A new study has revealed that social isolation may change the way the brain works, leading to increased alcohol consumption among males.
Researchers from Northwestern University and the Salk Institute for Biological Studies identified a neural pathway that appears to play a direct role in this behavior in male mice, while isolation led to a decrease in alcohol consumption in females.
The researchers placed adult male and female mice in social groups, then moved some of them into solitary cages to simulate social isolation, while keeping other mice in groups to serve as a control group.
For about two weeks, the researchers gave the mice a daily one-hour opportunity to choose between water and a solution containing 15% alcohol.
The results showed that isolated male mice gradually increased their alcohol consumption, while females decreased it. This finding prompted scientists to investigate the changes that occur in the brain as a result of isolation.
The team monitored the activity of specific brain cells as mice moved and chose between water and alcohol. They found that social isolation activated a neural pathway connecting two brain regions: the lateral basal amygdala, associated with processing emotions and stress, and the medial prefrontal cortex, involved in decision-making and regulating behavior.
Richa Patel, assistant professor of general psychiatry and neuroscience at Northwestern University's Feinberg School of Medicine and lead author of the study, said the research pointed to a specific brain circuit that explains how social isolation can lead to increased alcohol consumption in males.
To determine whether this pathway is merely a response to alcohol consumption or whether it actually contributes to increased consumption, the researchers used "optogenomics" technology, which allows for the control of the activity of specific nerve cells using light.
When researchers artificially activated the circuit in unisolated male mice, they began responding to alcohol in a similar way to the isolated mice. Conversely, deactivating the circuit in the isolated mice led to a decrease in their alcohol consumption
These results suggest that the activity of this neural circuit may be a direct factor in the increased alcohol consumption associated with isolation, and not simply a consequence of drinking.
Researchers are still unable to explain why males and females respond differently to social isolation. They believe that hormones or differences in the way neural circuits function may be factors that explain this disparity.
The team plans to study what makes this circuit hyperactive during social isolation, and whether other brain regions play a role in increased alcohol consumption.
The researchers are also trying to find out if the mechanism they discovered in mice can help explain the effect of loneliness and social isolation on alcohol consumption in humans, as the study is still in the pre-clinical stage and does not prove that the same mechanism can occur in humans.
