Final review Flashcards
*Broadly describe some of the neuropsychological consequences of chronic cannabis use (Q30)
- Tolerance: typically pharmacodynamic (involving a combo of desensitization and down-regulation of CB1 receptors), evidence that desensitization can be reversed
- Dependence: 10% of cannabis users become dependent
- Withdrawal: absence of withdrawal symptoms in studies may have been due to the long elimination half-life of THC; involves lower dopamine VTA firing and increased CRF and cortisol release
What % of cannabis users become dependent? (Q30)
10%
Describe cannabinoid tolerance (Q30)
- Typically pharmacodynamic; involves a combination of desensitization and down-regulation of CB1 receptors
- There is evidence that it can be reversed
What are some withdrawal symptoms of cannabinoid? (Q30)
- Irritability
- Increased anxiety
- Depressed mood
- Sleep disturbances
- Heightened aggressiveness
- Decreased appetite
In some studies, researchers reported a lack of cannabinoid withdrawal symptoms. Why? (Q30)
Might have been due to the long elimination half-life of THC
What does cannabis withdrawal involve? (Q30)
- Lower dopamine VTA firing
- Increased CRF and cortical release
*Identify five acute psychological effects associated with typical recreational doses of inhaled cannabis (Q27)
- Pain perception: reduced unpleasantness of pain, but intensity of pain remains the same
- Visual selective attention: increase in reaction times, decrease in accuracy, reduced binocular depth inversion
- Auditory effects: improved rhythm perception
- Memory: all aspects of memory impaired but especially working memory
- Euphoria: dependent on the THC content
Explain the role of cannabis in pain perception (Q27)
- Reduced unpleasantness of pain
- Intensity of pain remains the same
Explain the role of cannabis in visual selective attention (Q27)
- Increase in reaction times
- Decrease in accuracy
- Reduced binocular depth inversion
Explain the role of cannabis in audition (Q27)
- Improved rhythm perception
Explain the role of cannabis in memory (Q27)
- All aspects of memory impaired, but especially working memory
Explain the role of cannabis in euphoria (Q27)
- Dependent on the THC content
- May be related to pain perception effects
*Identify some of the behavioural and physiological atypicalities observed in both CB1 and CB2 knockout mice (Q29)
- CB1 knockout mice lack four characteristic THC-induced effects: reduced locomotion, hypothermia, catalepsy, hypoalgesia
- CB1 knockouts do not show extinction of fear conditioned responses to auditory cues
- CB2 knockout mice exhibit hyperalgesia
Describe CB1 knockout mice (Q29)
- CB1 knockout mice lack four characteristic THC-induced effects: reduced locomotion, hypothermia, catalepsy, hypoalgesia
- CB1 knockouts do not show extinction of fear conditioned responses to auditory cues
CB2 knockout mice exhibit what? (Q29)
Hyperalgesia
*Describe some of the unique features of endocannabinoid neurotransmission compared to other neurotransmitter systems (Q26)
- Too lipid soluble to be stored in vesicles because they would pass right through the vesicle membrane
- Instead of being stored in vesicles, they are made and released when needed
- Endocannabinoids are retrograde messengers at specific synapses in some brain regions (ie. hippocampus, cerebellum)
- After they are released, endocannabinoids are removed from the extracellular fluid by an uptake mechanism
- They can be metabolized by several different enzymes (ie. FAAH, MAGL)
What enzymes can metabolize endocannabinoids? (Q26)
- FAAH
- MAGL
Why can’t endocannabinoids be stored in vesicles? (Q26)
They are too lipid soluble and would pass right through the vesicle membrane
*Cannabis is becoming increasingly common in the treatment of some chronic pain disorders. Explain how the underlying neural circuitry for pain is modulated by the use of cannabis (Q28)
- CB1 receptor agonists directly decrease the firing rate of peripheral nociceptive neurons
- Spinal and thalamic neurons in the pain pathway are similarly affected by agonists
- Distinct central sites of anti-nociceptive action: PAG, RVM, A5 NE cells
What do CB1 receptor agonists do (pain + cannabis)? (Q28)
Directly decrease the firing rate of peripheral nociceptive neurons
What other neurons in the pain pathway are similarly affected by CB1 receptor agonists? (Q28)
Spinal and thalamic neurons
What are the distinct central sites of anti-nociceptive action? (Q28)
- PAG
- RVM
- A5 NE cells
*Provide an account of the mechanisms of action for the psychoactive effects of cocaine (Q1)
- Different routes of administration produce different effects due to the time course of distribution
- Crosses the BBB because it is lipophilic
- Quickly broken down by blood and liver enzymes
- Half-life is typically 0.5-1.5 hours
- High affinity for SERT > DAT > NAT
- Low affinity for voltage-gated Na+ channels
Why does cocaine cross the BBB? (Q1)
It is lipophilic
Cocaine is quickly broken down by what enzymes? (Q1)
Blood and liver enzymes
What is the half-life of cocaine? (Q1)
0.5-1.5 hours
Cocaine has a high affinity for what? (Q1)
SERT > DAT > NAT
Cocaine has a low affinity for what? (Q1)
Voltage-gated Na+ channels
*Provide an account of the mechanisms of action for the psychoactive effects of amphetamines (Q2)
- Half-lives range from 7-30 hours
- Metabolites mostly excreted in urine
- Amphetamines and methamphetamines are indirect agonists of the catecholaminergic systems
- At very high doses, amphetamines can act as MAO antagonists
- Reversal of DAT function is caused by phosphorylation through PKC
- Release of NE happens in both the brain and the sympathetic nervous system
What is the half-life range for amphetamines? (Q2)
7-30 hours
Amphetamine metabolites are mostly excreted how? (Q2)
In urine
Amphetamines and methamphetamines are indirect agonists of what systems? (Q2)
Catecholaminergic systems
At very high doses, amphetamines can act as what? (Q2)
MAO antagonists
Reversal of DAT function is caused by what? (Q2)
Phosphorylation through PKC
*Explain why amphetamines and other psychostimulants are used in the treatment of attention deficit disorders (Q3)
- Low doses of amphetamines produce calming effects in more than half of ADHD sufferers
- Abnormal prefrontal cortex activity is restored to near normal
- α2A and DA1 receptors are most implicated
- Enhancing catecholaminergic activity in the PFC has been suggested to be a crucial component in ADHD, and psychostimulants are capable of stimulating the release of and blocking the reuptake of catecholamines
Low doses of amphetamines can produce what kind of effects in almost half of ADHD sufferers? (Q3)
Calming effects
Amphetamines can restore what brain activity to near normal in those with ADHD? (Q3)
Abnormal prefrontal cortex activity
What receptors are most implicated in amphetamine treatment for ADHD? (Q3)
α2A and DA1
*Provide an account of the mechanisms of action for the psychoactive effects of nicotine (Q4)
- Typical cigarette contains between 6-11mg but only about one third of it reaches the bloodstream
- Enters the lungs on particles of hydrocarbon mixtures
- Smoking is the fastest and most efficient was of getting nicotine into the brain
- Half life is ~2 hours
- 70-80% metabolized to cotinine by CYP2A6 in the liver
- Mainly activates nAChRs in the CNS, PNS, muscle junction
- High dose can lead to biphasic response
What is the half life of nicotine? (Q4)
~2 hours
High doses of nicotine can lead to what? (Q4)
Biphasic response
Nicotine mainly activates what and where? (Q4)
nAChRs in the CNS, PNS, muscle junction
70-80% of nicotine is metabolized how? (Q4)
To cotinine by CYP2A6 in the liver
What is the fastest and most efficient way to get nicotine to the brain? (Q4)
Smoking
How does nicotine enter the lungs? (Q4)
On particles of hydrocarbon mixtures