Time course and regional expression of C-FOS and HSP70 in hippocampus and piriform cortex following soman-induced seizures.
The time course of induction of the proto-oncogene c-fos and the inducible heat shock hsp70 gene was studied from 5 minutes to 24 hours at both transcriptional (c-fos and hsp70 mRNA) and translational levels (C-FOS and HSP72 proteins) in the rat hippocampus and piriform cortex (Pir) after soman-induced seizures. Induction of c-fos was noticed as early as 5 minutes after seizures onset in all fields of hippocampal formation (CA1, CA3, CA4, and dentate gyrus) and in piriform cortex. The most intense induction was observed in piriform cortex. A sustained activation of c-fos occurred in Pir and in CA1, CA3, and CA4 areas of hippocampus. Nevertheless, histological analysis showed rare affected neurons in CA4, whereas damage was severe in Pir and in CA1 and CA3 hippocampal subfields. Induction of hsp70 mRNA occurred but was delayed in all areas previously exhibiting c-fos expression. Nevertheless HSP72 protein was never expressed in the structures where injury was high (i.e., CA1 and piriform cortex) and mainly occurred in the less damaged structure (i.e., CA4 area of hippocampus). Regional expression of glial fibrillary acidic protein mRNA was also studied in order to exclude an astroglial origin of the c-fos and hsp70 gene inductions. Our results demonstrated that after soman induced-seizures 1) there was no strict correlation between time course or intensity of neuronal c-fos induction and subsequent neuropathology, and 2) the most lesioned areas did not express HSP72 protein in spite of intense mRNA induction, suggesting that transcriptional and translational events for hsp70 gene might vary according to the severity of seizure insult.
Baille-Le Crom
V
V
Centre de Recherches du Service de Santé des Armées, Unité de Neurotoxicologie, La Tronche, France.
Collombet
J M
JM
Burckhart
M F
MF
Foquin
A
A
Pernot-Marino
I
I
Rondouin
G
G
Lallement
G
G
D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D002540:Cerebral Cortex / Q000166:cytology / Q000378:metabolism*; D003292:Convulsants; D018840:HSP70 Heat-Shock Proteins / Q000096:biosynthesis*; D006624:Hippocampus / Q000166:cytology / Q000378:metabolism*; D007091:Image Processing, Computer-Assisted; D007150:Immunohistochemistry; D017403:In Situ Hybridization; D008297:Male; D009474:Neurons / Q000378:metabolism; D016760:Proto-Oncogene Proteins c-fos / Q000096:biosynthesis*; D051381:Rats; D017208:Rats, Wistar; D012640:Seizures / Q000139:chemically induced / Q000378:metabolism*; D012999:Soman
D003292:Convulsants; D018840:HSP70 Heat-Shock Proteins; D016760:Proto-Oncogene Proteins c-fos; D012999:Soman