RESPONSE VARIABILITY TO ISCHEMIC-INJURY IN THE MONGOLIAN GERBIL - AN ELECTROENCEPHALOGRAPHIC AND BEHAVIORAL-STUDY

The early effects of 5 or 10 min global cerebral ischemia, sham operat ion and halothane anesthesia were evaluated in Mongolian gerbils by me ans of electroencephalography (EEG), neurological examination and pass ive avoidance training. The ''ischemia-sensitive'' gerbils (33% and 64 % of the 5 and 10 min ischemic groups, respectively) died during carot id ligation or within 24 h; the ''ischemia-resistant'' gerbils showed variable behavioral responses. Six hours after ischemia, all of the an imals presented EEG activity characterized by increased delta (1-4 Hz) activity and a decreased theta(2) (6-9 Hz) band, with a tendency to r ecovery at 24 h. Learning impairment was observed in 5 of the 5 min is chemic animals (83%) and in I sham (17%) and I halothane (17%) control . Fourteen days after ischemia, histologic damage was observed in 4 is chemic gerbils and I sham control. On the whole, this study confirms t he widely variable susceptibility of gerbils to cerebral ischemia. Mor eover, although the variable effects of carotid occlusion have been at tributed to multiple factors involving the cerebrovascular system, our data suggest that endogenous cellular mechanisms might protect agains t ischemia. In view of this consideration, it would be useful to inves tigate the molecular causes of the variable cerebral ischemic toleranc e shown by Mongolian gerbils.