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IPM
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“School of Cognitive Sciences”

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Paper   IPM / Cognitive Sciences / 12171
School of Cognitive Sciences
  Title:   Influence of three-day morphine-treatment upon impairment of memory consolidation induced by cannabinoid infused into the dorsal hippocampus in rats
  Author(s): 
1.  Mohammad Reza Zarrindast
2.  Majid Navaeian
3.  Mohammad Nasehi
  Status:   Published
  Journal: Neuroscience Research
  Vol.:  69
  Year:  2011
  Pages:   51-59
  Supported by:  IPM
  Abstract:
In the present study, the effects of morphine treatment upon reduction of memory consolidation by posttraining administration of the non-selective cannabinoid CB1/CB2 receptor agonist, WIN55,212-2, into the dorsal hippocampus (intra-CA1) have been investigated in rats. Step-through inhibitory avoidance apparatus was used to test memory retrieval, which was made of two white and dark compartments. In training day, electric shocks were delivered to the grid floor of the dark compartment. On the test day, the animal was placed in the white compartment and allowed to enter the dark compartment. The latency with which the animal crossed into the dark compartment was recorded as memory retrieval. Morphine was injected subcutaneously (S.C.), once daily for three days, followed by a five day morphine-free period before training. Bilateral post-training intra-CA1 infusions of WIN55,212-2 (0.25 and 0.5g/rat) shortened the step-through latency, which suggested impaired memory consolidation. The deleterious effect of WIN55,212-2 (0.5g/rat) was prevented in rats previously injected with morphine (10 mg/kg/day�3 days, S.C.). Prevention of the WIN55,212-2-induced amnesic-like effect was counteracted by the mureceptor antagonist, naloxone, and the dopamine D2 receptor antagonist, sulpiride, but not by the D1 receptor antagonist, SCH 23390, when administered prior to each morphine injection. The results have suggested that subchronic morphine treatment may cause mu-opioid and D2 receptor sensitization, which in turn prevents impairment of memory consolidation induced by WIN55,212-2.

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