Opioid system physiological functions

The part played by endogenous opioid systems in the regulation of these various physiological and behavioral functions has led to the experimental application of opiate antagonists in psychiatric disorders. This chapter focuses on autism and self-injury, which are two potential indications for opiate antagonists in pediatric populations. In adults, treatment with opiate antagonists has shown to be useful in the relapse prevention of alcoholism as part of a comprehensive treatment approach (Anton et ah, 1999, 2001). 

Marked changes in physiological functions can occur if naloxone is given when the endorphin system has been modified by opioids. Following the use of naloxone, a reduced plasma prolactin concentration was noted (737). 

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... 

Similar to opioids, the cannabinoid system appears to be intricately involved in normal physiology, specifically in the control of movement, formation of memories, and appetite control. Basic research has discovered that members of this family of compounds have the capacity to protect threatened neurons, thereby slowing neurodegenerative processes that ultimately lead to physical disability. As the function of the physiological role of endocannabinoids becomes clearer, it appears the system may be involved in the pathology of several neurological diseases, specifically multiple sclerosis, spasticity, and pain. In 1999 the German journal, Forschende Komplementar-medizin und Klassische Naturheilkunde (Research in Complementary and Classical Natural Medicine) commented ... 

The idea that interactions between mu and delta contribute to behavioral and physiological effects of opioid agonists has been considered for over a decade. Evidence for mu/delta cooperativity has been obtained using molecular, cellular, and behavioral approaches [46-52]. However, models of mu/delta interaction have not yet been considered in detail from a circuit perspective. Thus, given that both mu and delta agonists can produce antinociception following focal application within the RVM, the question arises whether mu and delta actions in this system are coordinated or functionally independent. This issue has been addressed from two perspectives. 

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