Dexamethasone inhibits ischemia-induced transient reduction of neurotrophin-3 mRNA in rat hippocampal neurons

DEXAMETHASONE (DEX) increases the expression of neurotrophin-3 (NT-3) in no rmal rat hippocampal neurons, whereas transient forebrain ischemia reduces the NT-3 mRNA level. The effect of DEX on the expression of NT-3 mRNA in in jured brain cells after ischemia has not been investigated, however. Using in situ hybridization and ribonuclease protection assay methods, we studied NT-3 mRNA expression in rats with and without DEX administration after tra nsient forebrain ischemia. Without DEX treatment, NT-3 mRNA was down-regula ted in the hippocampal neurons at 2, 4, 12 h and returned to basal levels 2 4 h following ischemia. With DEX treatment, however, NT-3 mRNA showed no ch ange at 2, 4 and 12 h and increased 24 h after ischemia. The results indica te that DEX inhibits ischemia-induced NT-3 mRNA down-regulation during the first 12 h and up-regulates NT-3 mRNA 24 h after ischemia. DEX administrati on might be effective in influencing some of the pathophysiological effects of ischemia in the hippocampus. (C) 1998 Lippincott Williams & Wilkins.