Receptors fuel addiction

There is now evidence that nicotine receptors accumulate in the brain of a smoker like cigarette butts in an ashtray.

A team of Yale researchers have recently quantified the incidence and consequences of smoking on the health of the human brain.

Lead researcher Julie Staley, a professor of psychiatry and diagnostic radiology, said she and her team measured the activity in the sites of nicotine receptors — nicotinic acetylcholine receptors, or nAChr — in the brains of smokers and nonsmokers through imaging technology.

“We looked at exactly where nicotine is received in the brain and realized that there is still nicotine in the brains of smokers, even four to nine days after the date of their last cigarette,” Staley said. “On average, you can say that it takes about one week for all the nicotine to leave the brain.”

To observe these trends, Staley said her team helped their subjects quit smoking at least for the time they were involved in the study. There was a distinct correlation between the number of days since the subject’s last cigarette and the amount of nicotine receptors in the brain, she said.

“There were more blank receptors in the brain as time went on in the brain of a smoker,” she said. “This probably causes withdrawal.”

Staley said this was concluded by observing the positive correlation between nAChr and the urge to smoke to relieve withdrawal symptoms essentially by filling the empty nicotine receptor.

Staley said the procedure itself is significant because it is the first time that anyone was able to quantify the receptors. The researchers first documented the medical history of the smokers and tested the carbon monoxide content of their breaths, as well as screened urine for nicotine byproducts, to ensure that the study participants had refrained from smoking. The subjects were excluded from study if they were smoking at the time of experimentation.

The experiment used SPECT imaging to measure the flow of blood in the brain. Staley said a drug that was tied to radioactivity was injected into the subject and infused into the blood. Staley said that in this type of imaging, a scientist can more closely monitor the amounts of chemicals, as it is designed to be able to trace molecules in the body.

After the chemicals reached a steady state in the brain, the drugs bonded to the receptors and were quantitatively measured in the brain with SPECT technology. Staley said that the increase in the numbers of the receptors by the first week after the person quits smoking indicated that nicotine was still present in the brain after this period of time.

Now that her team can better image the brain of a smoker, Staley said, they will be able to do more studies on the effects smoking has on cognition as well as how abstinence or quitting smoking works in a neurobiological sense.

Frederic Bois, an associate research scientist in psychiatry, aided the comparison of the brains of the smokers with those of the nonsmokers by helping to produce the radio tracer used in the experiment. He said the information collected in this study may help smokers successfully quit in the future, in large part by giving them brand new information about its effects on the body.

“Ultimately, smoking is a huge public-health problem, and I do not think people see the repercussions of smoking on the brain,” Bois said.

But, regardless of the threat to health that smoking presents, one student smoker is willing to stand up for her smoking habit — one she calls the most consistent sensual experience she can have.

Chase Olivarius-Mcallister ’09, who started the Facebook group “Cigarettes Not Pregnancy,” said smoking is a choice she makes every day, and that she has the right to make such decisions.

“The point is that in America, smoking is the new scarlet letter,” Olivarius-Mcallister said.

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