"There is a clear relationship between a short form of the serotonin transporter and a very high vulnerability to develop clinical depression when people are exposed to increasing levels of stressful life events." says Dr. Bartolomucci, "This is one of the first studies performed in mice that only have about 50% of the normal activity of the transporter relative to normal mice, which is exactly the situation that is present in humans with high vulnerability to depression".

Mice with the genetic change were more likely to develop characteristics of depression and social anxiety, which researchers measure by their degree of activity and their response to meeting new mice. The work from this study now allows researchers to link the genetic changes that are present in humans with decreased serotonin turnover in the brain. It suggests that the genetic mutation impedes the removal of signaling protein from communication areas in the brain, which may result in an exaggerated response to stress.

Dr. Bartolomucci points out that many of the chemical changes they measured occurred in the areas of the brain that regulate memory formation, emotional responses to stimuli and social interactions, which might be expected. "What we were surprised by was the magnitude of vulnerability that we observed in mice with the genetic mutation and the selectivity of its effects".

Source: The Company of Biologists