Nos1+ and Nos1- excitatory neurons in the BLA regulate anxiety- and depression-related behaviors oppositely

Background: The basolateral amygdala (BLA) neurons are primarily glutamatergic and have been associated with emotion regulation. However, little is known about the roles of BLA neurons expressing neuronal nitric oxide synthase (nNOS, Nos1) in the regulation of emotional behaviors.Methods: Using Nos1-cre mice and chemogenetic and optogenetic manipulations, we specifically silenced or activated Nos1+ or Nos1- neurons in the BLA, or silenced their projections to the anterdorsal bed nucleus of the stria terminalis (adBNST) and ventral hippocampus (vHPC). We measured anxiety behaviors in elevated plus maze (EPM) and open-field test (OFT), and measured depression behaviors in forced swimming test (FST) and tail suspension test (TST).Results: BLA Nos1+ neurons were predominantly glutamatergic, and glutamatergic but not GABAergic Nos1+ neurons were involved in controlling anxiety-and depression-related behaviors. Interestingly, by selectively manipulating the activities of BLA Nos1+ and Nos1- excitatory neurons, we found that they had opposing effects on anxiety-and depression-related behaviors. BLA Nos1+ excitatory neurons projected to the adBNST, this BLA-adBNST circuit controlled the expression of anxiety-and depression-related behaviors, while BLA Nos1- excit- atoryneurons projected to vHPC, this BLA-vHPC circuit contributed to the expression of anxiety-and depression-related behaviors. Moreover, excitatory vHPC-adBNST circuit antagonized the role of BLA-adBNST circuit in regulating anxiety-and depression-related behaviors.Conclusions: BLA Nos1+ and Nos1-excitatory neuron subpopulations exert different effects on anxiety-and depression-related behaviors through distinct projection circuits, providing a new insight of BLA excitatory neurons in emotional regulation.Limitations: We did not perform retrograde labeling from adBNST and vHPC regions.