INCREASE OF CATECHOL-O-METHYLTRANSFERASE ACTIVITY IN RAT-BRAIN MICROGLIA AFTER INTRASTRIATAL INFUSION OF FLUOROCITRATE, A GLIAL TOXIN

Striatal catechol-O-methyltransferase (COMT), monoamine oxidase B (MAO -B; an astroglial enzyme), alkaline phosphodiesterase I (PDE; a microg lia/macrophage marker) and tyrosine hydroxylase (TH; catecholaminergic neuron marker) activities were analyzed biochemically 1-3 days after infusion of fluorocitrate, an astrocyte damaging agent. Astrocytes, mi croglia and neurons were stained immunohistochemically with specific a ntibodies (against glial fibrillary acidic protein, OX-42 and TH, resp ectively) and with COMT antiserum. Three days after fluorocitrate infu sion the activity of MAO-B was reduced, whereas COMT and PDE activitie s were increased. The elevation of COMT immunoreactivity co-localized to microglial cells, but not to astrocytes. In conclusion, this is the first report indicating that microglia contains COMT activity which m ay be increased in pathological conditions. (C) 1997 Elsevier Science Ireland Ltd.