Immunohistochemical Expression of c-fos Protein and Histologic Findings after Instillation of Kainic Acid in Hippocampus of Neonatal Rat Brain

Chae, Soo Ahn; Kim, Yong Soo; Yoo, Byoung Hoon; Lee, Won Bok

Abstract

PURPOSE: c-fos is rapidly and transiently induced in the intact CNS by a wide variety of exogenous stimuli that include seizures, glutamate receptor activation, sensory stimulation and stress. In adult animals, systemic KA administration produces limbic seizures that results in c-fos protein expression, irreversible morphological changes and localized neuronal death. So we studied the pattern of c-fos protein expression and histological findings in hippocampal formation, following kainic acid-induced seizures during the postnatal period in the rat.
METHODS
Sprague-Dawley rat pups ranging from 8 to 10 days of age, received kainic acid(KA, 5mg/kg) by intraperitoneal injection. Control rats were injected with normal saline. The rats were perfused and fixed with 4% buffered paraformaldehyde at varying time-intervals after KA injection, the brains were sectioned and immunohistochemically stained for c-fos protein and performed HE staining.
RESULTS
In the hippocampus, immunohistochemistry showed that c-fos protein expressed at 12 hr after KA injection and disappeared thereafter. c-fos protein expressed in all sectors of the hippocampus but most densely expressed in CA1 and CA3 sectors. Rarely c-fos expression was seen in the granular cell layer of dentate gyrus. There were no histologic changes in the hippocampus at 2 weeks after KA injection.
CONCLUSION
c-fos, a proapoptotic gene in adult rats, seemed to have an additive role in neuronal cell adaptation to exogenous stimuli in neonatal rats. As a result, it suggests that the roles of c-fos in neuronal cells after noxious stimuli are different between neonatal and adult rats.