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Nearly 15% of all men and 30% of all women admit to a craving for chocolate.
Over 300 substances have been identified in chocolate. Some of these, including caffeine and theobromine (another, less powerful stimulant) could actually cause dependency effects. But the amounts of these substances in chocolate are too small to really have any effect.
The same goes for phenylethylamine, a substance related to a family of stimulants called amphetamines. For example, chocolate contains less phenylethylamine than goat cheese.
Anandamide, a neurotransmitter produced naturally by the brain, has also been isolated in chocolate. The neural receptors for anandamide are the same ones to which THC, the main active ingredient in cannabis, binds. The anandamide in chocolate might therefore contribute to the feeling of well-being reported by “chocoholics” (though you would have to eat well over 30 kilos of chocolate to experience effects comparable to one dose of cannabis!).
Be that as it may, many scientists agree that dependency on chocolate could simply be due to its taste, which causes a sensation of intense pleasure that people want to repeat.
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| HOW DRUGS AFFECT NEUROTRANSMITTERS |
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Dopamine appeared
very early in the course of evolution and is involved in many functions
that are essential for survival of the organism, such as motricity,
attentiveness, motivation, learning,
and memorization. But most of all, dopamine is a key element
in identifying natural rewards for the organism. These natural
stimuli such as food and water cause individuals to engage in approach
behaviours. Dopamine is also involved in unconscious memorization
of signs associated with these rewards.
It has now been established that all substances that trigger dependencies
in human beings increase the release of a neuromediator, dopamine,
in a specific area of the brain: the
nucleus accumbens. 
But not all drugs increase dopamine levels in the brain in the
same way.
- Some substances imitate natural
neuromediators and take their place on their receptors. Morphine,
for example, binds to the receptors for endorphin (a natural "morphine" produced
by the brain), while nicotine binds to the receptors for acetylcholine.
- Other substances increase the secretion of
natural neuromediators. Cocaine, for example, mainly increases
the amount of dopamine in the synapses, while ecstasy mainly
increases the amount of serotonin.
- Still other substances block a natural neuromediator.
Alcohol, for example, blocks the NMDA receptors.
Click on the names of each of the
following drugs to read about how they work and what effects
they have.
Alcohol ----- Opiates
(heroin, morphine, etc.) ----- Cocaïne ----- Nicotine
Caffeine ----- Amphetamines ----- Cannabis ----- Ecstasy ----- Benzodiazepines
Cocaine
Cocaine acts by blocking the reuptake
of certain neurotransmitters such as dopamine, norepinephrine,
and serotonin. By binding to the transporters that normally
remove the excess of these neurotransmitters from the synaptic
gap, cocaine prevents them from being reabsorbed by the
neurons that released them and thus increases their concentration
in the synapses (see animation). As a result, the natural
effect of dopamine on the post-synaptic neurons is amplified.
The group of neurons thus modified produces the euphoria
(from dopamine), feelings of confidence (from serotonin),
and energy (from norepinephrine) typically experienced
by people who take cocaine.
In addition, because the norepinephrine neurons in the
locus coeruleus project their axons into all the main structures
of the forebrain, the powerful overall effect of cocaine
can be readily understood.
In chronic cocaine consumers, the brain comes to rely on
this exogenous drug to maintain the high degree of pleasure
associated with the artificially elevated dopamine levels
in its reward circuits. The postsynaptic membrane can even
adapt so much to these high dopamine levels that it actually
manufactures new receptors. The resulting increased sensitivity
produces depression and cravings if cocaine consumption
ceases and dopamine levels return to normal.
Dependency on cocaine is thus closely related to its effect
on the neurons of the reward circuit.
General links about cocaine:
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