[Neurochemical characteristics of opioid peptides]

Opioid peptides seem to be involved in an increasing number of cerebral functions. It appears from the most recent studies that these peptides are divided into three families: pro-opio-melanocortin, pro-enkephalin and prodynorphin. Unlike conventional neurotransmitters, these substances are fraught with extremely complex problems of specific biosynthesis and degradation. Finally, the multiplicity of opiate receptors and the search for specific endogenous or synthetic ligands raise major fundamental questions concerning the clinical relevance of studies performed on opioid peptides.