Alcohol
Alcohol acts on neurotransmitter systems in the brain to
dampen down excitatory messages and promote inhibition of
neural activity. Alcohol’s action proceeds through stages of
relaxation and good humour, 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.
Nicotine
Nicotine is the active ingredient in all tobacco products.
Nicotine acts on brain receptors that normally recognise 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 smokingrelated
diseases.
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 schizophrenialike
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 lifethreatening
risk of overdose. The dependence liability is high,
and the costs of maintaining a cocaine habit draw many
users into crime.
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, colours 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 legalised - and doing so
could cut the link between 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 cigerettes (and is often smoked with tobacco).
