Antidepressant Increases Amygdala Activity: Discovery offers more clues to understanding how brain function contributes to mental illness

Abnormalities in the amygdala (an almond-shaped group of brain cells that processes information about emotional events) may be linked to depression, anxiety and post traumatic stress disorders.  While existing research suggests that variations in serotonin levels impact the amygdala, scientists have yet to discover how amygdala function is regulated, or methods to control the changes that may lead to illnesses such as depression.

A new study published by Vice President of Research Dr. Bruce Pollock and colleagues used intravenously administered citalopram (part of a class of antidepressants called a selective serotonin reuptake inhibitor, SSRI, that increases the level of serotonin in the brain) to investigate how immediate changes in serotonin levels impact amygdala function. 

The scientists gave either citalopram or a placebo to healthy volunteers, showed the participants different facial expressions, and measured the their amygdala activity in response to the different expressions using fMRI technology.  The scientists discovered that participants had an increase in amygdala activity in direct relationship to the antidepressant's concentration. This pattern of amygdala activity caused by increased serotonin levels may help explain how SSRIs achieve an antidepressant effect i.e. first stimulating the amygdala, which then becomes less active. Intriguingly, the data may also reveal a mechanism contributing to clinical observations of extreme agitation, restlessness, and suicidal ideation in some individuals when starting SSRI treatment.

Dr. Pollock and colleagues’ discovery adds to the development of a comprehensive model of how changes in serotonin affect brain function.  Understanding how medications affect the brain processes over time is essential to understanding how medications can be made safer and more effective.

For more information, visit  Acute 5-HT Reuptake Blockade Potentiates Human Amygdala Reactivity

 

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