Astrocytic Cx 43 and Cx 40 in the mouse hippocampus during and after pilocarpine-induced status epilepticus.

Astrocytes have now been well accepted to play important roles in epileptogenesis by controlling gliotransmitter release and neuronal excitability, contributing to blood-brain barrier dysfunction and involving in brain inflammation. Recent studies indicate that abnormal expression of gap junction protein connexin (Cx) may also be a contributing factor for seizure generation. To further address this issue, we investigated the progressive changes of Cx 43 and Cx 40 in the mouse hippocampus at 4 h, 1 day, 1 week and 2 months during and after pilocarpine-induced status epilepticus (PISE). The co-localization of Cx 43 and Cx 40 with glial fibrillary acidic protein (GFAP) was also examined. We observed that Cx 43 and Cx 40 protein expression remained unaltered at 4 h during and at 1 day (acute stage) after PISE. However, their expression was significantly increased in CA1 and CA3 areas and in the dentate gyrus at 1 week (latent stage) and 2 months (chronic stage) after PISE. Double immunofluorescence labeling indicated the localization of Cx 43 and Cx 40 in astrocytes. Combined with progressive neuronal loss in the mouse hippocampus, our results suggest that the increase in gap junctions in the neuronoglial syncytium of reactive astrocytes may be implicated in synchronization of hippocampal hyperactivity leading to neuronal loss and epileptogenesis.