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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.) ----- Cocaine ----- Nicotine
Caffeine ----- Amphetamines ----- Cannabis ----- Ecstasy ----- Benzodiazepines
Alcohol
Alcohol passes directly from the
digestive tract into the blood vessels. In minutes, the
blood transports the alcohol to all parts of the body,
including the brain.
Alcohol affects the brain’s neurons in several ways.
It alters their membranes as well as their ion channels,
enzymes, and receptors. Alcohol also binds directly to
the receptors for acetylcholine, serotonin, GABA, and the
NMDA receptors for glutamate.
Click on the labels in the diagram to the right to see
an animation about how alcohol affects a GABA synapse.
GABA’s effect is to reduce neural activity by allowing
chloride ions to enter the post-synaptic neuron. These
ions have a negative electrical charge, which helps to
make the neuron less excitable. This physiological effect
is amplified when alcohol binds to the GABA receptor, probably
because it enables the ion channel to stay open longer
and thus let more Cl- ions into the cell.
The neuron’s activity would thus be further diminished,
thus explaining the sedative effect of alcohol. This effect
is accentuated because alcohol also reduces glutamate’s
excitatory effect on NMDA receptors.
However, chronic consumption of alcohol gradually makes
the NMDA receptors hypersensitive to glutamate while desensitizing
the GABAergic receptors. It is this sort of adaptation
that would cause the state of excitation characteristic
of alcohol withdrawal.
Alcohol also helps to increase the release of dopamine,
by a process that is still poorly understood but that appears
to involve curtailing the activity of the enzyme that breaks
dopamine down.
General links about alcohol: |
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