INDUCTION OF ASTROGLIAL GENE-EXPRESSION BY EXPERIMENTAL SEIZURES IN THE RAT - SPATIOTEMPORAL PATTERNS OF THE EARLY STAGES

The levels of glial fibrillary acidic protein mRNA were analysed by in situ hybridization during the first 6 h in experimental models of sta tus epilepticus in the rat. Two different models of status epilepticus were studied: one is produced by the administration of pilocarpine to lithium-treated rats and the other by the intracerebroventricular adm inistration of kainate. Results obtained in the present study showed a very rapid (as early as 1.5 h in periventricular zones of hypothalamu s, cerebral cortex, and hippocampal area) up-regulation of GFAP mRNA l evels following the pharmacological induction of seizures. Several oth er areas showed a GFAP activation starting at 3 h such as septum, habe nular nuclei, corpus callosum, and cingulum. The comparison of the res ults obtained in the two models of status epilepticus revealed interes ting differences in some brain areas, such as cerebellum and striatum, which can be related to the specific neurotransmitter receptors and n eurochemical pathways stimulated by the drugs. Interestingly, some bra in areas whose neurons are strongly activated by pilocarpine and kaina te (amygdala and CA3 hippocampal field) and that undergo neuronal dege neration did not show the early GFAP response. An interesting spatial feature was observed in several brain regions examined (striatum, sept um, and hypothalamus): the response first appeared in the periventricu lar zones and then diffused to the rest of the brain area. In general GFAP responses in the periventricular zones were early and intense. (C ) 1996 Wiley-Liss, Inc.