In contrast to endogenous opioids, the highly addictive drug morphine activates the mu-opioid receptor without causing its rapid endocytosis. It has recently been reported that coapplication of low concentrations of [d-Ala(2),N-Me-Phe(4),Gly(5)-ol]-enkephalin (DAMGO) facilitates the ability of morphine to stimulate mu-opioid receptor endocytosis and prevents the development of morphine toleranc...

Opioids modulate brain dopaminergic function in various experimental paradigms. This study used the rotational model of behavior in rats with unilateral 6-hydroxydopamine-induced lesions of the nigrostriatal pathway to investigate this interaction. Doses of two presynaptically acting dopaminergic drugs, amphetamine and cocaine, were coadministered with several doses of the mu opioid agonist, mo...

Opiates are indispensable for the treatment of moderate to severe pain. The gastrointestinal tract is one of the major victims of the undesired effects of opiates, because the enteric nervous system expresses all major subtypes of opioid receptors. As a result, propulsive motility and secretory processes in the gut are inhibited by opioid analgesics, and the ensuing constipation is one of the m...

The opioid system consists of three receptors, mu, delta, and kappa, which are activated by endogenous opioid peptides processed from three protein precursors, proopiomelanocortin, proenkephalin, and prodynorphin. Opioid receptors are recruited in response to natural rewarding stimuli and drugs of abuse, and both endogenous opioids and their receptors are modified as addiction develops. Mechani...

BackgroundSince the relief of pain in patients with acute myocardial infarction (AMI) is very important; we sought to assess the effect of Entonox as an analgesic drug in our subjects. Our goal was to compare the analgesic effect of Entonox with opioid drugs such as morphine and meperidine. MethodsThis study was a randomized clinical trial, which included 120 patients with wellestablished AMI a...

Purpose: Patients treated with opioid drugs for cancer pain experience different relief responses, raising the possibility that genetic factors play a role in opioid therapy outcome. In this study, we tested the hypothesis that genetic variations may control individual response to opioid drugs in cancer patients. Experimental Design:We tested 1million single-nucleotide polymorphisms (SNP) in Eu...

Opioid drugs have powerful antidiarrheal effects and many patients taking these drugs for chronic pain relief experience chronic constipation that can progress to opioid-induced bowel dysfunction. Three classes of opioid receptors are expressed by enteric neurons: μ-, δ-, and κ-opioid receptors (MOR, DOR, and KOR). MOR and DOR couple to inhibition of adenylate cylase and nerve terminal Ca(2+) c...

Overview Prescription drug abuse, misuse and overdoses are on the rise. In 2010, drug overdoses killed 38,329 Americans, 16,651 of whom died from prescription opioid painkillers such as oxycodone, hydrocodone and methadone. These drugs also were responsible for 420,040 emergency room visits in 2011. Opioid painkiller deaths have increased in lockstep with prescription opioid prescribing, and th...

Purpose: Patients treated with opioid drugs for cancer pain experience different relief responses, raising the possibility that genetic factors play a role in opioid therapy outcome. In this study, we tested the hypothesis that genetic variations may control individual response to opioid drugs in cancer patients. Experimental Design:We tested 1million single-nucleotide polymorphisms (SNP) in Eu...