Rodents subjected to prolonged social isolation show anxiety, and behaviours suggesting an inability to feel pleasure, reports a study online this week in Nature Neuroscience. The paper shows that these depression-like symptoms can be treated with some antidepressants and provides new information about the way in which drug treatment reduces anxiety symptoms.
Eric Nestler and colleagues find that rats and mice housed alone in cages and denied social interaction show depressive behaviours such as abnormal sexual behaviour, decreased preference for sugar water and anxious behaviour. They also find that this prolonged stress decreases the activity of a key protein called CREB in the nucleus accumbens shell, a brain region that is known to be involved in our response to motivational and emotional stimuli. Long-term, but not short-term, treatment with a tricyclic antidepressant was able to reverse these behaviors and restored the levels of CREB.
This work not only provides an animal model for depression based on prolonged social isolation, but also provides a new mechanism by which antidepressant treatment alleviates anxiety symptoms.