NITROUS-OXIDE ATTENUATES THE PROTECTIVE EFFECT OF ISOFLURANE ON MICROTUBULE-ASSOCIATED PROTEIN2 DEGRADATION DURING FOREBRAIN ISCHEMIA IN THE RAT

Recently, attention has been focused on the degradation of cytoskeleta l proteins in animal models of cerebral ischemia, as the collapse of c ytoskeletal proteins may be closely related to cytoskeletal disintegra tion and ultimate neuronal cell death. Among these proteins, microtubu le-associated protein a (MAP2) has been shown to be highly vulnerable to ischemic injuries. To determine the degree of anesthetic effect on the collapse of cytoskeletal proteins, we compared the effect of three inhalation anesthetics; isoflurane, halothane, and nitrous oxide (N2O ), on MAP2 degradation during 20 min of forebrain ischemia in the rat. Under equipotent anesthesia, forebrain ischemia was induced by the oc clusion of the bilateral common carotid artery (CCA) combined with a l owering of mean arterial pressure (mAP) to 50 mmHg. After 20 min of is chemia, three regions of the brain, the frontoparietal cortex, brainst em, and hippocampus, were removed and separately homogenized. Subseque ntly, MAP2 of each region was measured using an enzyme-linked immunoso rbent assay (ELISA). In the frontoparietal cortex and hippocampus, MAP 2 was significantly protected from degradation when isoflurane was use d combined with nitrogen (N-2). However, the protective effects of iso flurane were drastically reduced when N2O was given instead of N,. The se results suggest that the use of N2O should be discontinued when sev ere cerebral ischemia is accidentally incurred during anesthetic manag ement. (C) 1997 Elsevier Science Inc.