Effects of social isolation traced to brain hormone

The anxiety and aggression that result from social isolation have been traced to altered levels of an enzyme that controls production of a brain hormone.

The study, done in mice by researchers at the University of Illinois at Chicago College of Medicine, is reported in this week's online addition of the Proceedings of the National Academy of Sciences.

"We use this animal model for human stress because social isolation in both animals and humans can be responsible for a range of psychological effects, including anxiety, aggression and memory impairment," said Dr. Erminio Costa, director of the UIC Psychiatric Institute, professor of biochemistry and one of the authors of the study.

Previous studies had suggested that the neural pathways that underlie aggression, anxiety and fear include activation of specific types of neural circuitry that leads into the amygdala, the region of the brain responsible for emotion.

The researchers looked in these types of neurons for changes in the levels of two enzymes that are needed for the production of allopregnanolone, a brain hormone that acts to reduce stress through regulation of GABA, an important neurotransmitter. They found that the level of one of the enzymes, called 5-alpha-reductase type I, was reduced nearly 50 percent in the lonesome mice. Levels of the other enzyme did not change.

The researchers suggest that the decrease of 5-alpha-reductase type I and the consequent reduction in the hormone may impair the function of circuits leading to the amygdala and explain the aggressive behavior, perhaps related to anxiety, in socially isolated mice.

"Humans respond to similar stress in very similar ways," said Dr. Alessandro Guidotti, UIC scientific director and professor of biochemistry in psychiatry. "By identifying the mechanism we may be able to identify drugs that can treat these effects of stress."

UIC researchers Roberto Agis-Balboa, Dr. Graziano Pinna, Fabio Pibiri and Dr. Bashkim Kadriu also contributed to the study. The work was supported by grants from the National Institute of Mental Health. Pibiri was supported in part by a postdoctoral fellowship from the Regione Autonoma della Sardegna, Italy.

UIC ranks among the nation's top 50 universities in federal research funding and is Chicago's largest university with 25,000 students, 12,000 faculty and staff, 15 colleges and the state's major public medical center. A hallmark of the campus is the Great Cities Commitment, through which UIC faculty, students and staff engage with community, corporate, foundation and government partners in hundreds of programs to improve the quality of life in metropolitan areas around the world.

Source: University of Illinois at Chicago

Related stories:

Pregnancy not turning minds to mush: Study
Pregnancy and motherhood may make us all go a little gooey, but it's not turning mums' brains into mush, according to mental health researchers at The Australian National University.
Learned safety cheers depressed mice: An animal model of behavioral intervention for depression
A new animal model has provided insight into the cellular and molecular mechanisms associated with behavioral therapy for depression. The study, published by Cell Press in the October 9th issue of Neuron, may provide a good model system for testing cellular and molecular interactions between antidepressive medications and behavioral treatments for depression.
Learning how not to be afraid
Why do some people have the ability to remain calm and relaxed even in the most stressful situations? New experiments in mice by Howard Hughes Medical Institute (HHMI) researchers are providing insight into how the brain changes when the animals learn to feel safe and secure in situations that would normally make them anxious.
Researchers propose minocycline as a promising drug for patients with Fragile X syndrome
A UC Riverside-led team of biomedical scientists has found that a readily available drug called minocycline, used widely to treat acne and skin infections, can be used to treat Fragile X syndrome, the most common inherited cause of mental impairment and the most common cause of autism.
Millisecond brain signals predict response to fast-acting antidepressant
Images of the brain's fastest signals reveal an electromagnetic marker that predicts a patient's response to a fast-acting antidepressant, researchers have discovered.
Coming soon: Self-guided, computer-based depression treatment
Self-guided treatment for depression could soon be only a mouse click away. Scientists with the National Space Biomedical Research Institute (NSBRI) are developing an interactive, multi-media program that will assist astronauts in recognizing and effectively managing depression and other psychosocial problems, which can pose a substantial threat to crew safety and mission operations during long-duration spaceflights.
Mapping the neuron-behavior link in Rett Syndrome
A link between certain behaviors and the lack of the protein associated with Rett Syndrome – a devastating autism spectrum disorder – demonstrates the importance of MeCP2 (the protein) and reveals never-before recognized functions associated with aggression and obesity, said researchers at Baylor College of Medicine in a report in the current issue of the journal Neuron.
The neuropeptide Y system is linked to a more severe form of alcohol dependence
Previous animal research showed an association between the neuropeptide Y (NPY) pathway and its three receptor genes and response to alcohol and cocaine. A new study has examined the relationship of the human NPY system with alcohol dependence (AD), with and without withdrawal symptoms, and cocaine dependence. Two receptor genes in particular, NPY2R and NPY5R, were found to be associated with a more severe subtype of AD – characterized by withdrawal symptoms or coexisting alcohol and cocaine dependence – and cocaine dependence.

News discussion:

General Science news