This study addresses the question of whether the
cyclooxygenase inhibitors indomethacin and
diclofenac and the glucocorticosteroid
dexamethasone ameliorate neuronal
necrosis following
cerebral ischemia. In addition, since these drugs inhibit the production of
prostaglandins and depress
phospholipase A2 activity, respectively, the importance of
free fatty acids (FFAs) on the development of ischemic neuronal damage was assessed. Neuronal damage was determined in the rat brain at 1 week following 10 min of forebrain
ischemia. The
cyclooxygenase inhibitors, whether given before or after
ischemia, failed to alter the brain damage incurred. Animals given
dexamethasone were divided into three groups and the
drug was administered at a constant dosage of 2 mg/kg: (a) 2 days, 1 day, and 3 h intraperitoneally before (chronic pretreatment), (
b) 3 h intraperitoneally before (acute pretreatment), and (c) 5 min intravenously and 6 h and 1 day intraperitoneally after (chronic posttreatment) induction of
ischemia. Acute pretreatment did not affect the histopathological outcome. Chronic posttreatment of animals with
dexamethasone ameliorated the damage inflicted on the caudate nucleus, but had no effect on other brain areas investigated. Unexpectedly, the chronic pretreatment aggravated the brain damage and caused
seizures following
ischemia. Histopathological data showed massive neuronal damage in these brains. The accumulation of FFA levels during
ischemia was markedly suppressed, and the decrease in the energy charge was curtailed by chronic pretreatment with
dexamethasone. However, brain
glucose levels in control animals and
lactic acid concentrations following 10 min of
ischemia were significantly higher both in the cerebral cortex and in the hippocampus of
dexamethasone-treated animals. These results suggest that aggravation of neuronal
necrosis by chronic
dexamethasone pretreatment could be ascribed to
lactic acidosis due to
hyperglycemia in combination with an action of
dexamethasone on
glucocorticoid receptors in the brain.