Placebo-induced expectancies have been shown to decrease pain in a manner reversible by opioid antagonists, but little is known about the central brain mechanisms of opioid release during placebo treatment. This study examined placebo effects in pain by using positron-emission tomography with [(11)C]carfentanil, which measures regional mu-opioid receptor availability in vivo. Noxious thermal st...

Considerable evidence suggests that in instrumental conditioning rats learn the relationship between actions and their consequences, or outcomes. Such goal-directed actions are sensitive to changes in outcome value. The present study assessed the role of the endogenous opioid system in goal-directed reward learning. In two experiments, rats were trained to lever press for food pellets either un...

Due to the criminalization of drug use and addiction, opioid use disorder is overrepresented in incarcerated populations. Decades of evidence supports opioid agonist therapy as a highly effective treatment that improves clinical outcomes and reduces illicit opioid use, overdose death, and cost. Opioid agonist therapy has been both studied within correctional facilities and initiated prerelease....

Mu opioid receptors are critical for heroin dependence, and A118G SNP of the mu opioid receptor gene (OPRM1) has been linked with heroin abuse. In our population of European Caucasians (n = 118), approximately 90% of 118G allelic carriers were heroin users. Postmortem brain analyses showed the OPRM1 genotype associated with transcription, translation, and processing of the human striatal opioid...

The opioid system is well-known for its role in modulating nociception and addiction development. However, there are premises that the endogenous may also affect blood pressure. main goal of present study was to determine impact different activity pharmacological blockade on Moreover, we examined vascular function hyper- hypoactive states modification. In our study, used two mouse lines which d...

Opioid-induced constipation (OIC) is a common side effect of opioid pharmacotherapy for the management of pain because opioid agonists bind to µ-opioid receptors in the enteric nervous system (ENS). Naloxegol, a polyethylene glycol derivative of naloxol, which is a derivative of naloxone and a peripherally acting µ-opioid receptor antagonist, targets the physiologic mechanisms that cause OIC. P...

OBJECTIVE OA is the most common joint disease, affecting 10-15% of people over 60 years of age. However, up to 40% of individuals with radiologic damage are asymptomatic. The purpose of this study was to assess the role of the endogenous opioid system in delaying the onset of pain in a murine model of osteoarthritis (OA). METHODS Osteoarthritis was induced by transection of the medial menisco...

The opioid peptides and receptors have prominent roles in pain transmission and reward mechanisms in mammals. The evolution of the opioid receptors has so far been little studied, with only a few reports on species other than tetrapods. We have investigated species representing a broader range of vertebrates and found that the four opioid receptor types (delta, kappa, mu, and NOP) are present i...

introduction: association between single-nucleotide polymorphisms (snps) in mu opioid receptor gene and drug addiction has been shown in various studies. here, we have evaluated the existence of polymorphisms in exon 3 of this gene in iranian population and investigated the possible association between these mutations and opioid addiction.  methods: 79 opioid-dependent subjects (55 males, 24 fe...

BACKGROUND Aripiprazole is an antipsychotic drug used to treat schizophrenia and related disorders. Our previous study showed that this compound also induces antinociceptive effects. The present study aimed to assess the participation of the opioid system in this effect. METHODS Male Swiss mice were submitted to paw pressure test and hyperalgesia was induced by intraplantar injection of prost...