Opioids exogenous

The term opioid refers to any exogenous substance that acts as an agonist at any of several receptors. Opioid antagonists are drugs that bind to a receptor but produce no actions. The poppy plant, Papaver somniferum, from which opium is obtained, is grown in many areas of the world. Morphine constitutes 10% of opium, and codeine can be obtained direcdy from opium. Semisynthetic opioids such as heroin and oxycodone are obtained directly or indirectly from morphine. There are other distinct chemical classes of drugs with opioid actions, including the methadones. 

Although controversial, findings as to how chronically administered morphine modulates neutrophil chemotaxis and function, a growing consensus believes that morphine is suppressive in the recruitment and functional aspects of these cells during an innate immune response. When peripheral human blood neutrophils were pretreated with exogenous opioids, lL-8-induced chemotaxis was inhibited (Grimm et al. 1998). Conversely, Simpkins et al. reported an increase in neutrophil chemotaxis... 

Carpentier PA, Duncan DS, Miller SD (2008) GUal toU-hke receptor signaling in central nervous system infection and autoimmunity. Brain Behav Immun 22 140-147 Carr DJ, Serou M (1995) Exogenous and endogenous opioids as biological response modifiers. Immunopharmacology 31 59-71... 

A. Action of endogenous and exogenous opioids at opioid receptors... 

Narcotic addiction Blockade of the effects of exogenously administered opioids. A/co/ o//s/t . Treatment of alcohol dependence. 

Kromer W. Endogenous and exogenous opioids in the control of gastrointestinal motility and secretion. Pharmacol Rev 1988 40 121-162. 

Klee H, Wright S, Carnwath T Merrill J (2001). The role of substitute therapy in the treatment of problem amphetamine use. Drug and Alcohol Review, 20, 417-29 Klein GW (1997). Treatment comphcations of methadone maintenance the impact of a high dose exogenous opioid on the living skills, learning and cognition of patients. Alcoholism, 33, 55-68... 

As described in Chapter 31, opioids comprise a large family of endogenous and exogenous agonists at three G protein-coupled receptors the N-, K-, and 5-opioid receptors. Although all three receptors couple to inhibitory G proteins (ie, they all inhibit adenylyl cyclase), they have distinct. 

Possible Supraspinal Sites of Action and Interaction with Endogenous and Exogenous Opioids... 

Naltrexone is an orally available opioid receptor antagonist that blocks the effects of exogenous... 

Animal and human clinical studies demonstrate that both endogenous and exogenous opioids can also produce opioid-mediated analgesia at sites outside the CNS. Pain associated with inflammation seems especially sensitive to these peripheral opioid actions. The identification of functional p receptors on the peripheral terminals of sensory neurons supports this hypothesis. Furthermore, activation of peripheral preceptors results in a decrease in sensory neuron activity and transmitter release. Peripheral administration of opioids, eg, into the knees of patients undergoing arthroscopic knee surgery, has shown some clinical benefit. If they can be developed, opioids selective for a peripheral site would be useful adjuncts in the treatment of inflammatory pain (see Ion Channels Novel Analgesics). Moreover, new peripherally acting dynorphins may provide a novel means to treat visceral pain. 

Endogenous opioids and exogenously administered delta opioid receptor agonists have been demonstrated to have antidepressant-like effects in animal models used to evaluate novel antidepressant compounds. This chapter reviews some of the previous research investigating the role of the opioid system, and more specifically the delta opioid receptor system, in clinical depression and in animal models used to study human depression and antidepressant treatments. In addition, this chapter discusses the interpretation of animal models of depression and their uses in the evaluation of new potential therapeutics. 

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