Lecture 14: Substance abuse, dependence and treatments Flashcards
What is substance abuse according to the World Health Organization (WHO)?
Harmful or hazardous use of psychoactive substances, including alcohol and illicit drugs.
Define drug dependence
The body’s physical need or addiction to a specific agent.
What contributes to the addictive nature of certain drugs?
- They produce euphoria by acting in the reward pathways in the brain.
- Repeated use results in the adaptation of circuits in the central nervous system (CNS).
- Discontinuation leads to withdrawal symptoms.
- Tolerance develops, requiring increased doses to produce the same effects
How do drugs affect the brain’s reward pathways?
- Drugs “kidnap” reward circuits in the brain.
- They hit the circuits much harder than natural reinforcers.
- Drug abusers’ circuits have been overactivated.
Why do we need reward pathways in the brain?
- They reinforce behavior for repetition.
- They are involved in activities such as food consumption, drinking water, procreation, and child nurturing/rearing, which are essential for survival.
- These activities are called “natural reinforcers.”
Which neurotransmitters are involved in the brain’s reward pathways?
- Dopamine: reward and motor control.
- Serotonin: memory, sleep, and cognition.
What role does the VTA play in addiction?
The VTA (ventral tegmental area) releases dopamine, a neurotransmitter associated with reward and motivation.
What is salience in the context of addiction?
Salience is a cognitive process that confers a desire to a rewarding stimulus. It is hijacked by drugs, leading to a strong desire for drug consumption.
What are the components of top-down control in a non-addictive brain?
- The components include:
- Salience, which confers desire to a rewarding stimulus.
- Control and self-regulation by the prefrontal cortex (PFC), which tells you not to take the drugs.
- Weak memories of taking the drug.
How does the addictive brain differ from the non-addictive brain in terms of drug consumption drive, memory, and control?
In the addictive brain, there is a strong drive to take the drug, strong memories of pleasurable effects of the drug, and weakened control in the PFC. These factors contribute to a bigger drive to take the drug.
Do drugs of addiction share a common pathway?
- Dopamine is released from the ventral tegmental area (VTA).
- Dopamine is then released onto the nucleus accumbens.
- The control of dopamine neurons is regulated by GABA neurons, which are inhibited by opiates.
What is physical dependence on drugs?
- Results from adaptation, involving the resetting of homeostatic mechanisms in response to repeated drug use
- Characterized by withdrawal syndrome, which occurs upon the abrupt termination of drug use. The signs and symptoms of withdrawal are characteristic of the drug category.
What is psychological dependence on drugs?
- Involves a motivational component, characterized by craving for the drug.
- Unlike physical dependence, psychological dependence is not always associated with physical symptoms. Some drugs, like cocaine, can lead to long-lasting psychological dependence even in the absence of physical dependence.
What is tolerance to drugs?
Reduction in the response to a drug after repeated administrations, necessitating increased concentrations of the drug to achieve the same effect.
What is innate tolerance to drugs?
Innate tolerance is genetically determined sensitivity to a drug, which may occur after the first dose.
What is cross tolerance to drugs?
- Tolerance to one drug leads to a reduced response to another drug, even if it has not been taken before.
- For example, tolerance to cocaine can result in reduced response to amphetamines, and tolerance to benzodiazepines can reduce the effects of barbiturates.
What is the role of arrestin in the regulation of opiate receptors?
- Opiate receptors (GPCRs) undergo a process involving receptor activation, phosphorylation, and binding of arrestin.
- Arrestin binding prevents receptors from signaling, and the receptors can be endocytosed. Eventually, the receptors are recycled and return to the cell membrane.
- In the context of heroin addiction, this process might hypothetically result in a smaller number of receptors due to endocytosis, creating a scaling mechanism where more drug is needed, but fewer receptors are available.
What are the dangers associated with resuming drug use after a period of abstinence in terms of tolerance mechanisms?
Resuming drug use after a period of abstinence can lead to dangerous outcomes due to the disappearance of tolerance mechanisms.
What is pharmacodynamic tolerance?
Changes in receptors, so if one takes the same dose of a drug as before, it can result in a fatal overdose.
What is pharmacokinetic tolerance?
- Changes in drug metabolism enzymes.
- During abstinence, the levels of these enzymes may decrease. If one binges on the drug again, it can lead to dangerous concentrations of the drug in the bloodstream
