The "reward center" of the brain is more responsive to alcohol when estrogen levels are higher, according to new study published in PLOS One. The research findings could lead into insights about the development of addiction in women.

The ventral tegmental area of the brain, also known as the "reward center," releases dopamine in response to pleasurable sensations.

In response to something good, like chocolate, neurons in this area fire more rapidly. Eventually, even the sight of, or just the thought of, chocolate can result in quicker neuronal firing. This can sometimes lead to addiction.

"We knew from previous studies that female mice drink more alcohol than male mice and that the ovarian hormone estrogen promotes increased drinking by female mice. This suggested to us that estrogen might directly increase the activity of neurons in the “reward center” of the brain," Amy Lasek, assistant professor of psychiatry in the University of Illinois at Chicago College of Medicine, said to ALN.

Over 200,000 million women die as a result of alcoholism in the United States each year, according to data from the National Council of Alcoholism and Drug Dependence. Additionally, women tend to become addicted faster than men.

The research team studied the ventral tegmental areas of female laboratory mice to learn more about the relationship between estrogen, alcohol, and the "reward center" of the brain. These mice were naturally cycling, which meant that the animals went through normal estrous cycles similar to the menstrual cycle in women.

The researchers stored the ventral tegmental areas of female mice that were in either estrus or diestrus in special chambers that kept them alive. Laboratory mice in diestrus have estrogen levels 10 times higher than mice in estrus, which is when ovulation occurs.

Alcohol was then added to the chambers and neuronal activity was monitored with electrodes.

The neurons in the ventral tegmental areas of the diestrus mice were twice as active as the neurons of the mice in estrus when exposed to alcohol.

When estrogen was blocked, there was a significant drop in neuronal activity in the mice in diestrus compared to neurons where estrogen receptors remained functional. There was no change in activity in the mice in estrus.

"Our results suggest that women may be more vulnerable to developing an alcohol use disorder. There is some evidence that women progress from moderate drinking to problematic drinking more quickly than males, and estrogen may be a factor in this process," Lasek added.

"Overconsumption of alcohol by women has adverse effects on health, including increasing the risk of breast cancer. We hope that our research will give a greater understanding of how women develop alcohol use disorder and thus find better ways to prevent and treat alcohol use disorder in women."