In a new study, researchers examined how inflammation contributes to opioid withdrawal and dependence.
The research was conducted by a team from Thomas Jefferson University.
Opioid dependence has become a national crisis with serious impact on economic and social welfare.
A big goal of ongoing research in combating opioid use disorder is understanding drug withdrawal.
The physical and emotional symptoms of withdrawal can be life-threatening and make up a powerfully negative experience; the fear of these symptoms strongly motivates addiction.
Previous research has shown opioids can cause inflammation in the brain by inducing immune cells to release inflammatory molecules called cytokines.
The main immune cells in the brain are microglia and astrocytes.
Inflammatory responses induced by opioids have been observed in the central amygdala, a brain region that has been strongly implicated in opioid dependence because of its role in emotion and motivation.
The central amygdala can also be affected by inflammation in other parts of the body, like the gut.
In fact, the communication between the gut and the brain can shape a variety of motivated behaviors and emotional states, including those linked to drug dependence and withdrawal.
In the study, the team isolated single neurons, microglia, and astrocytes from the central amygdala and studied their genetic profiles in normal, opioid-dependent, and withdrawn rats.
They found that the profile of astrocytes changed the most, shifting genetic expression to a more activated state. This shift correlated strongly with opioid withdrawal.
Furthermore, all three cell types showed an increase in an inflammatory cytokine called TNF alpha in withdrawn animals.
In addition, the researchers found that certain anti-inflammatory bacteria were suppressed in withdrawn animals, shifting the gut microbiota and causing a phenomenon which can lead to inflammation in the digestive system.
The authors say that the inflammation in the gut and central amygdala may be linked to the negative emotional experience of opioid withdrawal.
The findings suggest that inflammation in the gut and brain may exacerbate symptoms linked to opioid withdrawal.
Targeting inflammation in these regions may reduce the negative experience of drug withdrawal, and therefore prevent dependence.
The study is published in Frontiers of Neuroscience.
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