Nicotine found to block oestrogen production in women's brains

Swedish researchers have found that one dose of nicotine, equivalent to that found in a single cigarette, blocks oestrogen production in women’s brains. Their work was presented at the 35th European College of Neuropsychopharmacology (ECNP) Congress in Vienna this month, and may explain several behavioural differences in women who smoke — including why they are more resistant than men to quitting smoking.

It has been known for some time that women and men respond differently to nicotine, with women being more resistant to nicotine replacement therapy, and showing a greater tendency than men to relapse when trying to quit smoking. However, the biological basis for these differences has not previously been understood.

The researchers, from Uppsala University, worked with a group of 10 healthy female volunteers. The women were given a commercially available nicotine dose intranasally, and at the same time were injected with a radioactive tracer attached to a molecule that binds to the enzyme aromatase, which is responsible for the production of oestrogen. MRI and PET brain scans enabled the researchers to visualise both the quantity of aromatase and where it was located in the brain. The researchers found that a single dose moderately reduced the amount of aromatase in the brain.

“For the first time, we can see that nicotine works to shut down the oestrogen production mechanism in the brain of women,” said lead researcher Associate Professor Erika Comasco. “We were surprised to see that this effect could be seen even with a single dose of nicotine, equivalent to just one cigarette, showing how powerful the effects of smoking are on a woman’s brain.”

The effect was shown in the thalamus, which is part of the limbic system in the brain. This system is involved in behavioural and emotional responses.

“This is a newly discovered effect, and it’s still preliminary work,” Comasco said. “We’re still not sure what the behavioural or cognitive outcomes are, only that nicotine acts on this area of the brain; however, we note that the affected brain system is a target for addictive drugs, such as nicotine.

“There are significant differences in the way men and women react to smoking. Women seem to be more resistant to nicotine replacement therapy, they experience more relapses, show greater vulnerability for heritability of smoking and are at greater risk of developing primary smoking-related illnesses, such as lung cancer and heart attacks. We need now to understand if this action of nicotine on the hormonal system is involved in any of these reactions.

“Of course this is a comparatively small group of women; we need a larger sample to confirm these findings. Nevertheless, the message is that nicotine has various effects on the brain, including on the production of sex hormones such as oestrogen.”

Image credit: iStock.com/skynesher

Please follow us and share on Twitter and Facebook. You can also subscribe for FREE to our weekly newsletters and bimonthly magazine.