Luis Pennanen studied behaviors in mice to better understand the neurobiology of suicide with his AFSP Postdoctoral Fellowship. While there is no animal model for suicidal behavior, studies of animals may help us to learn more about the neurobiology underlying suicidal behavior. Serotonin, a brain neurotransmitter that has been found to be to be associated with suicide attempts and suicide, can be more easily studied in mice than living people. In his 2013 paper in Neuropsychopharmacology, Dr. Pennanen reported on serotonin and behavior in normal mice and mice that have altered serotonin genes.
Over 90% of people who die by suicide have a diagnosable psychiatric disorder at the time of death, yet many psychiatric patients never attempt suicide. A stressor may trigger acute worsening of the psychiatric disorder that may lead to suicidal behavior. Studies of suicide attempters have shown that loss of the ability to inhibit behavior has been linked to impulsiveness and lack of flexibility of thinking, both identified as prevalent among people who have made a suicide attempt. The serotonin system has been identified as a key factor in brain function related to behavioral control and decision-making. Dr. Pennanen studied decision-making and cognitive flexibility in mice whose serotonin 5-HT2c gene had been partially blocked so that amounts of available serotonin were lower. These mice are called 2CKO mice. He compared them with mice without the genetic change, called Wild Type (WT).
He found that both types of mice could learn simple tasks that required them to make a choice or to reverse their learning. When the mice were faced with more difficult tasks the 2CKO mice demonstrated impaired attention and inability to learn to make choices and reverse what they had learned as well as being more impulsive. The impaired decision-making and lack of flexibility were not found to be related to motivation or interest in reward. From Dr. Pennanen’s study we learn that serotonin has profound effects on behaviors related to suicide attempts and perhaps suicide.
Luis Pennanen, Ph.D., is a Scientist at the University of Tubingen, Deutsches Zentrum für Neurodegenerative Erkrankungen (German Center for Neurodegenerative Diseases within the Helmholtz Association) in Bonn, Germany. Click here to read more about Dr. Pennanen's Postdoctoral Research Fellowship.
Published article from this study:
- Pennanen, L., van der Hart, M., Yu, L., & Tecott, L. H. (2013). Impact of serotonin (5-HT)2C receptors on executive control processes. Neuropsychopharmacology, 38(6), 957-967.