SELECTIVE NEURONAL VULNERABILITY AND SPECIFIC GLIAL REACTIONS IN HIPPOCAMPAL AND NEOCORTICAL ORGANOTYPIC CULTURES SUBMITTED TO ISCHEMIA

Neurons from cerebral neocortex and hippocampus exhibit a striking dif ference in vulnerability to transient global ischemia. In order to stu dy the contribution of neuronal connections and neuron-glia interactio ns to this variation in neuronal vulnerability, we used hippocampal an d neocortical cultures submitted to various periods of histotoxic isch emia. Organotypic cultures were exposed at 37 degrees C for 0, 7, 30 a nd 60 min to a glucose-free NaCN-containing medium. Histological analy sis using thionin staining and MAPS immunostaining showed differences in the temporal profile of neuronal damage in hippocampal and neocorti cal structures, i.e., in decreasing order, CA1 (7 min) > CA3 and neoco rtical layers II, III, V, VI (30 min) > DG and neocortical layer TV (6 0 min). In parallel to the neurodegeneration study, the time course an d the regional pattern of microglial and astroglial changes were also examined using GS-B4 isolectin and GFAP as immunohistochemical markers , respectively. The GS-B4 isolectin staining revealed an early (at 7 m in for the hippocampus) and a specific microglial activation located i n areas undergoing neuronal damage. For both organotypic cultures, ast rogliosis occurred later (after 30 min of stress) with no specific reg ional distribution. Both hippocampal and neocortical cultures submitte d to histotoxic ischemia allowed the replication of many of the cellul ar events observed in response to global ischemia in vivo. These findi ngs support the hypothesis that neuron-neuron connections as well as i nteractions between neurons and glial cells are essential to reproduce in vitro the selective neuronal vulnerability described in vivo. (C) 1998 Academic Press.