Gene/Protein Disease Symptom Drug Enzyme Compound
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Query: UMLS:C0278080 (physical dependence)
 1,658 document(s) hit in 31,850,051 MEDLINE articles (0.00 seconds)

Mu opioid receptor (MOR) agonists such as morphine are extremely effective treatments for acute pain. In the setting of chronic pain, however, their long-term utility is limited by the development of tolerance and physical dependence. Drug companies have tried to overcome these problems by simply "dialing up" signal transduction at the receptor, designing more potent and efficacious agonists and more long-lasting formulations. Neither of these strategies has proven to be successful, however, because the net amount of signal transduction, particularly over extended periods of drug use, is a product of much more than the pharmacokinetic properties of potency, efficacy, half-life, and bioavailability, the mainstays of traditional pharmaceutical screening. Both the quantity and quality of signal transduction are influenced by many regulated processes, including receptor desensitization, trafficking, and oligomerization. Importantly, the efficiency with which an agonist first stimulates signal transduction is not necessarily related to the efficiency with which it stimulates these other processes. Here we describe recent findings that suggest MOR agonists with diminished propensity to cause tolerance and dependence can be identified by screening drugs for the ability to induce MOR desensitization, endocytosis, and recycling. We also discuss preliminary evidence that heteromers of the delta opioid receptor and the MOR are pronociceptive, and that drugs that spare such heteromers may also induce reduced tolerance.
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PMID:How to design an opioid drug that causes reduced tolerance and dependence. 2043 53

Opioids continue to play a major role in medicine, but not without problems. Side effects limit their utility medically, while the potential of addiction has had a major societal impact. Pharmacologists have been trying to develop opioids lacking side effects since the first derivative, heroin, was synthesized in the 1870s. The identification of opioid receptors about 40 years ago opened up new insights into our understanding of opioid action, fueled by the molecular biology revolution of the 1980s and 1990s. A major result of these studies was the discovery that the mu opioid receptor gene, Oprm1, undergoes extensive alternative splicing in mice, rats, and humans. This single gene generates three sets of proteins, each containing many variants. The object of this review is to describe these variants and how they can be targeted to generate safer, effective analgesic drugs. Mu opioid receptor multiplicity was first suggested over 35 years ago based upon a series of selective antagonists and detailed binding assays. The identification of the different classes of mu opioid receptor splice variants enabled us to target one of the classes of splice variants to obtain potent analgesics lacking respiratory depression, physical dependence, and reward behavior. They also displayed no cross tolerance to morphine analgesia and had diminished effects on gastrointestinal transit. Forty years after the identification of opioid-binding sites in brain the promised land of safer, nonaddictive analgesics is in sight.
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PMID:Mu Opioid Pharmacology: 40 Years to the Promised Land. 2941 24

Mu opioid receptor agonists are among the most powerful analgesic medications but also among the most addictive. The current opioid crisis has energized a quest to develop opioid analgesics that are devoid of untoward effects. Since their discovery in the 1970's, there have been major advances in our understanding of the endogenous opioid systems that these drugs target. Yet many questions remain and the development of non-addictive opioid analgesics has not been achieved. However, access to new molecular, genetic and computational tools have begun to elucidate the structural dynamics of opioid receptors, the scaffolding that links them to intracellular signaling cascades, their cellular trafficking and the distinct ways that various opioid drugs modify them. This mini-review highlights some of the chemical and pharmacological findings and new perspectives that have arisen from studies using these tools. They reveal multiple layers of complexity of opioid receptor function, including a spatiotemporal specificity in opioid receptor-induced cellular signaling, ligand-directed biased signaling, allosteric modulation of ligand interactions, heterodimerization of different opioid receptors, and the existence of slice variants with different ligand specificity. By untangling these layers, basic research into the chemistry and pharmacology of opioid receptors is guiding the way towards deciphering the mysteries of tolerance and physical dependence that have plagued the field and is providing a platform for the development of more effective and safer opioids.
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PMID:Untangling the complexity of opioid receptor function. 3025 Mar 8