Effects of pre-training morphine on spatial memory acquisition and retrieval in mice

• Published in: Physiology & behavior Vol. 104; no. 5; pp. 754 - 760
• Main Authors: Zhu, Feng, Yan, Chun-xia, Zhao, Yan, Zhao, Yang, Li, Ping-ping, Li, Sheng-bin
• Format: Journal Article
• Language: English
• Published: Amsterdam Elsevier Inc 24.10.2011; Elsevier
• Subjects: Analysis of Variance; Animals; Behavior, Animal; Behavioral psychophysiology; Biological and medical sciences; brain; Conditioning, Operant - drug effects; Cues; Dose-Response Relationship, Drug; Drug Administration Schedule; Exploratory Behavior - drug effects; Fundamental and applied biological sciences. Psychology; Male; Maze Learning - drug effects; memory; Memory acquisition; Memory retrieval; Mental Recall - drug effects; Mice; Mice, Inbred C57BL; Morphine; Morphine - pharmacology; Morris water maze; motivation; Motivation - drug effects; Naloxone; Naloxone - pharmacology; Narcotic Antagonists - pharmacology; narcotics; Narcotics - pharmacology; Psychiatry; Psychology. Psychoanalysis. Psychiatry; Psychology. Psychophysiology; Reaction Time - drug effects; Space Perception - drug effects; Spatial memory; Time Factors; Memory retrieval; Morphine; Naloxone; Morris water maze; Memory acquisition; Spatial memory; Morphinan derivatives; Narcotic antagonist; Rodentia; Opiates; Space perception; Narcotic analgesic; Vertebrata; Mammalia; Acquisition process; Mouse; Animal; Perceptive learning
• ISSN: 0031-9384; 1873-507X
• DOI: 10.1016/j.physbeh.2011.07.014

The opioid system plays an important role in memory processess. Morphine mimics endogenous opioids by acting on opioid receptor in brain to regulate memory. However, the effects of morphine on spatial memory acquisition are controversial. Also, little evidence has suggested that morphine could affect the retrieval of spatial memory. In the current study, effects of pre-training morphine and naloxone on the acquisition vs. retrieval of spatial reference vs. working memory were examined using discrete water maze tasks in C57BL/6 mice. Pre-training morphine administration (7.5 and 15mg/kg, i.p.) impaired the acquisition of both spatial reference memory and working memory. Motivation to escape from the water maze was not affected by morphine. Pre-test morphine also inhibited the retrieval of spatial working memory but not reference memory. The effects of morphine on the acquisition and retrieval of spatial working memory were eliminated by naloxone pretreatment (1mg/kg). These results indicate that morphine could differentially modulate a variety of aspects of spatial memory and these effects are mediated by the mu-opioid receptor.