mu opioid receptors are targets of native opioid peptides and addictive analgesic drugs. A major clinical liability of opiate drugs is their ability to cause physiological tolerance. Individual opiates, such as morphine and etorphine, differ both in their ability to promote physiological tolerance and in their effects on receptor regulation by endocytosis. Here, we demonstrate that arrestins pl...

Opioid analgesics are the mainstay in the treatment of moderate-to-severe pain, yet their use is frequently associated with adverse effects, the most common and debilitating being constipation. Opioid-induced motor stasis results from blockade of gastrointestinal peristalsis and fluid secretion, and reflects the action of the endogenous opioid system in the gut. Methylnaltrexone and alvimopan a...

Drug overdose death rates have increased steadily in the United States since 1979. In 2008, a total of 36,450 drug overdose deaths (i.e., unintentional, intentional [suicide or homicide], or undetermined intent) were reported, with prescription opioid analgesics (e.g., oxycodone, hydrocodone, and methadone), cocaine, and heroin the drugs most commonly involved . Since the mid-1990s, community-b...

Although methadone (an opioid agonist) and buprenorphine (a partial opioid agonist) have evidence to support their use in treating opioid use disorder, they remain misunderstood and underutilized. In this article, we outline the risks and benefits of using these drugs as maintenance therapy in opioid-dependent patients.

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 and opioid-like receptors are activated by a variety of endogenous peptides including [Met]enkephalin (met), [Leu]enkephalin (leu), β-endorphin (β-end), α-neodynorphin, dynorphin A (dynA), B (dynB), big (Big dyn), nociceptin/orphanin FQ (N/OFQ); endomorphin-1 endomorphin-2 also potential peptides. The Greek letter nomenclature for the opioid receptors, μ, δ κ, is well established, NC-IUP...

Considering the clinical significance of opioids, especially their application for the treatment of severe painful conditions including cancer pain and the requirement for the synthesis of more specific drugs with lower side effects, this study was conducted to perform a preliminary investigation on six newly developed opioid drugs. Our aim was to introduce drugs that act selectively on the opi...

Opioid receptors of the mu-, delta- and kappa-subtypes mediate the potent analgesic and addictive actions of opioid drugs. They also regulate responses to pain, stress and emotions when activated by endogenous opioid peptides. Recently, mice lacking opioid receptors or opioid peptides have been produced by gene targeting, providing molecular tools to study opioid function in vivo. Observations ...