Diverging neural pathways assemble a behavioural state from separable features in anxiety

Abstract

Behavioural states in mammals, such as the anxious state, are characterized by several features that are coordinately regulated by diverse nervous system outputs, ranging from behavioural choice patterns to changes in physiology (in anxiety, exemplified respectively by risk-avoidance and respiratory rate alterations). Here we investigate if and how defined neural projections arising from a single coordinating brain region in mice could mediate diverse features of anxiety. Integrating behavioural assays, in vivo and in vitro electrophysiology, respiratory physiology and optogenetics, we identify a surprising new role for the bed nucleus of the stria terminalis (BNST) in the coordinated modulation of diverse anxiety features. First, two BNST subregions were unexpectedly found to exert opposite effects on the anxious state: oval BNST activity promoted several independent anxious state features, whereas anterodorsal BNST-associated activity exerted anxiolytic influence for the same features. Notably, we found that three distinct anterodorsal BNST efferent projections-to the lateral hypothalamus, parabrachial nucleus and ventral tegmental area-each implemented an independent feature of anxiolysis: reduced risk-avoidance, reduced respiratory rate, and increased positive valence, respectively. Furthermore, selective inhibition of corresponding circuit elements in freely moving mice showed opposing behavioural effects compared with excitation, and in vivo recordings during free behaviour showed native spiking patterns in anterodorsal BNST neurons that differentiated safe and anxiogenic environments. These results demonstrate that distinct BNST subregions exert opposite effects in modulating anxiety, establish separable anxiolytic roles for different anterodorsal BNST projections, and illustrate circuit mechanisms underlying selection of features for the assembly of the anxious state.

CGRP antagonist infused into the bed nucleus of the stria terminalis impairs the acquisition and expression of context but not discretely cued fear

“…To dissect out the individual contributions of these areas, more advanced techniques, such as optogenetic stimulation, will be especially valuable. In fact, results from the first such studies have now been reported (Jennings et al 2013;Kim et al 2013). Findings from Kim et al (2013) are especially relevant to this discussion.…”

“…In fact, results from the first such studies have now been reported (Jennings et al 2013;Kim et al 2013). Findings from Kim et al (2013) are especially relevant to this discussion. Their results are consistent with what we and others have found (i.e., that the BNST as a whole promotes anxiety), as determined in their laboratory by the anxiolytic effects on plus-maze behavior of intra-BNST NBQX + AP5 infusions (i.e., an ionotropic glutamate receptor antagonist cocktail).…”

Principles of designing interpretable optogenetic behavior experiments

“…Thus, empirical determination of expression at different time points after initiation of expression may be of use. For example, it is not uncommon to perform experiments with mice 4 wk after viral delivery (e.g., by AAV), but many groups wait six or more weeks for opsin expression to reach distal axons of an infected cell (Ciocchi et al 2010;Witten et al 2010 Felix-Ortiz et al 2013;Kim et al 2013), though in cholinergic neurons virally infected at a young age, just 3 wk were reported to be effective for axonal expression .…”

High-resolution and cell-type-specific photostimulation mapping shows weak excitatory vs. strong inhibitory inputs in the bed nucleus of the stria terminalis

“…The BNST coordinates neuroendocrine, autonomic and somatomotor responses to anxiety and emotional aspects of stressful events, and it is identified as a key node in neural networks relevant to pathological anxiety and addiction. This area has received increased attention in light of recent physiological and functional studies (Daniel and Rainnie 2016;Deisseroth 2014;Jennings et al 2013;Johansen 2013;Kim et al 2013).Based on gross anatomical and cytoarchitecture features, the BNST contains a collection of nuclei, and they can be generally divided into anterior and posterior groups by the presence of anterior commissure (Wood and Swann 2005). A number of studies have focused on the anterior dorsal BNST (adBNST) for robust identification and delineation of this region.…”

“…The extent of strong inhibitory connections is consistent with earlier findings showing that GABAergic neurons make up a predominant portion of the general makeup of adBNST and glutamatergic neurons only account for a minority of the overall population (Daniel and Rainnie 2016;Larriva-Sahd 2006;Nguyen et al 2015). Given that BSNT receives strong extrinsic excitatory inputs from the amygdala and other brain regions (Daniel and Rainnie 2016;Kim et al 2013), strong local inhibitory connections can play an important role in modulation of these extrinsic inputs.Because both the detailed neuronal morphology revealed by biocytin staining and input mapped profiles were available, we explored the spatial relationship between dendritic fields and input profiles by examining their overlays, as illustrated in Fig. 4.…”