Speed, meth, chalk, crystal, ice, and glass are all names for the
drug methamphetamine. Methamphetamine comes in many different forms
and is snorted, swallowed, injected, or smoked. The smokable form
is known as "ice" or "crystal," due to its appearance.
Methamphetamine is a powerful drug. It acts by changing how the
brain works. It also speeds up many functions in the body. Methamphetamine
has a chemical structure that is similar to another drug called
amphetamine that I explore in my magazine on stimulants. Methamphetamine
can cause lots of harmful things, including inability to sleep,
paranoia, aggressiveness, and hallucinations.
No matter how methamphetamine is used, it eventually ends up in
the bloodstream where it is circulated throughout the brain. Methamphetamine
can affect lots of brain structures, but the ones it affects the
most are the ones that contain a chemical called dopamine. The reason
for this is that the shape, size, and chemical structure of methamphetamine
and dopamine are similar.
Your brain is made up of billions of nerve cells (or neurons). Neurons
come in all shapes and sizes, but most have three important parts:
a cell body that contains the nucleus and directs the activities
of the neuron; dendrites, short fibers that receive messages from
other neurons and relay them to the cell body; and an axon, a long
single fiber that carries messages from the cell body to dendrites
of other neurons.
Axons of one neuron and the dendrites of a neighboring neuron are
located very close to each other, but they don't actually touch.
Therefore, to communicate with each other they use chemical messengers
known as neurotransmitters. When one neuron wants to send a message
to another neuron it releases a neurotransmitter from its axon into
the small space that separates the two neurons. This space is called
a synapse. The neurotransmitter crosses the synapse and attaches
to specific places on the dendrites of the neighboring neuron called
receptors. Once the neurotransmitter has relayed its message, it
is either destroyed or taken back up into the first neuron where
it is recycled for use again.
There are many different neurotransmitters, but the one that is
most affected by methamphetamine is dopamine. Dopamine is sometimes
called the pleasure neurotransmitter because it helps you feel good
from things like playing soccer, eating a big piece of chocolate
cake, or riding a roller coaster. When something pleasurable happens,
certain axons release lots of dopamine. The dopamine attaches to
receptors on dendrites of neighboring neurons and passes on the
pleasure message. This process is stopped when dopamine is released
from the receptors and pumped back into the neuron that released
it where it is stored for later use.
Usually neurons recycle dopamine. But methamphetamine is able to
fool neurons into taking it up just like they would dopamine. Once
inside a neuron, methamphetamine causes that neuron to release lots
of dopamine. All this dopamine causes the person to feel an extra
sense of pleasure that can last all day. But eventually these pleasurable
effects stop. They are followed by unpleasant feelings called a
"crash" that often lead a person to use more of the drug.
If a person continues to use methamphetamine, they will have a difficult
time feeling pleasure from anything. Imagine no longer enjoying
your favorite food or an afternoon with your friends.
Because it is similar to dopamine, methamphetamine can change the
function of any neuron that contains dopamine. And if this weren't
enough, methamphetamine can also affect neurons that contain two
other neurotransmitters called serotonin and norepinephrine. All
of this means that methamphetamine can change how lots of things
in the brain and the body work. Even small amounts of methamphetamine
can cause a person to be more awake and active, lose their appetite,
and become irritable and aggressive.
Methamphetamine also causes a person's blood pressure to increase
and their heart to beat faster.
Scientists have discovered that even three years after long-time
methamphetamine users had quit using the drug, their dopamine neurons
were still damaged. Scientists don't know yet whether this damage
is permanent, but this research shows that changes in the brain
from methamphetamine use can last a long time. Research with animals
has shown that the drug methamphetamine can also damage neurons
that contain serotonin. This damage also continues long after the
drug use is stopped.
These changes in dopamine and serotonin neurons may explain some
of the effects of methamphetamine. If a person uses methamphetamine
for a long time, they may become paranoid. They may also hear and
see things that aren't there. These are called hallucinations. Because
methamphetamine causes big increases in blood pressure, someone
using it for a long time may also have permanent damage to blood
vessels in the brain. This can lead to strokes caused by bleeding
in the brain.
Source: National Institute on Drug Abuse
NIH Publication No. 97-4038