Lesson 11: Neuropharmacology Flashcards
Psychoactive Drugs
Psychoactive drugs affect the functioning of the synapses in the brain.
These changes can be excitatory, resulting in an increase in post synaptic
transmission or inhibitory, resulting in a decrease in post synaptic
transmission.
Excitatory drugs include Nicotine, Cocaine, and Amphetamines.
Inhibitory drugs include Benzodiazepines (Valium), Alcohol and
tetrahydrocannabinol (THC)
Stimulant Drugs
Stimulants act by mimicking the effects of the sympathetic nervous system.
They act to increase synaptic transmission and increase heart rate, blood
pressure and body temperature.
Examples of Stimulant Action
Pramipexole is used during the early stages of Parkinson’s disease to reduce
the effects of insufficient dopamine secretion. Can also be used as an
anti-depressant.
Pramipexole mimics dopamine by binding to the dopamine receptors in post
synaptic neurons at dopaminergic synapses.
Unlike most drugs that mimic neurotransmitters, Pramiplexole works as an
agonist because it causes the same effect as dopamine.Cocaine also acts at dopaminergic synapses.
Cocaine binds to dopamine reuptake transporters (membrane proteins that
pump dopamine back into the presynaptic neuron) allowing dopamine to
build up in the synaptic cleft resulting in the postsynaptic neuron being
constantly stimulated.
Cocaine gives feelings of euphoria.
MDMA (Ecstasy)
MDMA (ecstasy) is a recreational drug known to increase
the activity of specific neurotransmitters – serotonin and
dopamine
Serotonin (5-HT) is found in regions of the brain associated
with sleep and emotion and is involved in regulating mood
Dopamine is involved in the brain’s reward pathway and
plays an important role in regulating motivation and
pleasure
MDMA binds to reuptake pumps and increases the release
of neurotransmitter whilst slowing its rate of uptake
This causes an overstimulation of post-synaptic receptors
until neurotransmitter reserves are depleted
Long-term usage of MDMA can cause adverse changes to
brain architecture and result in cognitive impairment
Examples of Sedative Action
Diazepam (Valium) is a sedative that reduces anxiety, panic attacks and
insomnia. Can also be used as a muscle relaxant.
Diazepam binds to an allosteric site on GABA receptors in postsynaptic
neurons.
GABA is an inhibitory neurotransmitter causing hyperpolarization by opening
chloride channels allowing chloride ions into the cell.
When Diazepam is bound, increased rate of chloride entry occurs resulting in
inhibited nerve impulses in the postsynaptic neuron.
Tetrahydrocannabinol (THC) is found in cannabis.
THC binds to cannabinoid receptors in the presynaptic membrane which
inhibits the release of excitatory neurotransmitters.
Cannabinoid receptors are found in many parts of the brain including the
cerebellum, hippocampus cerebrum.
THC causes disruption of psychomotor behaviour, short term memory
impairment, intoxication and appetite stimulation.
Anaesthetics
Anaesthetics cause a reversible loss of sensation in all or part of the body.
Anaesthetics act by interfering with the neural transmission from pain
receptors to the CNS.
Anaesthetics bind to receptors in the pain pathways blocking the pain
signal from reaching the CNS
General anaesthetics induce unconsciousness while local anaesthetics
block receptors in the area of injection.
Drug Addiction
The causes of drug addiction are difficult to determine and
include genetics, environment and dopamine.
Genetics
Vulnerability to drug addiction based on a person’s genes is known as
genetic predisposition.
A gene, known as DRD2 may have a role to play in drug addiction.
The gene codes for dopamine receptor proteins.
This gene is controlled by multiple alleles
People who are homozygous for the A2 allele have been shown to
consume more alcohol than those with one or more copies of the A1
allele.
Environment
Social environment greatly affects the likelihood of taking drugs and
becoming addicted.
Peer pressure, poverty and social deprivation, traumatic life experiences and
mental health problems all contribute to increased likelihood of taking
drugs.
Cultural traditions often play a role and help explain why different drugs are
problems in different parts of the world.
Dopamine Secretion
Many addictive drugs affect dopamine secreting synapses.
Addictive drugs cause prolonged periods with high dopamine levels which lead to feelings of well-being and pleasure.
