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Nicotine, like cocaine, heroin, and marijuana, increases the level of the neurotransmitter dopamine. Dopamine affects
the brain pathways that control reward and pleasure. Scientists now have located a molecule (the beta 2 (b2) subunit
of the nicotine cholinergic receptor) as a critical component in nicotine addiction. Mice that lack this subunit fail to self-administer
nicotine, implying that without the b2 subunit, the mice do not experience the positive reinforcing properties of nicotine.
This new finding identifies a potential site for targeting the development of nicotine addiction medications.
Another study found dramatic changes in the brain’s pleasure circuits during withdrawal from chronic nicotine use.
These changes are comparable to changes observed during the withdrawal from other abused drugs such as opiates,
cocaine, amphetamines, and alcohol. Scientists found significant decreases in the sensitivity of the brains of laboratory
rats to pleasurable stimulation after nicotine administration was abruptly stopped. These changes lasted several days and
may correspond to the anxiety and depression experienced by humans for several days after quitting smoking “cold turkey.”
The results of this research may help in the development of better treatments for the withdrawal symptoms that may interfere
with individuals’ attempts to quit smoking.
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