Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: May 27, 2004
Publication Date: N/A
Technical Abstract: Endogenous enkephalins, such as Met-enkephalin and Leu-enkephalin, are a group of small peptides found within the nervous system. In the central nervous system (CNS), enkephalins are synthesized from proenkephalin. Proenkephalin-and enkephalin-containing neurons are widespread in the CNS. Enkephalins have multiple roles in the regulation of physiological and pathological processes, including the pain processes. Enkephalins display analgesic effects by directly modulating the processing of nociceptive information in the local circuits, inhibiting the release of pain-related neuropeptides such as Substance P and the calcitonin-gene-related peptide in the dorsal horn of the spinal cord and the trigeminal nucleus of the brainstem. In addition, the widespread distribution of enkephalins and their receptors throughout the limbic system and the hypothalamus indicate that the enkephalin system is a major regulatory system in modulating stress and non-stress states. Enkephalins, such as Met-enkephalin, also function as immune modulators which link both the nervous system and the immune system, and their interactions. Experimental studies have shown that enkephalins are an important immunomodulatory signaling molecule to exert regulatory actions concerned with the expression of pre-inflammatory cytokines.