Smokers, pay attention! Nicotine is not only bad for the lungs, but also makes smokers more prone to taking risks and alters the brain's reward system, according to a study published by Sweden's Sahlgrenska Academy on Monday.

The reward system is a collection of brain structures and neural pathways that are responsible for reward-related cognition, including reinforcement learning, incentive salience, and pleasure.

Using around 100 rats, researchers at the Sahlgrenska Academy at the University of Gothenburg studied the effects of nicotine on the brain and behavior. The study lasted for seven months and showed extensive alterations in the reward system of the rodents' brains.

"We were very surprised. We did not expect to see such long-lasting impacts," researcher Julia Morud Lekholm told Swedish Television. "Nicotine appears to cause a cascade of effects that get worse and worse over time," she said.

Half the lab rats were given a saline solution and half were given nicotine for three weeks. Three months into the experiment, the rats who had been given nicotine showed signs of no abstinence and appeared to be fearless and more prone to risky behavior.

They were placed in a constructed environment consisting of a maze where two areas were more open and more brightly lit. The rats that had been given nicotine were more prone to venture into those more unprotected areas of the maze.

In another experiment, around 30 rats were put down after seven months so that the researchers could study their brains. They discovered significant alterations in the brains of the rats that had consumed nicotine. Their GABA systems, which usually halt dopamine and the signaling to the brain's nerve cells, instead had the opposite function. This led the researchers to conclude that nicotine impacts what is commonly known as the brain's reward system, which is similar in rats and humans.

According to Julia Morud Lekholm of the University of Gothenburg, this signals that smokers' reward systems are shifted so that "the next time you use a drug your response may be much stronger compared to someone who hasn't used a drug."

(With inputs from Xinhua)