Opioids pain response

Endogenous opioids and opioid receptors inhibit pain responses 932 CLINICAL PAIN 932... 

Pain response to cold water Opioid analgesic... 

The peptide, melatonin, has been implicated in autism. Excess melatonin is thought to decrease learning, memory, attention, emotionality, motivation and pain responses (reviewed Chamberlain Herman, 1990)—all behaviours that are abnormal in autism. Melatonin, released from the pineal gland, is implicated in controlling serotonin and POMC (proopiomelanocortin) peptides, such as beta-endorphin, and an elevation may contribute to, or cause, the serotonin and opioid abnormalities (Chamberlain Herman, 1990). 

Rowbotham, David J. Endogenous Opioids, Placebo Response, and Pain. The Lancet 357 (June 16, 2001) 1901. 

While the physiological basis of acupuncture is incompletely understood, it is now apparent that the endogenous opioid systems are activated by such techniques. Furthermore, when acupuncture is simulated in animals there is a decrease in the pain response to noxious peripheral stimuli, which can be reversed by naloxone. 

Examples of neuropeptides are endorphins and enkephalins, sometimes called naturally occurring opioid peptides because of their ability to bind to the same receptors as morphine. In this family of neuropeptides, there are at least 10 to 15 substances with purported actions on such diverse physiological systems as pain response, memory and learning, appetite, and temperature regulation. 

Zubieta JK, Heitzeg MM, Smith YR, et al. COMT vall58met genotype affects mu-opioid neurotransmitter responses to a pain stressor. Science 2003 299(5610) 1240-3. 

On theoretical grounds ondansetron (a S-HTj-receptor antagonist) might be expected to decrease the effects of drugs that reduce pain transmission because serotonin (5-HT) is thought to affect pain responses via presynap-tic 5-HTj receptors in the spinal dorsal horn. This has been demonstrated for tramadol, ch is not a pure opioid and also acts by enhancing the effects of serotonin and noradrenaline (norepinephrine). However, ondansetron had no effect on alfentanil or morphine analgesia in healthy subjects. 

Mercadante S, Portenoy RK. Opioid poorly-responsive cancer pain, part 1 clinical considerations. / Pain Symptom Manage 2001 21 144-150. 

Smith HD, Pan C, Breitmeyer JB, Royal MA. Acetaminophen produces clinically meartingful pain response and opioid sparing effed after major orthopedic surgery Pooled data from three randomized, placebo controlled trials. RegAnesth Pain Med2009 PSl 21. 

The endogenous opioids are another family of peptides involved in different physiological processes including pain regulation, respiratory control, stress responses, appetite, thermoregulation, and humoral and cellular immune function (Bodnar RJ., 2008). Opioids act through their receptors, which are also members of the GPCR family, and are expressed in the central and peripheral nervous system as well as on cells of the immune system (Henriksen and Willoch 2008 Hauser... 

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