Microglial displacement of GABAergic synapses has endogenous protective function in generation of complex febrile seizures

OBJECTIVE Microglia-mediated dis-placement of synapses has been reported in the setting of experimental neuroinflammation,but its role in neurological disorders is poorly understood.Complex febrile seizures(FS) are the most common infantile seizures,yet its pathological progress is largely unknown.METHODS Mice pups(postnatal 8-10 d) were posted to 43℃ hyperthermia condition to develop FS,and then the latency and threshold of seizures were determined.The displacement of synapses was observed through immunofluorescence staining.We researched whether microglial displacement of GABAergic synapses will influence complex FS-induced increase in GABAergic neurotransmission and neuronal excitability with patch-clamp electrophysiology.Moreover,we used the CD11 bD TR mice to selective ablation of microglia or pharmacological inhibition of microglia to observe their effects on susceptibility to FS and synaptic stripping.RESULTS GABAergic presynaptic terminals surrounding neuronal soma and GABAergic transmissions were increased in complex FS.Meanwhile,the activated microglia ensheathe glutamatergic neuronal soma to displace,but do not phagocytize,GABAergic presynaptic terminals.Patch-clamp electrophysiology established that the microglial displacement of GABAergic synapses reduced complex FS-induced increase in GABAergic neurotransmission and neuronal excitability,while GABA exerts excitatory action in this immature stage.Moreover,pharmacological inhibition of microglial displacement of GABAergic synapses or selective ablation of microglia in CD11 bDTR mice promoted the generation of complex FS.CONCLUSION Displacement of GABAergic synapses by microglia is a protective event in the pathological progress of complex FS.

Subicular pyramidal neurons gate drug resistance in temporal lobe epilepsy

OBJECTIVE To understand the underlying mechanisms of drug resistant temporal lobe epilepsy(TLE).METHODS In vivo and vitro electrophysiology,optogenetics and chemogenetics were used in a classic multi-drug resistant TLE model.RESULTS Subicular pyramidal neuron activity was not inhibited by the anti-epileptic drug phenytoin in drug resistant rats.This phenomenon was specific to the subiculum,but did not involve surrounding temporal lobe regions.Selective inhibition of subicular pyramidal neurons by both optogenetics and chemogenetics reversed drug resistance.In contrast,selective activation of subicular pyramidal neurons directly induced drug resistance in drug responsive rats.Furthermore,long-term low frequency stimulation at the subiculum,which is clinically feasible,inhibited the activity of subicular pyramidal neurons and reversed drug resistance.CONCLUSION Subicular pyramidal neurons might be a key ″ switch″ mediating drug resistance in TLE and represent a new potential target for more precise treatment of drug resistant TLE.

Modulation of abnormal neuronal circuit in temporal lobe epilepsy

OBJECTIVE Temporal lobe epilepsy(TLE)is one of the most common types of human epilepsy,and they are often resistant to current treatments.METHODS By using optogenetic,electrophysiological,imaging and pharmacology strategies,we aimed toinvestigate the underlying circuit mechanism of TLE and tried to developthe novel and efficient approach to control epilepsy.RESULTS(1)Using micro PET and multichannel EEG recording,we found an abnormal neural network,characterized by early hypometabolism and after discharge spread,during the epileptogenensis of TLE.(2)Deep brain stimulation,especially low frequency stimulation,targeted the epileptic focus and the areas outside of the focus(critical regions for seizure spread),such as the piriform cortex,cerebellum,entorhinal cortex or subiculum,reduced seizure severity in TLE.Its anti-epileptic effect is time-window dependent and polarity dependent,which shows a promising strategy for treating epileptic seizures.(3)Using an optogenetic strategy,we demonstrated that excitatory projection from entorhinal cortex to hippocampus instructs the brain-stimulation treatments of epilepsy.(4)Our data from both the clinical and experimental studies further demonstrated that a disinhibitory GABAergic neuronmediated microcircuit in the subiculum contributes to secondary generalized seizures in TLE.(5)Finally,based on abnormal synchronization of the electrical activity in epileptic circuit,we developed electroresponsive hydrogel nanoparticles modified with angiopep-2 to facilitate the delivery of the antiepileptic drug phenytoin sodium,which greatly improves the therapeutic index.CONCLUSION Our findings may update the current view of epileptic neuronal networks and suggest possible promising ways for epilepsy treatment.