Influence of three-day morphine-treatment upon impairment of memory consolidation induced by cannabinoid infused into the dorsal hippocampus in rats.
In the present study, the effects of morphine treatment upon reduction of memory consolidation by post-training administration of the non-selective cannabinoid CB(1)/CB(2) 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 0.5 μg/rat) shortened the step-through latency, which suggested impaired memory consolidation. The deleterious effect of WIN55,212-2 (0.5 μg/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 mu-receptor antagonist, naloxone, and the dopamine D(2) receptor antagonist, sulpiride, but not by the D(1) receptor antagonist, SCH 23390, when administered prior to each morphine injection. The results have suggested that subchronic morphine treatment may cause mu-opioid and D(2) receptor sensitization, which in turn prevents impairment of memory consolidation induced by WIN55,212-2.
Zarrindast
Mohammad Reza
MR
Department of Neuroscience, School of Advanced Medical Technologies, Tehran University of Medical Sciences, Tehran, Iran. zarinmr@ams.ac.ir
Navaeian
Majid
M
Nasehi
Mohammad
M
D000647:Amnesia / Q000139:chemically induced; D000700:Analgesics / Q000008:administration & dosage* / Q000009:adverse effects; D000818:Animals; D001362:Avoidance Learning / Q000187:drug effects; D001552:Benzazepines / Q000008:administration & dosage; D048588:Benzoxazines / Q000008:administration & dosage* / Q000009:adverse effects; D056547:CA1 Region, Hippocampal / Q000187:drug effects* / Q000378:metabolism; D018492:Dopamine Antagonists / Q000008:administration & dosage; D065127:Dopamine D2 Receptor Antagonists; D008297:Male; D008568:Memory / Q000187:drug effects*; D008569:Memory Disorders; D009020:Morphine / Q000008:administration & dosage* / Q000378:metabolism; D009025:Morpholines / Q000008:administration & dosage* / Q000009:adverse effects; D009270:Naloxone / Q000494:pharmacology; D009281:Naphthalenes / Q000008:administration & dosage* / Q000009:adverse effects; D051381:Rats; D017208:Rats, Wistar; D043884:Receptor, Cannabinoid, CB1 / Q000819:agonists; D043885:Receptor, Cannabinoid, CB2 / Q000819:agonists; D017447:Receptors, Dopamine D1 / Q000037:antagonists & inhibitors; D017450:Receptors, Opioid, mu / Q000037:antagonists & inhibitors; D013469:Sulpiride / Q000008:administration & dosage; D013997:Time Factors
D000700:Analgesics; D001552:Benzazepines; D048588:Benzoxazines; D018492:Dopamine Antagonists; D065127:Dopamine D2 Receptor Antagonists; D009025:Morpholines; D009281:Naphthalenes; D043884:Receptor, Cannabinoid, CB1; D043885:Receptor, Cannabinoid, CB2; D017447:Receptors, Dopamine D1; D017450:Receptors, Opioid, mu; C534628:SCH 23390; D009270:Naloxone; C070417:(3R)-((2,3-dihydro-5-methyl-3-((4-morpholinyl)methyl)pyrrolo-(1,2,3-de)-1,4-benzoxazin-6-yl)(1-naphthalenyl))methanone; D009020:Morphine; D013469:Sulpiride