Parvalbumin Neurons In The Anterior Nucleus Of Thalamus Control Absence Seizures

Objective: Absence seizure is a type of generalized seizure characterized by sudden transient loss of consciousness accompanied by behavioral arrest,and symmetrical 3Hz spike wave discharges(SWDs)on the EEG during the seizure.Therefore,it is urgent to find effective therapeutic methods.The anterior nucleus of the thalamus(ANT)is located in the anterior part of the thalamus and serves as a relay nucleus that connects the cortex and subcortical structures.It has been widely accepted as an effective target for deep brain stimulation in the treatment of refractory epilepsy.Functional magnetic resonance imaging suggests there is an increase volume in ANT.Previous studies have suggested that absence seizures are related to the dysfunction of Gamma aminobutyric acid(GABA)in the thalamus,parvalbumin(PV)neurons are a subset of GABAergic inhibitory interneurons that mediate feed-forward inhibition within the cortico-thalamocortical network of the brain.Therefore,in this study,we used chemogenetic methods to explore the mechanism of specific regulation of ANT PV neurons on absence seizures.Methods: 1.Establish the model of absence seizures.Wild-type mice were randomly divided into three groups,with each group(n=6)receiving pentylenetetrazole(PTZ)at concentrations of 30mg/kg,35mg/kg,and 40mg/kg.The electroencephalogram of mice was recorded and the behavior of mice were observed.2.To observe the effect of chemogenetics specific activation of ANT PV neurons on PTZ induced absence seizures.Chemogenetics was used to specifically activate PV neurons in ANT,we record and statistically analyze the total number of SWDs,the total duration of SWDs,and the latent period of SWDs after one hour of PTZ administration in control group(n=8)and experimental group mice(n=8).Then we analyze the changes of EEG rhythm before and after the seizure,and observe the behavioral changes of mice.3.To observe the effect of chemogenetics specific inhibition of ANT PV neurons on PTZ induced absence seizures.Chemogenetics was used to specifically inhibit PV neurons in ANT,we record and statistically analyze the total number of SWDs,the total duration of SWDs,and the latent period of SWDs after one hour of PTZ administration in control group(n=8)and experimental group mic(n=8).Then we analyze the changes of EEG rhythm before and after the seizure,and observe the behavioral changes of mice.4.To observe whether chemogenetics specific inhibition of PV neurons in ANT can directly induce absence seizures.Chemogenetics was used to specifically inhibit ANT PV neurons.We record and statistically analyze the frequency and total duration of SWDs within 1 hour after intraperitoneal injection of CNO(1mg/kg),and we analyze the changes of EEG rhythm before and after the seizure,and observe the behavioral changes of mice,then we compared with the control group.Results: 1.Different doses of PTZ induces different types of seizure.Low dose intraperitoneal injection of PTZ(30mg/kg)in mice can 100% induce bilateral synchronous SWDs.We found that all mice displayed behavioral arrest and beard shaking,and neck muscle shaking.Intermediate concentrations of PTZ(35mg/kg)tend to induce tonic-clonic seizures,the incidence of seizures was approximately 83.3%.While high doses of PTZ(40mg/kg)can all evoked tonicclonic seizures(100%).Therefore,30mg/kg PTZ can be used as the optimal concentration to induced absence seizures.2.Chemogenetic activation of ANT PV neurons can aggravate PTZ-induced absence seizures.Compared with control group,the experimental group showed a significant increase in the number of SWDs(P<0.005),the total duration of SWDs(P<0.001),and a significant shorten in the latency of SWDs(P<0.05).There was a significant difference in two group.Moreover,by analyzing the alpha,beta,theta,delta,gamma rhythms in ictal states compared with baseline conditions,it was found that compared with the control group,the experimental group significantly promoted the increase of delta rhythms(P <0.05),which was statistically significant.3.Chemogenetic inhibition of ANT PV neurons can also aggravate PTZ-induced absence seizures.Compared with the control group,the experimental group significantly promoted the number of SWDs(P<0.05),the total duration of SWDs(P<0.01),and a significant shorten in the latency of SWDs(P<0.01).There was a significant difference in two group.Moreover,by analyzing the alpha,beta,theta,delta,gamma rhythms in ictal states compared with baseline conditions,it was found that compared with the control group,Moreover,the spectral analysis showed that delta rhythm was obviously increased(P<0.05)in ictal states compared with baseline conditions in both control group and experimental group.3.Inhibition of ANT PV neurons alone are sufficient to induce generalized SWDs.The experimental group can directly induce absence seizures without PTZ.Compared with the control group which using PTZ to construct the model,the experimental group mice showed similar frequency(P>0.05)and duration of SWDs(P>0.05),there were not significant differences between them.The clinical manifestations of experimental group were similar to the control group.Conclusion: Our findings indicated that either activation or inhibition of ANT PV neurons might disturb the intrinsic delta rhythms in the cortex and promote the generalization of SWDs,which highlighted the importance of maintaining the activity of ANT PV neurons in absence seizures.This study not only provides a theoretical basis for the pathogenesis of absence seizures,but also provides potential targets for its treatment.