OPIOID-PEPTIDES IN INVERTEBRATES - LOCALIZATION, DISTRIBUTION AND POSSIBLE FUNCTIONAL ROLES

In this review the opioids that have been found in the invertebrates a re discussed. Major emphasis is placed on the arthropods, molluscs and annelids. The article deals largely with the identification and funct ional roles of these peptides. These endogenous opioids are involved i n a wide variety of physiological processes, often serving as neurotra nsmitter substances. Among the putative roles of opioids in invertebra tes are mediation of the release of neurohormones, initiation of prope r behavioural responses, control of thermoregulatory activities and me diation of immune responses. This review concludes with a section that suggests areas of future investigation, along with possible practical applications of these compounds.