drug effects; Biological and medical sciences; Cognitive ability; Lithium; Lithium Chloride - pharmacology; Male; Medical sciences; Memory; Memory Disorders - chemically induced; Mice; Morphine - pharmacology; Naloxone - pharmacology; Narcotics; Neuropharmacology; Pharmacology. Drug treatments; Psychoanaleptics: cns stimulant, antidepressant agent, nootropic agent, mood stabilizer; Psychoanaleptics: cns stimulant, antidepressant agent, nootropic agent, mood stabilizer..., (alzheimer disease); Psychology. Psychoanalysis. Psychiatry; Psychopharmacology; Receptors, Opioid, mu - physiology
• ISSN: 0269-8811; 1461-7285
• DOI: 10.1177/0269881107083848

In the present study, effects of intracerebroventricular (i.c.v.) injections of μ-opioid receptor agonist and antagonist on lithium state-dependency were investigated. For memory assessment, a one-trial step-down inhibitory avoidance task was used in adult male NMRI mice. Intraperitoneal (i.p.) administration of lithium (10 mg/kg) after training impaired memory when retrieval was tested 24 h later. The memory impairment was reversed by pretest administration of the same dose of lithium, suggesting state-dependency induced by lithium. In addition, i.c.v. administration of both lithium (2 and 4 μg/mouse, i.c.v.) and morphine (3 and 6 μg/mouse, i.c.v.) before the test reversed memory impairment induced by post-training lithium (10 mg/kg, i.p.). On the other hand, pretest administration of naloxone (1 and 2 mg/kg) which had no effects alone on inhibitory avoidance response, prevented the improving effects of both morphine (3 μg/mouse, i.c.v.) and lithium (2 μg/mouse, i.c.v.) on memory retrieval. The results suggest that the μ-opioid receptors in the central nervous system may be involved in the retrieval of lithium state-dependent learning.