DRUGS AND ALTERED
(this material is covered in „Drugs and Behaviour‟
section of chapter 4, Martin et al)
Room T10, William Guild Building
• The brain is protected by a tightly packed
lining of cells called the blood-brain
• However, some drugs are able to pass
through and influence the operation of the
• These drugs alter consciousness by
facilitating or inhibiting synaptic
Basic Steps in Synaptic
1. Neurotransmitters are synthesized in the
presynaptic (sending) neuron and stored in
2. Neurotransmitters are released into the synapse,
where they stimulate receptor sites on the
postsynaptic (receiving) neuron.
3. Neurotransmitters are deactivated by enzymes
or by reuptake.
Drugs that affect synaptic transmission can be
divided into two main categories:
• Agonist drugs
• Antagonist drugs
• Agonist drugs work by increasing the activity of
This can be done by:
• Enhancing a neuron‟s ability to synthesize,
store, or release neurotransmitters.
• Binding with and stimulating postsynaptic
receptor sites (or increasing sensitivity of these
• Prolonging activity of neurotransmitters (e.g., by
Example of Agonist Action
• The brain produces natural pain-killing
chemicals called endorphins.
• Drugs known as opiates (e.g., morphine,
codeine) have a molecular structure similar
to that of endorphins.
• Opiates can therefore bind to and activate
receptor sites that normally receive
endorphins, and duplicate their effects.
• Antagonist drugs work by inhibiting or
decreasing the action of neurotransmitters.
This can be done by:
• Reducing a neuron‟s ability to synthesize,
store, or release neurotransmitters
• Preventing a neurotransmitter from binding
with the postsynaptic neuron (e.g., by
blocking the receptor sites)
Example of Antagonist Action
• Symptoms of schizophrenia (hallucinations,
delusions etc.) are often associated with
abnormal overactivity of the
• „Antipsychotic‟ drugs have a molecular
structure similar enough to dopamine to
block the receptor sites, but not similar
enough to activate them.
• Depressants work by decreasing nervous
• In moderate doses depressants reduce
feelings of tension and anxiety, and produce
a state of relaxed euphoria.
• In high doses depressants can slow down
vital life processes to the point of death.
• Alcohol increases the activity of gamma-
aminobutyric acid (GABA), a major
• Alcohol also decreases the activity of
glutamate, which is a major excitatory
• Together these effects produce a
substantial reduction in neural firing
within the brain.
• Neural slowdown reduces activity in the
inhibitory control centres in the cerebral
• This leads to disinhibition and feelings of
• At higher dosage disruption of cerebral
control centres produces disorganised
thinking and physical coordination,
fatigue, and psychological depression.
• Alcohol also produces an effect known as
alcohol myopia (Steel & Josephs, 1990).
• Neural slowdown produces an increased
inability to attend to and process new
• Drinkers begin to pay attention only to those
aspects of a situation (cues) that stand out, and
ignore other relevant information.
• This produces an increase in risk-taking
behaviour and a failure to attend to long-term
consequences of actions (MacDonald et al.,
• Amphetamines can reduce appetite and fatigue,
decrease the need for sleep, and in some cases
reduce feelings of depression.
• Amphetamines increase the activity of the
neurotransmitters dopamine and norepinephrine.
• This is done by (a) causing the neuron to release
greater amounts of these neurotransmitters, and
(b) inhibiting reuptake.
• Adverse effects of amphetamines include
increased blood pressure, heart failure, cerebral
• Repeated high doses can result in long-term
brain damage (Diaz, 1997).
• Continuous heavy amphetamine use can result in
amphetamine psychosis (Lynn, 1971).
• Heavy amphetamine use is linked to severe
withdrawal symptoms (“crash”) due to
depletion of dopamine and norepinephrine
• Cocaine is a natural stimulant derived
from the coca plant (also synthetic version
• It produces excitation, sense of increased
muscular strength, and euphoria.
• Works by blocking reuptake of dopamine
• In large doses produces fever, vomiting,
convulsions, hallucinations, and paranoid
• Historically cocaine was hailed as a
“wonder drug” and widely used as a local
anaesthetic and general stimulant.
• In 1885 John Pemberton developed a
mixture of cocaine, syrup, and kola nut
extract and marketed it as health tonic.
• By 1891 there was a growing national
debate in the USA about the negative
aspects of cocaine.
• By 1902 Coca-cola contained only 1/400
of a grain of cocaine per ounce of syrup.
• Cocaine not completely removed until
• In 1943 Swiss chemist Albert Hofmann
accidentally absorbed a new chemical that he was
“The dizziness…became so strong at times that
I…had to lie down on a sofa…Everything in the
room spun around and the familiar objects and
pieces of furniture assumed grotesque, mostly
• Hoffman had synthesised lysergic acid
“We were somewhere around Barstow on the edge
of the desert when the drugs began to take hold.
I remember saying something like “I feel a bit
lightheaded; maybe you should drive…” And
suddenly there was a terrible roar all around us
and the sky was full of what looked like huge
bats, all swooping and screeching and diving
around the car, which was going about a
hundred miles an hour with the top down to Las
Hunter S. Thompson
Fear and Loathing in Las Vegas
• Hallucinogens are powerful
consciousness-altering drugs that produce
• Mescaline (peyote cactus extract)
• Psilocybin (“magic” mushrooms)
• Phencyclidine (“Angel Dust”)
• Hallucinogenic effects include distorted or
intensified sensory experience,
synaesthesia, “mystical” experiences and
• Adverse effects can include violent
outbursts, paranoia, panic, and
“flashbacks” long after the drugs‟ effects
have apparently ended.
• Molecular structure of LSD is very similar
to the neurotransmitter serotonin.
• Overall LSD decreases serotonin activity.
• During normal sleep decreased serotonin
levels are linked to the onset of REM
• Some argue that LSD‟s inhibition of
serotonin allows dreamlike altered
perceptions and hallucinations to emerge
while we are still awake (Trulson &
• Drugs can alter consciousness by
facilitating or inhibiting synaptic
transmission in the brain.
• Agonist drugs increase the activity of
• Antagonist drugs inhibit or decrease the
activity of neurotransmitters.