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Secret behind nic-sickness could help break tobacco addiction: An aversive dopamine network in brain activated by high-dose nicotine could be targeted to help people kick the habit

If you remember your first hit on a cigarette, you know how sickening nicotine can be. Yet, for many people, the rewards of nicotine outweigh the negative effects of high doses.

University of California, Berkeley, researchers have now mapped out part of the brain network responsible for the negative consequences of nicotine, opening the door to interventions that could boost the aversive effects to help people quit smoking.

Though most addictive drugs at high doses can cause physiological symptoms that lead to unconsciousness or even death, nicotine is unique in making people physically ill when inhaled or ingested in large quantities. As a result, nicotine overdoses are rare, though the advent of e-cigarettes has made “nic-sick” symptoms like nausea and vomiting, dizziness, rapid heartbeat and headaches more common.

The new research, conducted in mice, suggests that this aversive network could be manipulated to treat nicotine dependence.

“Decades of research have focused on understanding how nicotine reward leads to drug addiction and what are the underlying brain circuits. In contrast, the brain circuits that mediate the aversive effects of nicotine are largely understudied,” said Stephan Lammel, UC Berkeley associate professor of molecular and cell biology. “What we found is that the brain circuits that are activated after a high aversive dose are actually different from those that are activated when nicotine is delivered at a low dose. Now that we have an understanding of the different brain circuits, we think we can maybe develop a drug so that, when nicotine is taken at a low dose, these brain circuits can be coactivated to induce an acute aversive effect. This could actually be a very effective treatment for nicotine addiction in the future, which we currently do not have.”

Lammel and Christine Liu, who recently obtained her Ph.D. from UC Berkeley, also found that nicotine receptors in the reward pathway become desensitized by high doses of nicotine, which probably contributes to the negative experience of high doses.

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