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Absence of Specific Serotonin Receptor During Development Linked to Aggression and Impulsivity in Adults—Neuroscience 2013

Blocking serotonin receptors during development results in highly aggressive and impulsive behavior, according to new animal research. Reintroducing the receptors in adulthood suppresses impulsivity, but not aggression, to normal levels. These and related findings were described during a press conference on Sunday, November 10, at Neuroscience 2013, the annual meeting of the Society for Neuroscience and the world’s largest source of emerging news about brain science and health. 30,000 scientists are attending this convention in San Diego. Previous studies have identified a link between low serotonin levels and impulsive, violent aggression. However, therapeutic treatments that used antidepressants to increase serotonin generally did not reduce the negative behaviors. New research, led by Katherine Nautiyal, Ph.D., from Columbia University, identified a specific serotonin receptor (5-HT1B)(see image) as a key factor in aggressive and impulsive behaviors. Mice lacking this receptor during development exhibited more frequent and intense fighting than did control mice. They were also more impulsive in neutral situations, more vulnerable to abusing drugs, and demonstrated less restraint, even when rewarded to do so. Understanding the impact of changes in specific prefrontal regions during brain development could lead to new treatments and earlier interventions for disorders in which impulsivity plays a key factor. The research may have implications for understanding and dealing with aggressive and troublesome behaviors. The new findings show that: the absence of serotonin receptors during early development leads to highly aggressive and impulsive behaviors in mice. Impulsivity, but not aggression, returns to normal levels by reintroducing the receptors (Katherine Nautiyal, Ph.D., abstract 754.07); adolescents react more impulsively to danger than adults or children, and the prefrontal cortex works harder to exert control over impulsive responses to threatening cues (Kristina Caudle, Ph.D., abstract 852.14). “Violence is a pervasive societal problem with few effective treatments available, and violence and impulsivity often go hand-in-hand,” said Dr. Nautiyal. “Our research illuminates a new path for the development of medicines to treat disorders in which impulsivity is a key factor — including pathological gambling, suicide, and drug addiction.” Other recent findings discussed at the press conference show that: weak control of the brain’s prefrontal cortex (which monitors personality, decision-making, and self-restraint) over regions associated with reward and motivation could explain the lack of self-control experienced by anti-social individuals (Joshua Buckholtz, Ph.D., presentation 194.01); criminal defendants increasingly use brain science to explain their actions, pointing to brain scans and the scientific literature for evidence that brain impairments affect behavior. This is impacting how the legal system assigns responsibility and punishment for criminal wrongdoing in the United States (Nita Farahany, J.D., Ph.D., presentation 301); research further revealed that a lack of the 5-HT1B serotonin receptor during the early postnatal developmental period leads to aggressive and impulsive behavior. Interestingly, the impulsivity but not the aggression could be suppressed when the receptor levels were returned to normal in adult mice. This suggests that 5-HT1B expression during development is required for the formation of brain circuits that promote non-aggressive, more serene, behavior. The scientific presentation of this research will be delivered on Wednesday, November 13, in the time period 10–11 a.m. PST. “Our deeper understanding of the origins of delinquent behavior can be a double-edged sword,” said press conference moderator B.J. Casey, Ph.D., of Weill Cornell Medical College, an expert in attention, behavior, and related brain disorders. “While we’re making tremendous gains in neuroscience that should lead to improved treatments, our biological insights also have implications for criminal cases and the judicial process that we need to understand.” Neuroscience 2013 continues through Wednesday, November 13. [Neuroscience 2013 Program] [Society for Neuroscience 2013 meeting]