Effects of minocycline on dendrites, dendritic spines, and microglia in immature mouse brains after kainic acid‐induced status epilepticus

Abstract Purpose This study aimed to investigate whether minocycline could influence alterations of microglial subtypes, the morphology of dendrites and dendritic spines, the microstructures of synapses and synaptic proteins, or even cognition outcomes in immature male mice following status epilepticus (SE) induced by kainic acid. Methods Golgi staining was performed to visualize the dendrites and dendritic spines of neurons of the hippocampus. The microstructures of synapses and synaptic proteins were observed using transmission electron microscopy and western blotting analysis, respectively. Microglial reactivation and their markers were evaluated using flow cytometry. The Morris water maze (MWM) test was used to analyze spatial learning and memory ability. Results Significant partial spines increase (predominate in thin spines) was observed in the dendrites of neurons after acute SE and partial loss (mainly in thin spines) was presented by days 14 and 28 post‐SE. The postsynaptic ultrastructure was impaired on the 7th and 14th days after SE. The proportion of M1 microglia increased significantly only after acute SE Similarly, the proportion of M2 microglia increased in the acute stage with high expression levels of all surface markers. In contrast, a decrease in M2 microglia and their markers was noted by day 14 post‐SE. Minocycline could reverse the changes in dendrites and synaptic proteins caused by SE, and increase the levels of synaptic proteins. Meanwhile, minocycline could inhibit the reactivation of M1 microglia and the expression of their markers, except for promoting CD200R. In addition, treatment with minocycline could regulate the expression of M2 microglia and their surface markers, as well as ameliorating the impaired spatial learning and memory on the 28th day after SE. Conclusions Dendritic spines and microglia are dynamically changed after SE. Minocycline could ameliorate the impaired cognition in the kainic acid‐induced mouse model by decreasing the damage to dendrites and altering microglial reactivation.