Response variability to ischémie injury in the Mongolian gerbil: An electroencephalographic and behavioral study

The early effects of 5 or 10 min global cerebral ischemia, sham operation and halothane anesthesia were evaluated in Mongolian gerbils by means of electroencephalography (EEC), neurological examination and passive avoidance training. The "ischemia-sensitive" gerbils (33% and 64% of the 5 and 10 min ischémie groups, respectively) died during carotid ligation or within 24 h; the "ischemia-resistant" gerbils showed variable behavioral responses. Six hours after ischemia, all of the animals presented EEC activity characterized by increased delta (1-4 Hz) activity and a decreased theta2 (6-9 Hz) band, with a tendency to recovery at 24 h. Learning impairment was observed in 5 of the 5 min ischémie animals (83%) and in 1 sham (17%) and 1 halothane (17%) control. Fourteen days after ischemia, histologie damage was observed in 4 ischémie gerbils and 1 sham control. On the whole, this study confirms the widely variable susceptibility of gerbils to cerebral ischemia. Moreover, although the variable effects of carotid occlusion have been attributed to multiple factors involving the cerebrovascular system, our data suggest that endogenous cellular mechanisms might protect against ischemia. In view of this consideration, it would be useful to investigate the molecular causes of the variable cerebral ischémie tolerance shown by Mongolian gerbils.