Changes in astrocytic Kir4.1 channel expression and microglial morphology after pilocarpine-induced status epilepticus in rats

Glial cells (astrocytes and microglia) play important roles in modifying epileptogenesis. Especially, astrocytic Kir4.1 channels regulate neuronal excitability by buffering excessive synaptic K+ ions, preventing convulsive seizures. To clarify the changes in astrocytes and microglia in animal model of temporal lobe epilepsy, we analyzed the changes in Kir4.1 channel expression, number and morphology of astrocytes and microglia in early stage (day 3) after pilocarpine (PILO)-induced status epilepticus (SE). Our results showed that both Kir4.1- and GFAP-immunoreactivity-positive astrocytes were markedly reduced by PILO-induced SE. In contrast, the number of microglia was elevated in most regions examined. More specifically, microglia of amoeboid form increased in most temporal lobe regions, while those of ramified, hypertrophied and rod forms elevated in the hippocampus and amygdala. Finally, seizure sensitivity of animals was already increased at day 3 after PILO-induced SE. Our results suggest that the above changes in the astrocytes and microglia features are involved in elevation of seizure susceptibility after PILO-induced SE.