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Opiate Receptors (opiate + receptor)
Selected AbstractsOpioids and opiates: analgesia with cardiovascular, haemodynamic and immune implications in critical illnessJOURNAL OF INTERNAL MEDICINE, Issue 2 2006P. E. MOLINA Abstract. Traumatic injury, surgical interventions and sepsis are amongst some of the clinical conditions that result in marked activation of neuroendocrine and opiate responses aimed at restoring haemodynamic and metabolic homeostasis. The central activation of the neuroendocrine and opiate systems, known collectively as the stress response, is elicited by diverse physical stressor conditions, including ischaemia, glucopenia and inflammation. The role of the hypothalamic,pituitary,adrenal axis and sympathetic nervous system in counterregulation of haemodynamic and metabolic alterations has been studied extensively. However, that of the endogenous opiates/opioid system is still unclear. In addition to activation of the opiate receptor through the endogenous release of opioids, pharmacotherapy with opiate receptor agonists is frequently used for sedation and analgesia of injured, septic and critically ill patients. How this affects the haemodynamic, cardiovascular, metabolic and immune responses is poorly understood. The variety of opiate receptor types, their specificity and ubiquitous location both in the central nervous system and in the periphery adds additional complicating factors to the clear understanding of their contribution to the stress response to the various physical perturbations. This review aims at discussing scientific evidence gathered from preclinical studies on the role of endogenous opioids as well as those administered as pharmacological agents on the host cardiovascular, neuroendocrine, metabolic and immune response mechanisms critical for survival from injury in perspective with clinical observations that provide parallel assessment of relevant outcome measures. When possible, the clinical relevance and corresponding scenarios where this evidence can be integrated into our understanding of the clinical implications of opiate effects will be examined. Overall, the scientific basis to enhance clinical judgment and expectations when using opioid sedation and analgesia in the management of the injured, septic or postsurgical patient will be discussed. [source] Clinical issues in using buprenorphine in the treatment of opiate dependenceDRUG AND ALCOHOL REVIEW, Issue 3 2000Dr A. Chadderton MB Abstract This paper looks at the current role of buprenorphine in the treatment of opiate dependence. It suggests that buprenorphine is a useful alternative to methadone and that in at least some cases it may be the preferred option. Buprenorphineis a partial agonist and a partial antagonist with a ceiling of opiate activity probably approximately equal to 30mg methadone. It achieves this at a dose of 10-12mg, although there is considerable individual variation. Because of its ceiling effect it has a good safety profile compared to full agonists such as methadone although some overdose deaths, particularly in conjunction with benzodiazepine abuse, have been reported in France. Induction of buprenorphine may take slightly longer than for methadone and there is a higher dropout rate compared to methadone in the first 2 weeks. This is probably due to the antagonist action of buprenorphine causing more withdrawal symptoms in comparison to methadone. Also, the ceiling effect for buprenorphine means that some clients do not experience sufficient opiate activity to satisfy them. Buprenorphine has a long half-life and dissociates slowly from opiate receptors. Most clients can be dosed second-daily but some find this unacceptable due to mood swings and/or withdrawal symptomson the second day. For these clients daily dosing is required. Transferring from buprenorphine to methadone is straightforward and well tolerated by clients. Transferring from methadone to buprenorphine, however, is more difficult because of the partial antagonist action of buprenorphine. Clients experience withdrawal symptoms that can take up to 2 weeks to settle. Most clients find these symptoms unacceptable when transferring from doses of over 30mg of methadone. The optimum method for transferring from methadone to buprenorphine is still to be determined. Withdrawal from buprenorphine appears to be relatively easier than from methadone. This is presumably due to buprenorphine's partial agonist effect at mureceptors. It is expected that during 2000 buprenorphine will be approved for use in Australia for the treatment of opiate dependence. It may well becomea first-line choice for opiate replacement in heroin dependence. It is also likely to be useful in assisting detoxification fromboth methadone and heroin. [source] A test of the opponent-process theory of motivation using lesions that selectively block morphine rewardEUROPEAN JOURNAL OF NEUROSCIENCE, Issue 12 2007Hector Vargas-Perez Abstract The opponent-process theory of motivation postulates that motivational stimuli activate a rewarding process that is followed by an opposed aversive process in a homeostatic control mechanism. Thus, an acute injection of morphine in nondependent animals should evoke an acute rewarding response, followed by a later aversive response. Indeed, the tegmental pedunculopontine nucleus (TPP) mediates the rewarding effects of opiates in previously morphine-naive animals, but not other unconditioned effects of opiates, or learning ability. The aversive opponent process for acute morphine reward was revealed using a place-conditioning paradigm. The conditioned place aversion induced by 16-h spontaneous morphine withdrawal from an acute morphine injection in nondependent rats was abolished by TPP lesions performed prior to drug experience. However, TPP-lesioned rats did show conditioned aversions for an environment paired with the acute administration of the opioid antagonist naloxone, which blocks endogenous opioids. The results show that blocking the rewarding effects of morphine with TPP lesions also blocked the opponent aversive effects of acute morphine withdrawal in nondependent animals. Thus, this spontaneous withdrawal aversion (the opponent process) is induced by the acute rewarding effects of morphine and not by other unconditioned effects of morphine, the pharmacological effects of morphine or endogenous opioids being displaced from opiate receptors. [source] Impaired inhibitory G-protein function contributes to increased calcium currents in rats with diabetic neuropathyJOURNAL OF THE PERIPHERAL NERVOUS SYSTEM, Issue 2 2002KE Hall There is a growing body of evidence that sensory neuropathy in diabetes is associated with abnormal calcium signaling in dorsal root ganglion (DRG) neurons. Enhanced influx of calcium via multiple high-threshold calcium currents is present in sensory neurons of several models of diabetes mellitus, including the spontaneously diabetic BioBred/Worchester (BB/W) rat and the chemical streptozotocin (STZ)-induced rat. We believe that abnormal calcium signaling in diabetes has pathologic significance as elevation of calcium influx and cytosolic calcium release has been implicated in other neurodegenerative conditions characterized by neuronal dysfunction and death. Using electrophysiologic and pharmacologic techniques, the present study provides evidence that significant impairment of G-protein-coupled modulation of calcium channel function may underlie the enhanced calcium entry in diabetes. N- and P-type voltage-activated, high-threshold calcium channels in DRGs are coupled to mu opiate receptors via inhibitory G(o)-type G proteins. The responsiveness of this receptor coupled model was tested in dorsal root ganglion (DRG) neurons from spontaneously-diabetic BB/W rats, and streptozotocin-induced (STZ) diabetic rats. Intracellular dialysis with GTPgammaS decreased calcium current amplitude in diabetic BB/W DRG neurons compared with those of age-matched, nondiabetic controls, suggesting that inhibitory G-protein activity was diminished in diabetes, resulting in larger calcium currents. Facilitation of calcium current density (I(DCa)) by large-amplitude depolarizing prepulses (proposed to transiently inactivate G proteins), was significantly less effective in neurons from BB/W and STZ-induced diabetic DRGs. Facilitation was enhanced by intracellular dialysis with GTPgammaS, decreased by pertussis toxin, and abolished by GDPbetaS within 5 min. Direct measurement of GTPase activity using opiate-mediated GTPgamma[(35)S] binding, confirmed that G-protein activity was significantly diminished in STZ-induced diabetic neurons compared with age-matched nondiabetic controls. Diabetes did not alter the level of expression of mu opiate receptors and G-protein alpha subunits. These studies indicate that impaired regulation of calcium channels by G proteins is an important mechanism contributing to enhanced calcium influx in diabetes. [source] Improvement in hepatopulmonary syndrome after methadone withdrawal: A case report with implications for disease mechanismLIVER TRANSPLANTATION, Issue 7 2010Edmund M. T. Lau Spontaneous resolution of hepatopulmonary syndrome (HPS) without liver transplantation or improvement in the underlying liver disease has rarely been reported in the literature. Increased endogenous production of nitric oxide has been implicated in the pathogenesis of HPS. We report the case of a 50-year-old man with hepatitis C cirrhosis who demonstrated dramatic improvement in HPS after withdrawal from chronic methadone therapy. We speculate on the potential role of opiate receptors in the pulmonary vasculature and their effect on nitric oxide signaling as a potential mechanism accounting for the patient's clinical improvement. Liver Transpl 16:870,873, 2010. © 2010 AASLD. [source] Opioids and the gut: pharmacology and current clinical experienceNEUROGASTROENTEROLOGY & MOTILITY, Issue 4 2004H. U. De Schepper Abstract, This article reviews the pharmacology and physiology of opiate receptors and the current and potential uses of opioid agonists and antagonists in clinical gastroenterology. ,-receptors are involved in motor and sensory functions, and their modulation is established for treatment of diarrhea. ,-antagonists have potential to reverse endogenous (e.g., postoperative ileus) or iatrogenic dysmotility (e.g., opioid bowel dysfunction). Modulation of the function of ,-receptors may be a novel approach to control visceral pain in functional gut disorders. Results of formal testing of novel opioid modulators are keenly awaited. [source] Enantiomers of 2-[(Acylamino)ethyl]-1,4-benzodiazepines, Potent ligands of ,-opioid receptor: Chiral chromatographic resolution, configurational assignment, and biological activityCHIRALITY, Issue 9 2001O. Azzolina Abstract Compounds 2a and 3a,e are racemic 2-[(acylamino)ethyl]-1,4-benzodiazepines, tifluadom analogs, with high affinity and selectivity towards the ,-opioid receptor. We describe the enantiomeric separation of all compounds through liquid chromatography with chiral stationary phases, as well as the resolution of the enantiomers of the most interesting compounds, 2a and 3a, by the semipreparative column Chiralpak AD. The configuration of the resolved enantiomers was investigated: the comparative study of CD and 1H NMR spectra shows that compounds (,)- 2a and (,)- 3a have the same absolute configuration of (+)-(S)-tifluadom. A study on the stereoselective interaction with opiate receptors is reported. Chirality 13:606,612, 2001. © 2001 Wiley-Liss, Inc. 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