The nucleus accumbens is a terminal area of the mesolimbic dopaminergic system that arises in the ventral tegmental area. Opioids are thought to enhance dopaminergic activity in the nucleus accumbens by activating δ- and μ-opioid receptors in the ventral tegmental area. However, δ- and μ-opioid receptor agonists increase extracellular levels of accumbal dopamine when infused directly into the n...

Nociceptin/orphanin FQ (N/OFQ), a 17-amino-acid peptide, is an endogenous agonist whose receptor is similar in sequence to mu, delta and kappa opioid receptors. It has been reported that N/OFQ can block antinociceptive effects induced by opioid receptor agonists in the radiant heat tail-flick test and warm water tail-withdrawal test. The present study was designed to see the effect of N/OFQ on ...

PURPOSE We investigated what kinds of neurotransmitters are related with electroacupuncture (EA) analgesia in an arthritic pain model of rats. MATERIALS AND METHODS One hundred rats were assigned to six groups: control, EA, opioid, adrenergic, serotonin and dopamine group. A standardized model of inflammatory arthritis was produced by injecting 2% carrageenan into the knee joint cavity. EA wa...

Salvia divinorum is a hallucinogenic plant used by the Mazatec Indians of Mexico for traditional spiritual ceremonies. The active constituent, salvinorin A, induces profound hallucinations, however the biological mechanism for this action is not known. Affinity-binding studies suggest that the biologic activity of salvinorin A involves the kappa-opioid receptor. The purpose of this study was to...

Opioid drugs play important roles in the clinical management of pain, as well as in the development and treatment of drug abuse. The mu opioid receptor is the primary site of action for the most commonly used opioids, including morphine, heroin, fentanyl, and methadone. By sequencing DNA from 113 former heroin addicts in methadone maintenance and 39 individuals with no history of drug or alcoho...

Cebranopadol (trans-6'-fluoro-4',9'-dihydro-N,N-dimethyl-4-phenyl-spiro[cyclohexane-1,1'(3'H)-pyrano[3,4-b]indol]-4-amine) is a novel analgesic nociceptin/orphanin FQ peptide (NOP) and opioid receptor agonist [Ki (nM)/EC50 (nM)/relative efficacy (%): human NOP receptor 0.9/13.0/89; human mu-opioid peptide (MOP) receptor 0.7/1.2/104; human kappa-opioid peptide receptor 2.6/17/67; human delta-opi...

To characterize further the establishment of the opioid system during prenatal mouse development, we have examined the spatial and temporal expression patterns of m, k, and d opioid receptor mRNAs and find that the expression patterns of these mRNAs are distinct at all ages. Within the embryo, k is the first opioid receptor expressed, with transcripts detected in the gut epithelium as early as ...

Editor’s points † Genetic polymorphism in the m-opioid receptor can affect systemic opioid analgesia. † The effects of the A118G polymorphism on analgesia and pruritus after intrathecal fentanyl for labour analgesia were compared in two ethnically distinct populations. † While there was no effect of the genetic polymorphism, there was a marked effect of the ethnically distinct groups on duratio...

Opioids are a group of analgesic agents commonly used in clinical practice. There are three classical opioid receptors (DOP, KOP and MOP), while the novel NOP receptor is considered to be a non-opioid branch of the opioid receptor family. Opioids can act at these receptors as agonists, antagonists or partial agonists. Opioid agonists bind to G-protein coupled receptors to cause cellular hyperpo...

Spinal cord neurons can support a simple form of instrumental learning. In this paradigm, rats completely transected at the second thoracic vertebra learn to minimize shock exposure by maintaining a hindlimb in a flexed position. Prior exposure to uncontrollable shock (shock independent of leg position) disrupts this learning. This learning deficit lasts for at least 24h and depends on the NMDA...