The ability of neuropeptide Y to potently stimulate food intake is dependent in part upon the functioning of mu and kappa opioid receptors. The combined use of selective opioid antagonists directed against mu, delta or kappa receptors and antisense probes directed against specific exons of the MOR-1, DOR-1, KOR-1 and KOR-3/ORL-1 opioid receptor genes has been successful in characterizing the pr...

BACKGROUND AND PURPOSE Adenylyl cyclase sensitization occurs on chronic agonist activation of mu-opioid receptors and is manifested by an increase in cAMP levels (overshoot) on challenge with antagonist. It has been proposed that a long lasting constitutively active receptor is formed on chronic mu-opioid exposure and that antagonists with inverse agonist activity rapidly return the receptor to...

PURPOSE OF REVIEW Recent studies highlighting between-opioid differences in patient outcomes, opioid receptor interactions and animal study findings implicating a 'fine control' mechanism underpinning potential diversity in opioid receptor signalling that could potentially be exploited to develop novel opioid analgesics with improved tolerability are reviewed. RECENT FINDINGS Recent clinical ...

Background Increased locomotor activity in response to the same stimulus is an index of behavioral sensitization observed in preclinical models of drug addiction and compulsive behaviors. Repeated administration of quinpirole, a D2/D3 dopamine agonist, induces locomotor sensitization. This effect is potentiated and accelerated by co-administration of U69593, a kappa opioid receptor agonist. The...

Opioid receptors, MORP, DORP and KORP, belong to the family A of G protein coupled receptors (GPCR), and have been found to modulate a large number of physiological functions, including mood, stress, appetite, nociception and immune responses. Exogenously applied opioid alkaloids produce analgesia, hedonia and addiction. Addiction is linked to alterations in function and responsiveness of all t...

Naltrexone, an opioid antagonist, has been used in clinical trials to treat alcoholism. As the opioid peptides beta-endorphin and enkephalin increase splenic NK cell function in laboratory animals, it is anticipated that naltrexone treatment will cause immunosuppression. However, we report in this study that chronic naltrexone administration in laboratory rats increases the cytolytic activity o...

Opioid treatment of pain is generally safe with 0.5% or less events from respiratory depression. However, fatalities are regularly reported. The only treatment currently available to reverse opioid respiratory depression is by naloxone infusion. The efficacy of naloxone depends on its own pharmacological characteristics and on those (including receptor kinetics) of the opioid that needs reversa...

A. The endogenous opioid system and natural reinforcement 1383 B. The endogenous opioid system and drugs of abuse 1387 C. Perspectives: extending studies to animal models of drug addiction 1393 IV. Genetic Manipulation of the Opioid System, Reinforcement, and Drug Dependence 1393 A. Opioid receptor knockout mice 1393 B. Opioid peptide knockout mice 1394 C. Conclusion 1395 D. Perspectives: towar...

Opioid agonists have a broad range of effects on cells of the immune system, including modulation of the inflammatory response, and opioid and chemokine receptors are co-expressed by many white cells. Hetero-oligomerization of the human DOP opioid and chemokine CXCR2 receptors could be detected following their co-expression by each of co-immunoprecipitation, three different resonance energy tra...

Human mu opioid receptor gene polymorphisms and vulnerability to substance abuse. Sequence variations in the mu-opioid receptor gene (OPRM1) associated with human addiction to heroin. Sequence variability and candidate gene analysis in complex disease: association of mu opioid receptor gene variation with substance dependence. Mu opioid receptor gene variants: lack of association with alcohol d...