FINAL QUESTIONS 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
*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
*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
- Hypothalamic effects are mediated by TRPV1, which also mediates LTD in the hippocampus
- TRPV1 is involved in thermal and pain regulation
*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)
*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
*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
- Binds to membrane DA transporter and blocks the reuptake of the neurotransmitters
- 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
*Provide an account of the mechanisms of action for the psychoactive effects of amphetamines (Q2)
- 2 drug related actions: cause DA molecules to be released from inside vesicles at cytoplasm of nerve terminal and DA molecules transported outside of terminal by reversal of DAT
- Half-lives range from 7-30 hours
- Metabolites mostly excreted in urine
- Amphetamines and methamphetamines are indirect agonists of the catecholaminergic systems
- Releases catecholamine from nerve terminals
- 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
*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
- A single dose early in the day will benefit the child throughout the day because it is long-acting
- 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
*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 nicotinic acetylcholine receptor sites in the CNS, PNS, muscle junction
- High dose can lead to biphasic response
*Provide an account of the mechanisms of action for the psychoactive effects of caffeine (Q5)
- Absorbed by the gastrointestinal tract within 30-60 minutes after consumption
- Stimulates calcium release within cells
- Absorption begins in the stomach but takes place mainly in the small intestine
- Plasma half-life is about 4 hours
- Converted in the liver to multiple metabolites
- Mostly excreted through urine
*Broadly outline (or list) the neurophysiological components of anxiety and match each CNS component with a behavioural or physiological correlate (Q6)
- Lateral hypothalamus: sympathetic activation
- Dorsal motor nucleus of Vagus: parasympathetic activation
- Parabrachial nucleus: increased respiration
- VTA, LC, PPN: activation of DA, NE, and ACh
- Nucleus reticularis: increased reflexes
- Periaqueductal grey: cessation of behaviour
- Trigeminal and facial nuclei: mouth open and jaw movements
- Paraventricular nucleus of hypothalamus: ACTH release
*Several neurotransmitters are thought to contribute to the experience of anxiety. Identify the ones discussed in lecture and for each one provide a one sentence summary about its contribution (Q7)
- CRF: prepares the organism for increased stress and utilization of energy
- Norepinephrine: involved in arousal and response to threats/novel situations, also improves memory formation for emotional events
- GABA: the GABAa receptor complex comprises a chloride channel that, when opened following GABA binding, allows chloride to enter the cell, causing hyper polarization
- Serotonin: 5HT agonists tend to be anxiolytic
- Dopamine: involved in fear and avoidance behaviour
*Provide an account of how benzodiazepines function to treat anxiety (Q8)
- Differences in effect duration are largely dependent on method of biotransformation and depot binding
- Long-acting benzodiazepines can have half-lives of 60+ hours and/or have multi-step metabolism with bioactive metabolites
- Short-acting benzodiazepines are metabolized in a single step
- Benzodiazepines can have sedative-hypnotic and memory impairing effects
- Clinically useful for relief of worry and physiological signs of anxiety with little to no tolerance for anxiolytic effects
- They are advantageous because they have a high therapeutic index, lethal overdose is rare, no liver enzyme increases, and lower dependence/abuse
*List five treatment options available for major depression and for each one provide a one sentence summary about how that option is supposed to work (Q10)
- MAOI: increases the amount of NT available for release; involves many side effects, but has an immediate effect on DA, NE, and 5HT synapses; antidepressant effects are the result of receptor regulation over time
- Tricyclic antidepressants: non-selective monoamine reuptake inhibitors, inhibition of reuptake prolongs the duration of transmitter action at the synapse; antidepressant effects are likely due to long term regulation, also block ACh, histamine, and α2 NE receptors
- Second generation antidepressants: not more effective than MAOIs or tricyclics but have less side effects, 5HT is complex and some side effects come from SSRIs; requires compensatory changes in neurons that occur over time
- Third generation antidepressants: comprise of CRF receptor antagonists, ketamine, galanin, etc.; ketamine is a dissociative anesthetic that has been shown to produce a rapid reduction in symptoms; galantines involved in mood disorders, cognitive performance, sleep, stress responses, etc.
- Electroconvulsive shock therapy: very safe and effective, causes a brief seizure in the brian, one of the fastest ways to relieve symptoms
*There are five families of endogenous opioids (endorphins). For each, name either the family itself or the propeptide from which they are derived (Q12)
- Endorphins: derived from POMC
- Enkephalin: derived from proenkephalin
- Dynorphins: derived from prodynorphin
- Nociceptin/orphanin FQ: derived from pronociceptin/orphanin FQ
- endomorphin: unknown