From the article:
“When estrogen levels are higher, alcohol is much more rewarding,” said Lasek, who is the corresponding author on the paper and a researcher in the UIC Center for Alcohol Research in Epigenetics. “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.”
Studies indicate that gender differences in psychiatric disorders, including addiction, are influenced by estrogen, one of the primary female sex hormones. Women are more likely to exhibit greater escalation of abuse of alcohol and other drugs, and are more prone to relapse in response to stress and anxiety.
[…]
“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,” Lasek said.
VTAs [ventral tegmental area - “reward center”] were taken from mice in both estrus and diestrus and kept alive in special chambers. Electrodes recorded the activity of individual dopamine-sensitive neurons in the VTA. Next, the researchers added alcohol to the chamber. Activity increased twice as much in neurons from mice in diestrus compared to the response of neurons from mice in estrus.
Lasek and her colleagues then blocked estrogen receptors on dopamine-sensitive neurons in VTA in mice in estrus and diestrus. With the blocker present, the response to alcohol in neurons from mice in diestrus was significantly lower compared with neurons where estrogen receptors remained functional. The estrogen receptor blocker reduced the alcohol response to levels seen in mice in estrus. The responses to alcohol in neurons from mice in estrus were unaffected by the estrogen receptor blocker.