Neuroscience research
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Neuroscience research · Jan 2011
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. ⋯ 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.
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Neuroscience research · Jan 2011
Intrathecally administered Sema3A protein attenuates neuropathic pain behavior in rats with chronic constriction injury of the sciatic nerve.
Semaphorins, one of the repulsive axonal guidance factors during development, are produced under pathological conditions in adult animals. In the neuropathic pain state associated with peripheral nerve injury, synaptic reorganization occurs in spinal cord dorsal horn. In the present study, we investigated the roles of intrathecal administration of Sema3A, a secreted semaphorin, in the spinal cord of chronic constriction injury (CCI) model rat. ⋯ Immunohistochemistry revealed that Sema3A partially restored the decrease of isolectin B4-positive unmyelinated nerve terminals in lamina II of the ipsilateral dorsal horn of CCI rats. Contrary to our expectations, Sema3A did not change the distribution of myelinated fibers in lamina II at 7 days after CCI. Those results suggested that the suppressive role for Sema3A in the development of neuropathic pain associated with peripheral nerve injury in adult rats, which seemed to be independent from prevention of the myelinated fiber sprouting into lamina II.
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Neuroscience research · Jan 2011
Involvement of central amygdala NMDA receptor mechanism in morphine state-dependent memory retrieval.
In the current study, the effects of intra-central amygdala (CeA) administration of N-methyl-D-aspartate (NMDA) and its competitive antagonist, D-2-amino-5-phosphonopentanoic acid (D-AP5), on morphine state-dependent memory retrieval were investigated. Post-training subcutaneous (s.c.) administration of different doses of morphine (0.5, 2.5, 5 and 7.5 mg/kg) dose-dependently impaired memory. The response induced by post-training morphine (7.5 mg/kg) was reversed by pre-test administration of this drug (5 and 7.5 mg/kg), indicating morphine state-dependent memory retrieval. ⋯ Pre-test intra-CeA administration of D-AP5 (0.1-1.0 μg/rat) decreased morphine state-dependent memory retrieval. However, pre-test administration of D-AP5 (0.1-1 μg/rat) alone decreased memory retrieval, but restored post-training morphine-induced amnesia. In conclusion, our results suggest which CeA may be potentially critical for morphine state-dependent memory retrieval and that CeA NMDA receptor mechanism(s) interact with the opiodergic system in the modulation of morphine state-dependent memory retrieval.