The brain’s synapses can adapt
to the chronic presence of a drug in various ways. For example,
in some cases, to try to compensate for the sudden increase
that a drug triggers in the concentration of a neurotransmitter,
the synapses reduce the number of receptors for this neurotransmitter.
In other cases, they simply make these receptors less sensitive
to this neurotransmitter, so that it binds to them less efficiently.
Both of these mechanisms are very common in chronic consumers
opiates, nicotine, and benzodiazepines.
This tolerance can also involve other organs besides the brain.
For example, in alcoholics, the liver becomes able to metabolize
more alcohol, thus reducing the amount that reaches the brain.
|HOW DRUGS AFFECT
A psychotropic is any substance that can
modify a person’s psyche, causing changes in his or her perceptions,
mood, consciousness, and so on.
Psychotropics can be classified in several different ways– for
example, according to their chemical structure, or the mechanisms
by which they act, or whether they are used recreationally or medically,
or whether they are legal or illegal. But in addiction research,
psychotropics are usually classified according to their pharmacological
effects on people’s nervous systems, because these effects
refer to a reality that is immediately perceptible.
In the 1970s, three major families of psychotropics were recognized
on the basis of these effects: depressants, stimulants, and hallucinogens.
Later classifications distinguished seven categories. The classification
presented here comprises five categories: the three groups just
mentioned, plus psychotherapeutic medications and steroids
(click on the name of each category
to read a description of it and a list of the main drugs within
Depressants ---- Stimulants ---- Hallucinogens ---- Psychotherapeutic
Medications ---- Steroids