Possible involvement of mu-opioid receptors in effect of lithium on inhibitory avoidance response in mice.
In the present study, effects of intracerebroventricular (i.c.v.) injections of mu-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 microg/mouse, i.c.v.) and morphine (3 and 6 microg/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 microg/mouse, i.c.v.) and lithium (2 microg/mouse, i.c.v.) on memory retrieval. The results suggest that the mu-opioid receptors in the central nervous system may be involved in the retrieval of lithium state-dependent learning.
Zarrindast
M-R
MR
Department of Pharmacology, School of Medicine and Iranian National Center for Addiction Studies, Tehran University of Medical Sciences, Institute for Study Theoretical Physics and Mathematics, Tehran, Iran. zarinmr@ams.ac.ir
Lahmi
A
A
Ahamadi
S
S
D000818:Animals; D018692:Antimanic Agents / Q000494:pharmacology*; D001362:Avoidance Learning / Q000187:drug effects*; D018021:Lithium Chloride / Q000494:pharmacology*; D008297:Male; D008569:Memory Disorders / Q000139:chemically induced; D051379:Mice; D009020:Morphine / Q000494:pharmacology; D009270:Naloxone / Q000494:pharmacology; D017450:Receptors, Opioid, mu / Q000502:physiology*
D018692:Antimanic Agents; D017450:Receptors, Opioid, mu; D009270:Naloxone; D009020:Morphine; D018021:Lithium Chloride