‘Nicotine memories’ from teen years may lead to alcoholism in later years
Smoking brings with it not only a high risk of cancers, heart disease and stroke: A Tel Aviv University study has found that exposure to nicotine in tobacco during adolescence can lead to increased alcohol intake in adulthood.
The researchers, led by Dr. Segev Barak and his team at Tel Aviv University’s School of Psychological Sciences and the Sagol School of Neuroscience, suggest that memories of smoking tobacco as a teenager alter the brain’s reaction to alcohol even after prolonged nicotine abstinence. Their study was recently reported in the journal Scientific Reports. The findings indicate that these nicotine “memories” may even lead to a tendency toward heavier drinking later in life.
Researchers have long known that there is a link between nicotine and alcohol consumption. But the nature of the connection – how long it lasts, which causes which – has remained a mystery.
“Previously, it was believed that the mere consumption of nicotine during adolescence could trigger the use of other drugs – cocaine, heroin and alcohol,” Barak said. “Our study shows that nicotine ‘memories’ from adolescence are the culprit, not the nicotine itself.”
The researchers found that such “memories” caused long-lasting changes in the brain, long after the cessation of nicotine consumption. A brief exposure to the nicotine environment triggered a robust decrease in the expression of the growth factor called GDNF in the brain’s pleasure center. “We have previously shown that GDNF serves as a brain regulator of alcohol consumption,” Barak said. “We assume that this drop in GDNF following the retrieval of nicotine memories leads to loss of control, thus boosting drinking.”
The researchers used rats to test the link between nicotine and alcohol consumption. They installed an experimental self-serve alcohol dispenser, operated by the press of a lever. When placed in this “bar,” rats were free to consume unlimited amounts of alcohol.
One group of rats received nicotine during adolescence in Chamber B, and then drank alcohol in adulthood in Chamber A – in other words, drinking alcohol in an environment different from that in which they used nicotine. Conversely, the second group also received nicotine during adolescence in Chamber A, but then in adulthood drank alcohol in the same chamber (that is, in the nicotine-associated environment), triggering a reminder of the nicotine experience.
In the US, 7% of adolescents (aged 12-17) and 35% of young adults (18-25) are tobacco users, and the likelihood of alcohol abuse is increased among such early-onset tobacco smokers. These associations are thought to reflect the capacity of alcohol and nicotine to enhance the motivation to obtain the other substance, as supported by studies in humans and rodents. In Israel, a large number of soldiers start smoking at 18 when they join the IDF, and many more smoke upon discharge than before they were drafted.
“The rats eagerly drank alcohol,” said Yossi Sadot-Sogrin, who contributed to the research. “During the daily one-hour sessions, most of them consumed the amount of alcohol equivalent to a glass or two of wine.” But when the self-serve alcohol dispenser was installed in the same chamber in which rats received nicotine during their adolescence, the amount of alcohol consumed rose sharply.
“In the nicotine-associated environment, rats drank the amount of alcohol that corresponded to four glasses of wine, and even more,” said Koral Goltseker, who collaborated on the study.
The team is currently researching the specific changes to the brain caused by nicotine memories. “If we can prevent these brain changes, we hope we can prevent the longterm increase in alcohol consumption,” concluded Barak. “It will also teach us a lot about the brain mechanisms that lead to alcoholism.”