Abstracts

Rationale: In the present study, we analyzed aquaporin-4 (AQP4) immunoreactivity in the piriform cortex (PC) and the hippocampus of pilocarpine-induced rat epilepsy model to elucidate the roles of AQP4 in brain edema following status epilepticus (SE). Methods: We performed immunohistochemical study for AQP4 and double immunofluorescent staining for AQP4 / glial fibrillary acidic protein (GFAP) in the rat PC and hippocampus of pilocarpine-induced epilepsy model hippocampus. Results: In control animals, AQP4 immunoreactivity was diffusely detected in the PC and the hippocampus. AQP4 immunoreactivity was mainly observed in the end-feet of astrocytes. Twelve hrs - One week after SE, AQP4-deleted area was clearly detected in the PC. In addition, AQP4 immunoreactivity was gradually decreased in the dentate gyrus, not in the CA1-3 regions. These reductions in AQP4 immunoreactivity were correlated to astroglial loss in these regions. Four weeks after SE, AQP4-deleted area was reduced and AQP4 immunoreactivity was enhanced in the PC as compared to controls. Similarly, AQP4 immunoreactivity in the hippocampus was increased as compared to control levels. These enhancements of AQP4 immunoreactivity were dependent to reactive astrogliosis. Conclusions: These findings indicate that reduced AQP4 immunoreactivity may result in regional specific edema formation in the PC and the hippocampus following SE.