We all know what it is like to feel anxious; sweaty palms, fast breathing and that wish to run away and hide.
In this month’s Neuropod Kerri Smith talks to Karl Deisseroth about his latest publication in which he and his colleagues describe how they have managed to tune anxiety responses in mice. By stimulating or inhibiting the activity in particular regions within a part of the brain called the bed nucleus of the stria terminalis (BNST), they were able make these mice behave in a more or less anxious way.
As with humans, anxiety was measured by breathing rate. They looked at how much time a mouse would spend in an light, open area compared to a dark, closed area (mice prefer dark, closed spaces, particularly when they are anxious).
The group divided this tiny nucleus and separated two subregions they wanted to study: the oval subregion and the anterodorsal subregion. They found that these subregions have opposite effects on anxiety. When they stimulated the anterodorsal region in a mouse they could reduce anxiety and when they inhibited it the anxiety would increase again. The oval region caused the opposite effect. Simulation lead to more anxious behaviours and inhibition led to less.
So it would seem these two subregions are acting in opposite ways to regulate anxiety. Stimulating the anterodorsal region reduced anxiety and stimulating the oval region increased it again.
In fact, when the group decided to record the activity in these areas they found that the anterodorsal region was more active when mice were in safe environments (ie. a dark compartment) than when they were in less safe environments (ie. an light, open space).
The group went even further to break down the different groups of neurons within the subregions that control breathing rate and exploratory behaviour. However, it would seem that not all anxiety related behaviours are controlled by the BNST as the group were unable to alter heart-rate by stimulating or inhibiting the nucleus.
There are lots of brain regions involved in anxiety, far more than mentioned in this article. The authors of this study want to go on to look at other networks that might control or be controlled by the BNST in order to develop a better understanding of how our anxiety response comes about.
So why does this matter? The hope is to help develop treatments for anxiety disorders (such as panic attacks, agoraphobia or post traumatic stress disorder) or to understand why some individuals develop anxiety disorders and others do not. But do we want to prevent anxiety? Or is anxiety nature’s way of reminding us that something is not quite right.