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Updated: Jul 14, 2026
Assessment of Morphine-induced Hyperalgesia and Analgesic Tolerance in Mice Using Thermal and Mechanical Nociceptive Modalities
Published on: July 29, 2014
Effects of morphine and its withdrawal on Y-maze spatial recognition memory in mice
Unlabelled:
Effects of morphine on acquisition and retrieval of memory have been proven in the avoidance paradigms. In present study, we used a two-trial recognition Y-maze to test the effects of acute morphine and morphine withdrawal on spatial recognition memory. The Y-maze is based on the innate tendency of rodents to explore novel environments and therefore avoid punishment and reward.
Results:
1) Pre-training morphine 10 mg/kg impaired the recognition spatial memory of acquisition after a 1 h inter-trial interval (ITI), whereas morphine 2.5, 5 and 10 mg/kg showed impairment after 2 h ITI. 2) Pre-retention morphine 5, 10 mg/kg disrupted the retrieval of memory after 1 h ITI. 3) Morphine 5 and 10 mg/kg caused hyper-locomotor activity depending on the state. 4) Mice withdrawn from morphine 40 mg/kg but not 10 mg/kg for 3 days showed amnesia in Y-maze. Our data suggested that acute morphine impaired the acquisition and retrieval of spatial recognition memory and increased the locomotor activity in the Y-maze depending on the dose and state. Moreover, withdrawal from chronic morphine also impaired acquisition in the Y-maze depending on the dose and state.
Insights
Acute morphine impairs spatial recognition memory acquisition and retrieval in mice. Morphine withdrawal also negatively impacts memory, highlighting the drug's significant effects on cognitive function.
Area of Science:
- Neuroscience
- Pharmacology
- Cognitive Science
Background:
- Morphine's effects on memory are established in avoidance paradigms.
- Spatial recognition memory relies on rodents' innate exploration tendencies.
Purpose of the Study:
- To investigate acute morphine and withdrawal effects on spatial recognition memory using a Y-maze.
- To assess impacts on memory acquisition and retrieval.
Main Methods:
- Utilized a two-trial recognition Y-maze in mice.
- Administered acute morphine pre-training and pre-retention at varying doses.
- Examined memory performance after 1-hour and 2-hour inter-trial intervals (ITIs).
- Assessed locomotor activity.
- Evaluated memory in mice withdrawn from chronic morphine.
Main Results:
- Acute morphine (10 mg/kg) impaired acquisition memory after 1h ITI; higher doses (2.5-10 mg/kg) impaired it after 2h ITI.
- Morphine (5-10 mg/kg) disrupted memory retrieval after 1h ITI.
- Morphine (5-10 mg/kg) induced dose-dependent hyper-locomotor activity.
- Withdrawal from high-dose morphine (40 mg/kg) for 3 days caused amnesia.
Conclusions:
- Acute morphine impairs both acquisition and retrieval of spatial recognition memory.
- Morphine increases locomotor activity in a dose- and state-dependent manner.
- Withdrawal from chronic morphine also impairs spatial recognition memory acquisition.
