introduction: activation of n-methyl-d-aspartate (nmda) glutamate receptors in the nucleus accumbens is a component of drug-induced reward mechanism. in addition, nmda receptors play a major role in brain reward system and activation of these receptors can change firing pattern of dopamine neurons. blockade of glutamatergic neurotransmission reduces the expression of conditioned place preferenc...

Existence of long-term drug-associated memories may be a crucial factor in drug cravings and relapse. RACK1 plays a critical role in morphine-induced reward. In the present study, we used conditioned place preference (CPP) to assess the acquisition and maintenance of morphine conditioned place preference memory. The hippocampal protein level of RACK1 and synaptic quantitation were evaluated by ...

BACKGROUND Tapentadol prolonged release (PR) is effective and well tolerated for chronic osteoarthritis, low back, and diabetic peripheral neuropathic pain. OBJECTIVES To evaluate the efficacy and tolerability of tapentadol PR compared with placebo and morphine controlled release (CR) for managing moderate to severe chronic malignant tumor-related pain. STUDY DESIGN Randomized-withdrawal, p...

In France, during the 1990s, there have been some rapid developments in the treatment of opioid addiction with the introduction of legal substitution agents. Originally, some patients were treated with morphine sulfate, but this was superseded by high dose buprenorphine (Subutex(R)) and methadone. This resulted in those patients originally treated with morphine being transferred to either of th...

The antinociceptive and ventilatory effects of morphine and other opioid agonists were determined in three rhesus monkeys during a period of morphine maintenance, as well as before and after the chronic exposure to morphine. Before the onset of the daily dosing regimen, morphine increased tail-withdrawal latencies from 50 degrees C water, with an ED50 of 6.4 +/- 2.1 mg/kg. Daily injection of 3....

In morphine tolerance a key question that remains to be answered is whether mu-opioid receptor (MOPr) desensitization contributes to morphine tolerance, and if so by what cellular mechanisms. Here we demonstrate that MOPr desensitization can be observed in single rat brainstem locus coeruleus (LC) neurons following either prolonged (> 4 h) exposure to morphine in vitro or following treatment of...

Previously we reported that prenatal exposure to morphine twice daily during gestation decreases proenkephalin levels in adult progeny within the brain, including the dentate gyrus, and alters mu and delta opioid receptors in the hippocampal CA3 region. The lateral aspect of the perforant path contains and releases enkephalin-derived opioid peptides, and induction of long-term potentiation (LTP...

Protein kinase C (PKC) is involved in intra-cellular signal transduction in various physiological and pathological processes including substance abuse. In the present study, the role of PKC in morphine-induced rewarding memory was investigated using the conditioned place preference (CPP) model. We found a significant translocation of PKCs from cytosol to membrane component in nucleus accumbens ...