Substance Abuse and Drug Addiction Flashcards
What do drugs of abuse increase?
extracellular concentration of dopamine in the nucleus accumbens
What acts on the ventral tegmental area (VTA)?
drugs and behaviours such as eating, sex and social interaction
What does the VTA do?
produce dopamine and send it to the nucleus accumbens and the prefrontal cortex
What is the nucleus accumbens?
the pleasure centre of the brain that leads to rewarding feelings
What is the prefrontal cortex?
part of the brain responsible for emotions, learning and impulse control that helps the individual learn and repeat behaviours that lead to rewarding feelings
What is experimental evidence for reward circuit involvement of dopamine?
- rats trained to press lever for electrical stimulation to certain brain regions
- when electrode placed in reward circuit (e.g. VTA or NAcc), rat keeps pressing lever because of pleasure elicited by dopamine release
- effect lost if electrode is placed outside reward circuit or if dopamine release is blocked
What is a drug?
a substance which has a physiological effect when ingested or otherwise introduced into the body
What is a drug of abuse?
a drug that has no medical function or is taken at doses higher than would be required for therapy or homeostasis
What do all drugs of abuse result in?
significant toxicities both with short and long-term use
What is drug addiction?
a state characterised by compulsive use of a substance resulting in physical, psychological or social harm to the user and continued use in spite of the harm
What is tolerance?
diminished psychoactive effects of a drug after repeat use
How does tolerance feed addiction?
users take increasing amounts of a drug to get the desired effect
What is drug dependence?
an adaptive state that develops from repeated drug use and results in withdrawal symptoms upon cessation of drug use
What does psychological dependence appear as?
a craving for the drug; may not cause physical harm but can lead to drug-seeking behaviour
What is withdrawal?
when an individual becomes physically dependent on a drug and their bodies become less capable of functioning normally without it
What are withdrawal effects often?
opposite to the effects of the drug itself
Give examples of withdrawal symptoms
- feelings of fatigue and depression in cocaine withdrawal
- aches and pains with opioid withdrawal
What does artificial dopamine flooding do?
bypass normal controls which leads to a stronger and more prolonged activation of dopamine receptors
What can excessive stimulation of dopamine receptors do?
alter the brain’s reward system, reducing sensitivity to natural rewards and increasing the desire for repeated exposure to the triggering substance or behaviour, which can contribute to addiction
What are the 6 main types of drugs of abuse?
- stimulants e.g. cocaine, amphetamines
- depressants e.g. alcohol, barbiturates
- hallucinogens e.g. LSD, MDMA
- narcotics (opiates) e.g. opium, heroin
- cannabionols e.g. marijuana
- inhalants e.g. glue
What are acute effects of cocaine?
- intense feelings of euphoria within 3-5 mins
- increased alertness, elation and energy
- increased sexuality
How does cocaine act?
by blocking the reuptake of neurotransmitters like dopamine, noradrenaline, and serotonin in the brain which enhances their signalling and prolongs their effects
What are the local anaesthetic properties of cocaine?
it blocks sodium channels which prevents nerve conduction and causes a numbing sensation in the applied area
What is the half life of cocaine and amphetamine respectively?
- cocaine - 50-90mins
- amphetamine - 5-10hrs
What are acute effects of amphetamine?
diminished fatigue, increased alertness and reduced appetite
What is the time of onset of amphetamine?
- injected - immediate
- inhaled - <5 mins
- ingested - >20 mins
What are other forms of amphetamine?
- methamphetamine – can cause the feeling of euphoria and so has a high risk of dependence
- MDMA – can increase energy and sociability and alter perception of facilitated communication
What can amphetamine be used to treat and how?
- asthma – bronchodilation
- ADHD – increases attention and focus
- narcolepsy – increases attention, focus and wakefulness
- obesity – dopamine and noradrenaline regulate appetite and food intake; adrenaline suppresses appetite
What is the mechanism of action of amphetamine?
it blocks dopamine uptake by inhibiting MAOs which enhances release of dopamine from nerve terminals and vesicles
What is amphetamine a substrate of?
dopamine transporter (chemical similar to the natural neurotransmitters dopamine and noradrenaline)
What does amphetamine do once inside the cell?
it interferes with the vesicular monoamine transporter (VMAT) and impedes the filling of synaptic vesicles, so vesicles are depleted and cytoplasmic dopamine increases
What are narcotics?
pain-relieving drugs with strong addictive properties
What are the 3 types of narcotics?
- natural e.g. opium, morphine, codeine
- semi-synthetic e.g. herion
- synthetic e.g. methadone, fentanyl
What are acute effects of opiates?
pain relief, euphoria, sedation, relief of anxiety and depression of cough reflex
What are withdrawal effects of opiates?
dilated pupils, nausea, vomiting, diarrhoea and yawning
What is the mechanism of action of opiates?
they bind to the opioid receptor on the GABA-producing interneurons resulting in the inhibition of GABA release and an increase in dopamine release
What are medicinal therapeutics of marijuana?
increased appetite, attenuation of nausea, decreased intraocular pressure and relief of chronic pain
What is the active ingredient in marijuana?
delta-9-tetrahydrocannabinol (THC)
What is hashish/hash?
more potent than marijuana with similar effects also derived from the resin of the female plant
What is the onset time of marijuana?
5-10 mins to last for 1-4hrs
What are acute effects of marijuana?
- feeling high or pleasant sensation
- loss of coordination
- memory, judgment, and perception impairment
How does THC act?
it mimics an endogenous cannabinol called anandamide which binds to cannabinoid CB1 receptor to inhibit the release of GABA which allows increased binding of neurotransmitters to their receptors
What is the reward circuit made up of?
VTA, nucleus accumbens and prefrontal cortex
