Modern research
shows that nicotine acts on the brain to produce a number of
effects. Specifically, its addictive nature has been found to
show that nicotine activates reward pathways—the circuitry
within the brain that regulates feelings of pleasure and
euphoria.
Dopamine is one of the key neurotransmitters actively involved
in the brain. Research shows that by increasing the levels of
dopamine within the reward circuits in the brain, nicotine acts
as a chemical with intense addictive qualities. In many studies
it has been shown to be more addictive than cocaine and heroin,
though chronic treatment has an opposite effect on reward
thresholds. Like other physically addictive drugs, nicotine
causes down-regulation of the production of dopamine and other
stimulatory neurotransmitters as the brain attempts to
compensate for artificial stimulation. In addition, the
sensitivity of nicotinic acetylcholine receptors decreases. To
compensate for this compensatory mechanism, the brain in turn
upregulates the number of receptors, convoluting its regulatory
effects with compensatory mechanisms meant to counteract other
compensatory mechanisms. The net effect is an increase in reward
pathway sensitivity, opposite of other drugs of abuse (namely
cocaine and heroin, which reduce reward pathway sensitivity).
This neuronal brain alteration persists for months after
administration ceases. Due to an increase in reward pathway
sensitivity, nicotine withdrawal is relatively mild compared to
ethanol or heroin withdrawal. Nicotine also has the potential to
cause dependence in many animals other than humans. Mice have
been administered nicotine and exhibit withdrawal reactions when
its administration is stopped. Gorillas have been forced to
smoke cigarettes by humans, and have similar difficulty
quitting.
A study found that nicotine exposure in adolescent mice retards
the growth of the dopamine system, thus increasing the risk of
substance abuse during adulthood.
There is only anecdotal evidence about abuse or addiction with
nicotine gum or nicotine patches.
Due to its stimulation of the nicotinic receptors (mimicking the
effects of acetylcholine) it has been reported as a useful tool
for the induction of lucid dreams, where a nicotine patch is
applied after 4–6 hours of normal sleep and the subject falls
back to sleep (into a more REM intense sleep cycle). Non-lucid
dreams may become vivid, more memorable and some report a higher
frequency of disturbing dreams. However it should be stressed
that a consistent use of nicotine will desensitize the nicotinic
receptors and therefore addicts are actually far less likely to
achieve lucid dreams.
Toxicology >>
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Nicotine
History and name
Chemistry
Pharmacology
1.Pharmacokinetics
2.Pharmacodynamics
2.1 In adrenal medulla
2.2 In CNS
Psychoactive effects
Dependence
Toxicology
Therapeutic uses
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