Science

Drugs and the Brain: Individual Drugs and their Effects

Drugs and the Brain

Many people seem to have a constant desire to alter their
state of consciousness using drugs. They use stimulant
drugs to help them stay awake and dance the night away.
Others use sedatives to calm their nerves. Or even
substances that enable them to experience new forms of
consciousness and to forget the troubles of everyday life.
All of these drugs interact in different ways with
neurotransmitter and other chemical messenger systems
in the brain. In many cases, the drugs hijack the natural brain
systems that have to do with pleasure and reward –
psychological processes that are important in eating,
drinking, sex, and even learning and memory.

The Path to Addiction and Dependence

Drugs that act on the brain or the blood supply of the brain
can be invaluable – such as those that relieve pain.
Recreational drug use has a very different purpose, and the
problem with it is that it can lead to abuse. The user can, all
too easily, become dependent or even addicted. He or she
will then suffer very unpleasant physical and psychological
withdrawal symptoms when they interrupt their drug habit.
This state of dependence can lead a user to crave the drug,
even though doing so is clearly damaging to their work, health
, and family. In extreme cases, the user may be drawn into
crime in order to pay for the drug.
Fortunately, not everyone who takes a recreational drug
becomes dependent on it. Drugs differ in their dependence
liability – ranging from high risk in the case of cocaine, heroin
and nicotine to lower risk in the case of alcohol, cannabis,
ecstasy and amphetamines. During the development of drug dependence the body and brain slowly adapt to the repeated
presence of the drug, but exactly what changes go on in the
brain remain mysteries. Although the primary sites of action
of heroin, amphetamines, nicotine, cocaine and cannabis are
all different, these drugs share an ability to promote the
release of the chemical messenger dopamine in certain brain
regions. Although this is not necessarily akin to triggering a
“pleasure” mechanism, it is thought that the drug-induced
release of dopamine may be an important final common
pathway of “pleasure” in the brain. It represents the signal
that prompts a person to carry on taking the drug.

Individual Drugs – How they work and
the hazards of taking them.

Alcohol

Alcohol acts on neurotransmitter systems in the brain to
dampen down excitatory messages and promote the inhibition of
neural activity. Alcohol’s action proceeds through stages of
relaxation and good humor, after one drink, through to
sleepiness and loss of consciousness. That is why the police
are so strict about drinking and driving, and why there is so
much public support for this strict attitude. Some people
become very aggressive and even violent when they drink, and
about one in ten of regular drinkers will become dependent
alcoholics. Long-term alcohol use damages the body,
especially the liver, and can cause permanent damage to the
brain. Pregnant mothers who drink run the risk of having
babies with damaged brains and low IQ’s. More than 30,000
people die every year in Britain from alcohol-related diseases. Cannabis smokers tend to develop lung diseases and they
run the risk of developing lung cancer – although this has not
yet been proved. About one in ten users may become
dependent, which people who sell the drug are well aware of.
Repeated heavy use is incompatible with the skill of driving
and with intellectually demanding work; experiments have
established that people intoxicated with cannabis are unable
to carry out complex mental tasks. Although not yet proven,
there is some evidence that heavy use by young people might
trigger the mental illness schizophrenia (see p.51) in
susceptible individuals.

Nicotine

Nicotine is the active ingredient in all tobacco products.
It acts on brain receptors that normall recognizese the
neurotransmitter acetylcholine; it tends to activate natural
alerting mechanisms in the brain. Given this, it’s not
surprising that smokers say that cigarettes help them
concentrate and have a soothing effect. The trouble is that
nicotine is highly addictive and many inveterate smokers
continue to smoke for no better reason than to avoid the
unpleasant signs of withdrawal if they stop. The pleasure
has long gone. While there appears to be no deleterious
effect on the brain, tobacco smoke is extremely damaging
to the lungs and long-term exposure can lead to lung cancer
and also to other lung and heart diseases. More than
100,000 people die every year in Britain from smoking-related diseases.

Cannabis

Cannabis presents us with a puzzle, for it acts on an
important natural system in the brain that uses neurotransmitters that are chemically very like cannabis. This system
has to do with the control of muscles and regulating pain
sensitivity. Used wisely, and in a medical context, cannabis
can be a very useful drug. Cannabis is an intoxicant which can
be pleasurable and relaxing, and it can cause a dream-like
state in which one’s perception of sounds, colors and time
is subtly altered. No-one seems to have died from an overdose, although some users may experience unpleasant panic
attacks after large doses. Cannabis has been used at least
once by nearly half the population of Britain under the age of
30. Some people believe it should be legalized – and doing so
could cut the link between the supply of the drug and that of
other much more dangerous drugs. Unfortunately, as with
nicotine, smoking is the most effective way of delivering it to
the body. Cannabis smoke contains much the same mixture of poisons as cigarettes (and is often smoked with tobacco).

Amphetamines

Amphetamines are man-made chemicals that include
“Dexedrine”, “Speed”, and the methamphetamine derivative
called “Ecstasy”. These drugs act in the brain by causing the
release two naturally occurring neurotransmitters. One is
dopamine – which probably explains the strong arousal and
pleasurable effects of amphetamines. The other is serotonin
– which is thought to account for their ability to cause a
sense of well-being and a dream-like state that can include
hallucinations. Dexedrine and Speed promote mainly
dopamine release, Ecstasy more serotonin. The even more
powerful hallucinogen d-LSD also acts on serotonin mechanisms
in the brain. Amphetamines are powerful
psychostimulants and they can be dangerous – especially in
overdose. Animal experiments have shown that Ecstasy can
cause a prolonged, perhaps permanent reduction of
serotonin cells. This might account for the “mid-week blues”
suffered by weekend ecstasy users. Every year, dozens of
young people die after taking it. Frightening schizophrenia-like psychosis can happen after Dexedrine and Speed. You
might be lured into thinking that Speed could help you in an
exam – but don’t. It won’t.

Heroin

Heroin is a man-made chemical derivative of the plant
product morphine. Like cannabis, heroin hijacks a system in
the brain that employs naturally occurring neurotransmitters known as endorphins. These are important in pain
control – and so drugs that copy their actions are very
valuable in medicine. Heroin is injected or smoked whereupon
it causes an immediate pleasurable sensation – possibly due
to an effect of endorphins on reward mechanisms. It is highly
addictive, but, as dependence develops, these pleasurable
sensations quickly subside to be replaced by an incessant “craving”. It is a very dangerous drug that can kill in even
modest overdose (it suppresses breathing reflexes). Heroin
has ruined many people’s lives.

Cocaine

Cocaine is another plant-derived chemical which can cause
intensely pleasurable sensations as well as acting as a
powerful psychostimulant. Like the amphetamines, cocaine
makes more dopamine and serotonin available in the brain.
However, like heroin, cocaine is a very dangerous drug. People
intoxicated with it, especially the smoked form called “crack”,
can readily become violent and aggressive, and there is a life-threatening risk of overdose. The dependence liability is high,
and the costs of maintaining a cocaine habit draw many
users into crime.

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