(Videos displaying aggressive behavior of Pet-1 knockout mice can be viewed at http://neurowww.cwru.edu/faculty/deneris.shtml; click Movies Link.)
Other neurologic functions, such as motor coordination, feeding, and locomotor activity, do not appear altered in the knockout mouse.
Anxiety and aggression are normal and important behaviors that allow individuals to respond appropriately to threats or cope with a challenging environment. However, it is clear that uncontrollable or excessive anxiety and aggression can be counterproductive.
"The behavior of Pet-1 knockout mice is strikingly reminiscent of some human psychiatric disorders that are characterized by heightened anxiety and violence," says Evan Deneris, Ph.D., principal investigator of the study and a neuroscientist at CWRU. The study is published in the Jan. 23 issue of the science journal Neuron.
Previously, Deneris' lab showed that in the brain Pet-1 is active only in serotonin nerve cells or neurons, a relatively small number of cells (among the trillions of neurons in a human brain, only a few hundred thousand produce serotonin) that profoundly affect emotions. Serotonin is a chemical that acts as a messenger or neurotransmitter allowing neurons to communicate with one another in the brain and spinal cord. It is important for ensuring an appropriate level of anxiety and aggression. Defective serotonin neurons have been linked to excessive anxiety, impulsive violence, and depression in humans.