ASTROCYTIC HYPERTROPHYC RESPONSE INDUCED BY EARLY LEAD EXPOSURE MODIFIED AFTER GLUCOCORTICOID TREATMENT.

CAPANI, F. ; LOIDL, C. F. ; CEBRAL, E. ; L¡ÜPEZ-COSTA, J. J. ; SELVIN-TESTA, A.

Orlando

Congreso; Society for Neuroscience Meeting; 2002

Delayed effects induced in hippocampal and cerebral cortex astrocytes after lead exposure (PbE) and their modifications after glucocorticoid treatment were studied in rats at 45, 60, 90 and 120 postnatal days (PN). Study was done to determine changes in astrocytes after PbE [1g% lead acetate in drinking water prior to mating and continued after weaning until 120 PN and glucocorticoid (Gluc) treatment after 60 PN administered via injection 50mg/kg/day in corn oil vehicle, for 3 weeks, monday to friday]. Animals were killed at the next day after the end of treatment, and in the next 7, 14 and 28 days. To study astroglia changes we used immunohistochemistry for gliofibrillar acidic protein (GFAP), vimentin (VIM) combined with transmission electron microscopy. At 60 PN astrocyte hypertrophy was revealed by GFAP and VIM. At the end of Gluc treatment hyperactive behavior changed by depression, and large decrease in the GFAP and VIM expression near control levels, despite the high blood lead-levels, were observed in hippocampus and cortex. At the same time, no neuronal alteration were seen. Also, Gluc administration down-regulated the concentration of GFAP, in control rats. Gluc affects regional reactivity induced by the lead without overt citotoxicity, and modifies the synthesis of GFAP through a mechanism distinct from that operating in injury tissue. Gluc (an important regulator of physiological and behavioral responses) inhibits GFAP expression and reduces astroglial reactivity, may alter neuronal milieu indirectly by affecting astrocytes.