High Estrogen Levels Make Women More Sensitive to Alcohol

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A new study carried out on mice at the University of Illinois confirms that the brain’s reward center is much more sensitive to the effects of alcohol when estrogen levels are high.  The research was led by assistant professor of psychiatry in the UIC College of Medicine, Amy Lasek and the findings were published online in the journal PLOS ONE.

What Lasek and the others discovered was that when estrogen levels were high, neurons found within the ventral tegmental area (also referred to as VTA or the reward center) region of the brain fired extremely fast.  According to their findings, this response is mediated in the VTA through tiny receptors on dopamine-emitting neurons.

“When estrogen levels are higher, alcohol is much more rewarding,” said Lasek.  “Women may be more vulnerable to the effects of alcohol or more likely to overindulge during certain stages of their cycle when estrogen levels are higher, or may be more likely to seek out alcohol during those stages.”  This study indicates that addiction is highly influenced by estrogen and that women are more likely to abuse alcohol and other drugs, particularly during times of anxiety or stress.

The brain’s VTA is partly there to asses whether something is good or valuable.  As neurons within the brain becomes stimulated, dopamine is released, creating euphoria as a result.  For example, when you experience something good, neurons in the VTA fire much quicker, producing the sensation in the brain that it’s nice and something to sought out again.

In regards to addiction, the nice experience is drugs or alcohol.  So as the VTA neurons fire more quickly the person gets more anxious about getting the drugs or alcohol.  Unfortunately this urge can be so strong that not even a friend, family, job, or health can steer them away from the wrong path.

As part of the study Lasek and her team used female mice to examine the relationship between estrogen, alcohol and the VTA.  First the mice were evaluated to determine at what point they were to enter diestrus, when the estrogen levels are near their highest.  “In mice in diestrus, estrogen levels increase to about 10 times higher than they are in estrus, the phase in which ovulation occurs and estrogen levels drop,” said Lasek.

After comparing VTAs from mice in both diestrus and estrus, the researchers found that activity levels increased twice as much in neurons of mice in diestrus compared to those in estrus.  The team then decided to block estrogen receptors on dopamine-sensitive neurons in VTA in mice while in both cycles.  What they found was with the blocker present, the alcohol response from the neurons was much lower than those neurons with normal estrogen receptor functioning.  Those mice in estrus were unaffected by the estrogen receptor blocker in terms of the response to alcohol in neurons.

“The increased reward response to alcohol we see when estrogen levels are high is mediated through receptors for estrogen in the VTA,” said Mark Brodie, co-author on the paper and professor of physiology and biophysics in the UIC College of Medicine.  According to Lasek, the increased sensitivity to alcohol in the VTA when estrogen levels are high could play a key role in addiction in women. “We already know that binge drinking can lead to lasting changes in the brain, and in women, those changes may be faster and more significant due to the interaction we see between alcohol, the VTA and estrogen,” she said.  “Binge drinking can increase the risk of developing alcoholism, so women need to be careful about how much alcohol they drink.”

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