Chapter 28 Sites of action of opiates in production of analgesia

Publisher Summary This chapter discusses the sites of action of opiates in the production of analgesia. Opiates given systemically alter the response suggesting that the encoding of the physical stimulus has been altered. This effect is mediated by specific classes of receptors as characterized by their pharmacological profile. Opiates may exert a direct effect on the peripheral terminals of primary afferent nociceptors and alter the peripheral sensitivity. A drug exerts an action within the neuraxis on discrete populations of opioid receptors to alter pain behavior. The brains of several species have been mapped using stereotaxically implanted guides for regional sensitivity to the effects of opioid drugs with respect to a variety of pain behaviors. The spinal administration of opioids and the effect on pain behavior have been carried out in a wide variety of species, including mouse, rabbit, cat, sheep and primate, and a powerful analgesia has been routinely reported. The effects of opiates at moderate systemic doses produce changes that are the gold standard of analgesia.