OPIATE SIGNALING REGULATES MICROGLIA ACTIVITIES IN THE INVERTEBRATE NERVOUS-SYSTEM

1. Evidence supporting the presence in the invertebrate nervous system of a class of glial cells resembling vertebrate microglia was obtaine d in the freshwater snail Planorbarius corneus, These cells are easily identified by their immunopositivity to anti-pro-opiomelanocortin (PO MC)derived peptide antibodies. 2. Invertebrate microglia, as in verteb rates, exhibit macrophage-like activity in vivo and in cell cul tures. These cells respond to the trauma of ganglionic excision and their or ganotypic culture by leaving their location around neurons and moving to the lesion site from which they migrate in the culture dish.3. In v itro, these microglia undergo conformational changes and show phagocyt ic properties in the presence of bacteria or lipopolysaccharide. The a ctivated cells also express tumor necrosis factor-alpha-like material and an increase in nitric oxide synthase, as shown by immunocytochemis try. 4. The inhibitory effect of morphine on the mobility and phagocyt ic activity of invertebrate micro glia provide additional functional e vidence for a possible role of opiate like compounds in downregulating immunoregulatory processes, as also observed in the circulating immun ocytes. (C) 1997 Elsevier Science Inc.