Electroretinogram of the Isolated Dog’s Head after Prolonged Complete Brain Ischemia

Abstract

In experiments with 34 isolated dog heads, the electroretinogram (ERG) was registered at the beginning and after the end of complete normothermic brain ischemia lasting for 20, 30, 45 or 60 min. Compared with the EEG, the survival time of the ERG is significantly longer and the latency of recovery significantly shorter. Smaller but also significant differences persist even if the survival and reappearance of typical complex ERG configuration are evaluated. The greater resistance of the ERG against ischemia is explained if one assumes that the ERG is generated by different structures (individual layers of the retina and probably also surrouding nonneural tissues) which are less sensitive to oxygen deprivation than the brain cortex. The excessive values concerning the resistance of the ERG as given in the literature are partly due to the incompleteness of the ischemia and due to the concomitant evaluation of DC potantials.