ABSTRACT
OBJECTIVE Epileptic networks are char-acterized as two states,seizures or more prolonged inter-ictal periods.However,cellular mechanisms underlying the contribution of interictal periods to ictal events remain unclear.METHODS Here,we present the procedure for labeling seizure-activated and interictal-activated neuro-nal ensembles in mouse hippocampal kindling model using an enhanced-synaptic-activity-responsive element.This technique is combined with genetically encoded effectors to characterize and manipulate neuronal ensembles recruited by focal seizures(FS-Ens)and interictal periods(IP-Ens)in piriform cortex,a region that plays a key role in seizure generation.RESULTS Ca2+ activities and histo-logical evidence reveal a disjointed correlation between the two ensembles during FS dynamics.Optogenetic acti-vation of FS-Ens promotes further seizure development,while IP-Ens protects against it.Interestingly,both ensem-bles are functionally involved in generalized seizures(GS)due to circuit rearrangement.IP-Ens bidirectionally modulates FS but not GS by controlling coherence with hippocampus.CONCLUSION This study indicates that the interictal state may represent a seizure-preventing environment,and the interictal-activated ensemble may serve as a potential therapeutic target for epilepsy.
ABSTRACT
Epilepsy is a common neurological disorder characterized by hyperexcitability in the brain. Its pathogenesis is classically associated with an imbalance of excitatory and inhibitory neurons. Calretinin (CR) is one of the three major types of calcium-binding proteins present in inhibitory GABAergic neurons. The functions of CR and its role in neural excitability are still unknown. Recent data suggest that CR neurons have diverse neurotransmitters, morphologies, distributions, and functions in different brain regions across various species. Notably, CR neurons in the hippocampus, amygdala, neocortex, and thalamus are extremely susceptible to excitotoxicity in the epileptic brain, but the causal relationship is unknown. In this review, we focus on the heterogeneous functions of CR neurons in different brain regions and their relationship with neural excitability and epilepsy. Importantly, we provide perspectives on future investigations of the role of CR neurons in epilepsy.