Thirst Reduces Stress Response: “The Watering Hole Effect”


Assuming this is conserved in humans, the following passage might suggest that it’s better that you walk into an interview a little bit thirsty:

“We’re calling this the Watering Hole Effect,” says Eric Krause, PhD, a research assistant professor in the basic science division of UC’s department of psychiatry and behavioral neuroscience and first author of the study. “When you’re thirsty, you have to overcome some amount of fear and anxiety to approach a communal water source. And you want to facilitate those interactions—that way everyone can get to the water source.”

Krause and his team dehydrated laboratory rats by giving them sodium chloride, then exposed them to stress. Compared with a control group, the rats that received the sodium chloride secreted fewer stress hormones and also displayed a reduced cardiovascular response to stress.

“Their blood pressure and heart rate did not go up as much in response to stress as the control group’s, and they returned to resting levels more quickly,” says Krause.

“Also, in a social interaction paradigm with two rats interacting, we found them to be more interactive and less socially anxious.”

Further research, through examination of brain and blood samples from the rats, showed that the same hormones that act on kidneys to compensate for dehydration also act on the brain to regulate responsiveness to stressors and social anxiety.

The elevated sodium level, known as hypernatremia, limited stress responses by suppressing the release of the pro-stress hormone angiotensin II. Conversely, it increased the activity of oxytocin, an anti-stress hormone. (via.)

Thanks to hugthemonkey for pointing this one out on Twitter. Susan also posted a link to this interesting gem recently: A study led by Jillian O’Connor, a graduate student in the Department of Psychology, Neuroscience & Behaviour at McMaster University, found that people think they can predict whether a mate will cheat by listening to tone of voice.


Anabolic steroids, depression, BDNF & morning corticosterone levels


Abuse of anabolic androgenic steroids (AASs) is frequently associated with changes in mood, including depression. [...] We used male adult rats injected for 4 weeks with either nandrolone or stanozolol at daily doses (5 mg/kg, s.c.) that are considered equivalent to those abused by humans [...] AAS treatment reduced levels of brain-derived neurotrophic factor in the hippocampus and prefrontal cortex, reduced the expression of low-affinity glucocorticoid receptors in the hippocampus, and increased morning trough basal plasma corticosterone levels. All these changes have been related to the pathophysiology of major depressive disorder. Accordingly, rats treated with nandrolone or stanozolol showed an increased immobility time in the forced swim test, which is widely used for the screening of antidepressant drugs. All effects produced by AASs were prevented by co-administration with the classical antidepressant, chlorimipramine. (via.)


Tetris and its strange relationship with PTSD


In earlier laboratory work the Oxford team showed that playing Tetris after traumatic events could reduce memory flashbacks in healthy volunteers. These are a laboratory model of the types of intrusive memories associated with post-traumatic stress disorder (PTSD).

In this new experimental study, the researchers compared the effectiveness of Tetris at reducing flashbacks with Pub Quiz Machine 2008, a word-based quiz game. They found that whilst playing Tetris after viewing traumatic images reduced flashbacks by contrast playing Pub Quiz increased the frequency of flashbacks. [...]

In two separate experiments, the team showed a film to healthy volunteers that included traumatic images of injury from a variety of sources, including adverts highlighting the dangers of drink driving – a recognised way to study the effects of trauma in the laboratory.’ [...]

Our latest findings suggest Tetris is still effective as long as it is played within a critical six-hour window after viewing a stressful film,’ said Dr Emily Holmes of Oxford University’s Department of Psychiatry, who led the work. ‘Whilst playing Tetris can reduce flashback-type memories without wiping out the ability to make sense of the event, we have shown that not all computer games have this beneficial effect – some may even have a detrimental effect on how people deal with traumatic memories.’ (via.)


Exercise reverses anxiety phenotype in rats


Exercise can ameliorate anxiety and depression-like behaviours induced by an adverse early-life environment by altering the chemical composition in the hippocampus – the part of the brain that regulates stress response, researchers from UNSW have found. [...]

“What’s exciting about this is that we are able to reverse a behavioural deficit that was caused by a traumatic event early in life, simply through exercise,” said Professor of Pharmacology Margaret Morris, who will present the findings this week at the International Congress of Obesity in Stockholm.

In the study, rats were divided into groups and either isolated from their mothers for controlled periods of time to induce stress or given normal maternal contact. Half were given access to a running wheel.

In addition to being more anxious, animals that were subjected to stress early in life had higher levels of stress hormones and fewer steroid receptors in the part of the brain controlling behaviour.

“Both the anxious behaviour and the levels of hormones in these rats were reversed with access to the exercise wheel,” Professor Morris said.

“We know that exercise can elevate mood, but here we are seeing chemical changes that may underpin this improvement. One of these is increases in brain-derived neurotrophic factor (BDNF), which helps nerve cells grow. (via.)

In other news…
Morphine found to decrease testosterone in the brain, as well as liver, and testis. Which is interesting in light of the fact that a stressed/anxious phenotype of rat would have fewer steroid receptors in their brain.


Robert Sapolsky’s 52 minute Lecture on Depression


This is one of the best videos I’ve ever seen on the physiological roots of depression. This guy (Robert Sapolsky) really goes in-depth and connects the dots between scientific facts and common philosophy & anecdote. 52 minutes — not for the faint of heart.


Creativity, Depression, and DHEAS (a hormone that “blunts the effects of cortisol”)


Well, it turns out the cliché might be true after all: Angst has creative perks. That, at least, is the conclusion of Modupe Akinola, a professor at Columbia Business School, in her paper “The Dark Side of Creativity: Biological Vulnerability and Negative Emotions Lead to Greater Artistic Creativity.” The experiment was simple: She asked subjects to give a short speech about their dream job. The students were randomly assigned to either a positive or negative feedback condition, in which their speech was greeted with smiles and vertical nods (positive) or frowns and horizontal shakes (negative). After the speech was over, the subjects were given glue, paper and colored felt and told to create a collage using the materials. Professional artists then evaluated each collage for creativity.

In addition, Akinola also measured DHEAS (dehydroepiandrosterone), an endogenous hormone that blunts the effects of stress hormones like cortisol. (As I’ve written about before, depression is closely entangled with chronic stress.) Given this chemical power, it’s not surprising that low levels of DHEAS have been associated with susceptibility to volatile mood swings and downward spirals of sadness. Finally, subjects were also asked to self-report their moods, giving the scientists a subjective and objective measurement of how they were feeling, and how the feedback to the speech had shifted their emotional state.

Not surprisingly, positive feedback cheered us up: Participants who received smiles and nods during their speeches reported feeling better than before. Negative feedback had the opposite effect – it’s no fun having our dreams trampled on.

Here’s where things get interesting: People who received negative feedback created better collages, at least when compared to those who received positive feedback or no feedback at all. Furthermore, those with low baselines of DHEAS proved particularly vulnerable to the external effects of frowns, so that they proved to be the most creative of all. (via.)

Other interesting DHEAS tidbits: