News: Publication IPMC/J. Biological Psychiatry/Dr. Jacques BARIK/H.Marie_J.Barik Team
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Nicotine: much more than just an addictive molecule?
A new study reveals that nicotine – the psychoactive substance in tobacco – not only causes addiction, but it could also profoundly disrupt our motivation towards natural rewards, such as food, sex, or social interactions.
In mice exposed to prolonged nicotine consumption, our team observed an increased motivation to obtain palatable food, even if it did not provide greater pleasure. In other words, nicotine encourages action to obtain rewards, without increasing their taste.
This phenomenon is explained by an alteration in the functioning of certain brain circuits involved in motivation. In particular, nicotine weakens communication between an area called the laterodorsal tegmentum (LDT)) – which modulates another brain area called the ventral tegmental area (VTA) – known for its key role in the reward system. The VTA notably produces dopamine, a molecule associated with motivation and associative learning.
Normally, a third region of the brain, the’Lateral habenula (LHb), LHb exerts control over the LDT-VTA axis to regulate motivation. But in mice treated with nicotine, this "natural brake" is disrupted: LHb loses its control over LDT. The result: excessive motivation, directed towards natural rewards like food.
By reactivating these connections in the brain, we were able to normalize behaviors, thus establishing a causal link between dysregulation in this system and motivational exacerbation.
This work highlights a little-known effect of nicotine: it can amplify certain compulsive behaviors beyond tobacco use. This could help us better understand the links between smoking, eating disorders, and behavioral addictions such as pathological gambling.