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Possible involvement of µ-opioidreceptors in effect of lithium on inhibitory avoidance response in mice
1 Department of Pharmacology, School of Medicine and Iranian National
Center forAddiction Studies, Tehran University of Medical Sciences; School of
Cognitive Science, Institute for Studies Theoretical Physicsand Mathematics and
Institute for Cognitive Science Studies, Tehran, Iran.
* To whom correspondence should be addressed.
In the present study, effects of intracerebroventricular (i.c.v.) injectionsof _-opioid receptor agonist and antagonist on lithium state-dependencywere investigated. For memory assessment, a one-trial step-downinhibitory avoidance task was used in adult male NMRI mice. Intraperitoneal(i.p.) administration of lithium (10mg/kg) after training impairedmemory when retrieval was tested 24 h later. The memory impairmentwas reversed by pretest administration of the same dose of lithium, suggestingstate-dependency induced by lithium. In addition, i.c.v. administrationof both lithium (2 and 4_g/mouse, i.c.v.) and morphine (3 and6_g/mouse, i.c.v.) before the test reversed memory impairment inducedby post-training lithium (10mg/kg, i.p.). On the other hand, pretestadministration of naloxone (1 and 2mg/kg) which had no effects aloneon inhibitory avoidance response, prevented the improving effects ofboth morphine (3_g/mouse, i.c.v.) and lithium (2_g/mouse, i.c.v.) onmemory retrieval. The results suggest that the _-opioid receptors in thecentral nervous system may be involved in the retrieval of lithium statedependentlearning. Key Words: lithium, morphine, naloxone, state-dependency, memory retrieval, mouse
First published on January 21, 2008, doi:10.1177/0269881107083848 |
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