Psychiatric Disorders, Drug Action and Addiction Flashcards
What are drugs?
Tend to imitate substances already present in our nervous system, particularly those that affect transmission at the synapse
Why do drugs tend to imitate substances already present in our nervous system
- Mainly from plants (e.g. nicotine - tobacco plant)
- The plant produces these chemicals to attract insects, to stop being eaten etc., or for own processes
Name the 2 ways that drugs affect transmission at the synapsy
- Antagonist
- Agonist
Describe an Antagonistic drug
- Inhibit transmission at the synapse
- Block neurotransmitter
Describe an Agonistic drug
- Facilitate transmission at the synapse
- Increase effects of neurotransmitter, or mimic the neurotransmitter
How much affinity do drugs have?
Drug has a high affinity for a receptor if it binds to that receptor
How much efficacy do drugs have?
Drug has a high efficacy if it has a tendency to activate that receptor
What do most drugs stimulate?
Most drugs stimulate the release of dopamine
Particularly in the nucleus accumbens
Define the nucleus accumbens
small subcortical area rich in dopamine receptors
How do drugs work?
(diagram)
Name 2 stimulants?
> Amphetamine (Speed)
> Cocaine
What does Speed do?
Stimulates dopamine synapses by increasing the release of dopamine from presynaptic terminal
What does Cocaine do?
Blocks the reuptake of dopamine, thus prolonging effects
Why are stimulants followed by a crash?
Dopamine washes away, can’t be replaced quick enough
Name 2 Opiates
> Morphine
> Heroine
How do Opiates work?
- Inhibits GABA, so increases dopamine
- Also blocks a hindbrain area that usually releases norepinepherine
What does Marijuana consist of
> Contains cannabinoids
> Bind to specific cannabinoid receptors (widespread in the brain)
What does marijuana do to the brain?
- Inhibit GABA release (increase in dopamine release in nucleus accumbens) = perception of heightened awareness
- Cannabinoid receptors abundant in hypothalamus (feeding!) = increased appetite
How do the functioning of drugs relate to addiction?
- Many addictive substances increase activity at dopamine synapses
- Particularly in the nucleus accumbens
What is the difference between liking and wanting drugs?
Drugs increase ‘need’ for the substance even if the experience is not pleasant
- Mice with increased dopamine production showed no more pleasure in food, but made more effort to get it
- Mice with decreased dopamine production made less effort to get food, but ate just as much.
(Kalat)
How does the sensitization of the nucleus accumbens relate to drugs?
– Becomes more sensitive to substances after repeated use
– Increased ability to release dopamine in response to the substance
– Reduced sensitivity to other things
How does the withdrawal symptoms of drugs relate to addiction
– Cravings for the drug
– Relapse causes increased sensitivity
– User learns that the drug relieves distress associated with withdrawal, and so craves it more during future withdrawal
Name something that can counter addiction
Varenicline (CHAMPIX), treatment for smoking
What is the functio of valenicline
Partial nicotine receptor agonist.
Stimulates and binds the nicotine agonist