Chapter 19 Endogenous opioid peptides in the descending control of nociceptive responses of spinal dorsal horn neurons

Abstract

Publisher Summary This chapter discusses the endogenous opioid peptides in the descending control of nociceptive responses of the spinal dorsal horn neurons. The identification of opioid receptors and detection of endogenous ligands of these receptors helped in pain research. The differentiation of several types of opiate receptors and the characterization of a series of opioid peptides illustrates the striking complexity of opioid systems. On the basis of their derivation from three distinct precursor molecules (corresponding to three different genes) three families of endogenous opioid peptides may be distinguished as pro-opiomelanocortin (POMC), pro-enkephalin A (PEA), and pro-enkephalin B (PEB) or pro-dynorphin. Opioid systems play an important role in the engagement of centrifugal networks that inhibit the flow of nociceptive information to the brain. A major problem is to establish the identity, location, and mechanisms of action of the opioid peptides and the opioid receptor types involved. The future resolution of such problems should contribute to the development of opioid-based strategies of pain relief specifically targeted on the systems that play a decisive role in the physiological activation of descending inhibition.