MICROTUBULE-ASSOCIATED PROTEIN-2 AS AN EARLY INDICATOR OF ISCHEMIA-INDUCED NEURODEGENERATION IN THE GERBIL FOREBRAIN

Microtubule-associated protein 2 (MAP-2) was studied in the gerbil hip pocampus and striatum after transient ischemia. Western immunoblot ana lysis shows that there is a significant decrease of MAP-2 in the dorso lateral sector of the striatum and a slight decrease of MAP-2 in the C A1 region of the hippocampus 6-12 h after ischemia in the gerbil foreb rain. The immunohistochemical staining pattern of MAP-2 in these two r egions also shows a loss of immunostaining of MAP-2. In particular, a beaded MAP-2 immunostaining pattern at the apical dendritic region of the CAI neurons of the hippocampus was found within 12 h after ischemi a compared with the smooth dendritic immunostaining of MAP-2 in normal CA1 neurons. In vitro assays of MAP-2 degradation suggest that dendri tic loss of immunoreactivity after ischemia seen on western blots may be due to calpain I degradation of MAP-2. Loss of MAP-2 in both the st riatum and hippocampus was found to occur earlier than spectrin degrad ation by western blot analysis. These results suggest that loss of MAP -2 may participate in the initial phase of neuronal dysfunction and th at dendritic breakdown may be a first sign of neurodegeneration.