The Roles And Mechanisms Of Anterior Lateral Septal Nucleus In Regulating Anxiety-like Behaviors In Mice

Objective: Anxiety disorder is the most common mental disorder among mental diseases,which causes heavy mental pressure and economic burden to individuals and society.Due to the diverse manifestations and complex pathogenesis of the disorder,the neural mechanism of anxiety needs to be clarified.This study explored the modulatory effects of anxiety-like behaviors by glutamatergic and GABAergic neurons in lateral septum(LS)in mice,and the roles of dopaminergic projection to LS in regulating anxiety-like behaviors.Method: By introducing optogenetic techniques,the recombinant adeno-associated viruses(AAV)containing the photo-activator protein Chr2 or the photo-suppressor protein Np HR were injected into the LS in Vglut2-cre and Vgat-cre transgenic mice by stereotactic injection.The optical fibers were embedded into LS after virus injection.2-3 weeks later,Chr2 or Np HR can be stably expressed in LS neurons.Blue light or yellow light was given through the optic fiber to activate or inhibit neurons in LS.The anxiety-like behaviors of mice were analyzed by open-field,elevated plus maze,food and drink ingestion,novelty-suppressed feeding and sugar preference experiment.The retrogradeand anterograde tracing combined with immunofluorescent labeling were used to identify the neural connections between midbrain dopaminergic neurons and LS.Intracranial administrations were used to observe the effects of dopaminergic receptor agonist and antagonist on anxiety-like behavior of mice in LS.Results: When glutamatergic neurons of LS were activated,the time to explore the central region in the open field significantly reduced,the number of times to enter the central region decreased,and the immobile time increased.The freezing behavior of mice in the elevated plus maze increased.In food and drink ingestion experiment,food intake decreased and water intake increased.In novelty-suppressed feeding experiment,the time stay in food area and entry numbers decreased,latency to feed increased.When glutamatergic neurons of LS were inhibited,the mice showed reverse anxiety-like behaviors compared to glutamatergic activation.When GABAergic neurons of LS were activated,in open field the time to explore the central region increased and the freezing time reduced.In the elevated plus maze,the time staying in open arms increased and the freezing behavior decreased.In food and drink ingestion experiment,food intake increased and water intake decreased.In novelty-suppressed feeding experiment,the time staying in food area and entry numbers increased,latency to feed decreased.When GABAergic neurons of LS were inhibited,the mice showed reverse anxiety-like behaviors compared to GABAergic activation.By retrograde and anterograde tracing,dopaminergic projections from VTA and LTDg to LS were revealed.Immunofluorescence staining showed dopamine D2 receptor expression in LS neurons.After administration of dopamine receptor antagonist in LS,the time to explore central region in the open field reduced,the moving speed decreased,and the immobile time increased.The time to stay inthe open arm decreased,freezing time increased and moving speed decreased in the elevated plus maze.In food and drink ingestion experiment,food intake decreased and water intake increased.In novelty-suppressed feeding experiment,the time stay in food area and entry numbers decreased,latency to feed increased.The sugar preference index reduced after dopamine receptor antagonist administration.After administration of dopamine receptor agonist in LS,the time to explore central region in the open field and the moving speed both increased.The time to stay in the open arm increased,freezing time and immobile time decreased in the elevated plus maze.In food and drink ingestion experiment,water intake decreased.In novelty-suppressed feeding experiment,the time stay in food area and entry numbers increased,latency to feed decreased.The sugar preference index increased after dopamine receptor agonist administration.Conclusion: LS was involved in the regulation of anxiety-like behavior in mice.The activation of glutamatergic neurons in LS led to anxiety-like behaviors in mice,which increased the degree of anxiety,while the inhibition of glutamatergic neurons led to the decrease of anxiety-like behaviors and decreased the degree of anxiety in mice.The activity of GABAergic neurons in LS correlated inversely with anxiety level in mice.The dopaminergic neurons regulated anxiety-like behaviors by acting on the LS dopamine receptors.Activation of dopamine receptors in LS alleviated anxiety in mice.