Tobacco smokers may tend to see their habit as not being very healthy, but they don't realize they use a drug. Is it a drug? When a team checked what happened in the brain while smoking or taking opiate drugs (poppy-derived ones, like morphine, heroin, dihydromorphine, hydromorphone, anmain, codeine, thebaine, and papaverine), the results told an interesting story.

The new study published in the "The Journal of Neuroscience" shows that both nicotine and opiates impact the brain's reward system (the nucleus accumbens, connected to pleasure sensing areas) with the same strength.

"Testing rat brain tissue, we found remarkable overlap between the effects of nicotine and opiates on dopamine signaling within the brain's reward centers," said co-author Daniel McGehee, Associate Professor in Anesthesia & Critical Care at the University of Chicago Medical Center.

His team tested how dopamine, a key neurotransmitter, was involved in reward and addiction. Dopamine synthesis is boosted in neural centers like the nucleus accumbens, by naturally rewarding actions like food, sex (yeah, food and sex are addictive, when pleasant), some drugs, and the neutral factors that we associate with them (like the perfume of your lover with sex).
Nicotine and opiates have very different chemical structures, but their effect on the dopamine system is almost the same.

"There is a specific part of the nucleus accumbens where opiates have been shown to affect behavior, and when we tested nicotine in that area, the effects on dopamine are almost identical," said McGehee.

This research has completed previous work showing an overlapped action of the two types of drugs on the physiology of the ventral tegmenal area, another important segment of the brain's reward circuitry. New treatments against addiction could target both types of drugs.

"It also demonstrates the seriousness of tobacco addiction, equating its grip on the individual to that of heroin. It reinforces the fact that these addictions are very physiological in nature and that breaking away from the habit is certainly more than just mind over matter," said McGehee.