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Neuropharmacology > Chapter 11: The Opioids > Flashcards

Chapter 11: The Opioids Flashcards

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1
Q

Opioids

A

Class: narcotic analgesics

*reduce pain without producing unconsciousness but do produce sense of relaxation and sleep

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2
Q

Opiate narcotics are derived from […]

A

Opiate narcotics are derived from poppy plant

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3
Q

Natural Narcotics (Opiates)

A

Opium
Morphine
Codeine- less analgesic effects and fewer side effect than morphine
Thebaine

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4
Q

Opioids consist of:

A

Semisynthetic narcotics
Synthetic narcotics
Endogenous neuropeptides

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5
Q

Semisynthetic narcotics

A 
Derived from morphine:
         - Heroin
         - Hydromorphone (Dilaudid)
Derived from thebaine:
         - Oxycodone (Percodon)
         - Buprenorphine (Buprenex)
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6
Q

Synthetic narcotics

A 
Pentazocine (Talwain)
Meperdine (Demerol)
Fentanyl (Sublimaze)
Methadone (Dolophine)
LAAM
Propoxyphene
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7
Q

Endogenous Neuropeptides

A 
Enkephalins
Endorphins
Dynorphins
Endomorphins
Nociceptin/ orphanin FQ
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8
Q

Partial Opioid Agonists

A

Pentazocine (Tolwin)
Narbuphine (Nubain)
Buphrenone (Beprenex)

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9
Q

Pure antagonists

A

Naloxene (Narcan)

Nalorphine

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10
Q

Endogenous opioids are derived from […]

A

Endogenous opioids are derived from pro-peptides

  • POMC
  • Proenkephalin
  • Prodynorphin
  • Pronociceptin/ophanin FQ
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11
Q

POMC

A

Beta- endorphins (B-END)
Mu and delta receptors

  • found in pituitary gland and releases variety of hormones
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12
Q

Proenkephalin

A

Met- and leu-enkephalin (ENK)
Delta receptors
Inhibited by peptidases RB-101, RB-120, RB-3007

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13
Q

Prodynorphin

A
  • a- and B-neoendorphin
  • dynorphin (DYN) A and B
  • kappa receptors
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14
Q

Pronociceptin/ ophanin FQ

A

NOR receptors

Phenylalanine and glutamine

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15
Q

BU08028

A

Dual MOR-NOP-R agonist

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16
Q

There are 4 opioid receptors

A

High opioid affinity (highly selective)

  • Classical subtypes: mu, delta, kappa
  • NOR

*biased agonism

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17
Q

Mu receptors

A
  • high affinity for morphine
  • medial thalamus, peri aqueduct all gray (PAG), median raphe, and clusters in spinal cord
  • feeding and positive reinforcement
  • cardiovascular and respiratory depression
  • nausea and vomiting
  • sensorimotor integration
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18
Q

Delta receptors

A
  • forebrain: neocortex, striatum, olfactory areas, substantia nigra, and nucleus accumbens
  • olfaction, motor integration, reinforcement, and cognitive function
  • similar to MOR
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19
Q

kappa receptors

A
  • high-affinity binding to ketcyclazocine
  • striatum, amygdala, hypothalamus, pituitary
  • pain perception, gut motility and dysphoria
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20
Q

NOR

A
  • cerebral cortex, amygdala, hippocampus, and hypothalamus

- analgesia, feeding, learning, motor function, and neuroendocrine regulation

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21
Q

Opioid receptors are […] receptors

A

Opioid receptors are GPCR receptors

  • inhibitory
  • increased gk- opens channels
  • decreased gca- closes channels
  • adenylyl cyclase- inhibits activity (longer term effects)
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22
Q

Opioid receptor isolation, transfection, receptor cleaning, and molecular sequence

A
  1. Specific nucleic acid sequence
  2. AA of protein can be identified
  3. Transfected cells used to study intracellular changes
  4. In situ hybridization: visualize cells that synthesize receptors
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23
Q

Neuropeptides reduce synaptic transmission

A

*inhibition of endogenous opioids

  1. Postsynaptic inhibition: open K+ channels
  2. Axoaxonic inhibition: close Ca2+ channels (usually GABAergic neurons)
  3. Presynaptic autoreceptors: reduce transmitter release
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24
Q

Inhibition of […] and […] is important because they are used to transmit pain signal

A

Inhibition of Glu and Substance P is important because they are used to transmit pain signal

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25
Biased Agonism
Receptor activated dictates which signal is activated
26
Opioids in CNS
Decreased body temp and blood pressure, pupils restricted, and increased blood CO2
27
Opioids in GI tract
Relief of diarrhea and dysentery acid
28
Opioids induce several behavioral effects
Analgesia: - most effective pain-reliever Changes in mood - euphoria (MOR, DOR) - dysphoria (KOR) Drowsiness - sleep
29
Opioid PNS effects
- pinpoint pupils - vomiting - cough suppression (codeine) - constipation
30
Death by opioid
- respiratory depression | - cardiac depression
31
Opioid overdose triad
Pinpoint pupil, unconsciousness, respiratory depression - treat using Narcan
32
Acutely MOR agonist are […] and […]
Acutely MOR agonist are analgesic and reinforcing - Analgesia - Reward
33
Analgesia
Spinal- release endorphins that inhibit activation of spinal projection neurons Supraspinal- above spinal cord
34
Reward
Increased DA release in NAcc - B- endorphins are similar - K-agonists: decreased DA
35
Analgesic properties of opioid are due to agonism of MOR located in brain and spinal cord
- Midbrain periaqueductal gray matter - Locus coeruleus - Raphe nuclei - Dorsal horn of spinal cord * anterolateral system- ascending pain information
36
Opioids regulate pain
1. In spinal cord by small inhibitory interneurons 2. Descending pathways originating in periaqueductal gray (PAG) 3. At higher brain sites (emotional and hormonal aspects)
37
MOR agonists directly […] neurons and have reward properties
MOR agonists directly activate mesolimbic DA neurons and have reward properties - ICSS - Self-administration - Microinjection studies
38
ICSS (intracranial self-stimulation)
opioids decreases the threshold current required for ICSS - morphine or selective mu- agonist and place preference
39
Median forebrain bundle
Bar press rewards
40
Self-administration
IV use gradually increases over time | - similar to pattern seen in humans
41
Microinjection studies
Intra-VTA microinjection increases firing rate and DA release from VTA Induces CPP and decreases threshold for ICSS
42
Opioids […], increases their firing rate, causing more DA release in N. Acc.
Opioids disinhibition VTA neurons, increases their firing rate, causing more DA release in N. Acc.
43
6-OHDA lesions […] self-administration, showing the rewarding properties of opioids also involve other, non-DA mechanisms
6-OHDA lesions reduce self-administration, showing the rewarding properties of opioids also involve other, non-DA mechanisms
44
Chronic opioid use produces increased craving, physical dependence and tolerance
- incentive sensitization - pharmacodynamic tolerance - withdrawal/ abstinence syndrome
45
Incentive sensitization
- increased invention salience - craving; “wanting” (Craving undergoes sensitization)
46
Pharmacodynamic Tolerance
- also metabolic and behavioral tolerance | - cross-tolerance with other OR agonists
47
Withdrawal/ abstinence syndrome
Loss of inhibitory opioid action at all receptors as blood levels of drug decline *rebound hyperactivity
48
Cross- tolerance
Tolerance to one opioid drug—> other chemically related drugs also show reduced effectiveness
49
Detoxified
When abstinence signs end
50
Cross Dependence
Readministering any opioid will stop/ reduce withdrawal symptoms
51
Physical dependence occurs following long-term occupation of opioid Acute action: withdrawal symptoms
Analgesia: pain and irritability Respiratory depression: panting and yawning Euphoria: dysphoria and depression Relaxation and sleep: restlessness and insomnia Tranquilization: fearfulness and hostility Decreased blood pressure: increased blood pressure Constipation: Diarrhea Pupil constriction: pupil dilation Hypothermia: hyperthermia Drying of secretions: tearing, runny nose Reduced sex drive: spontaneous ejaculation Flushed and warm skin: chilliness and “gooseflesh”
52
Neuroadaptations underlie the transition to addiction
Nucleus accumbens Locus Coeruleus Periaqueductal Gray
53
Abrupt removal of opioid in tolerant/ dependent animals leads to a withdrawal syndrome
Normal Begin morphine treatment: acute Tolerance and dependence Withdraw morphine (abstinence) Withdrawal and normal
54
Neuroadaptations following chronic opioid use are related to […] and […]
Neuroadaptations following chronic opioid use are related to tolerance and withdrawal
55
Tolerance
- MOR desensitization: uncoupling of MOR and G protein occurs rapidly (min) - MOR down-regulation and internalization occur more slowly (1-3 days)
56
Withdrawal (WD)
Intracerebral injection of naloxone to - LC/ PAG - physiological symptoms of WD - N. Acc.- aversive qualities of WD (depression, dysphoria)
57
Neuroadaptations following chronic opioid use are related to tolerance and withdrawal
Acute Chronic Induce WD
58
Acute Use
- activate MOR in LC | - Hyperpolarization; less AP firing
59
Chronic Use
- LC neurons gradually increase AP firing - cAMP/ PKA activity gradually increases - chronic morphine doesn’t change number of receptors (tolerance)
60
Induce WD
- administer naloxone to dependent animal - LC neurons are over-excited - cAMP/ PKA over-activated
61
Neurobiology of Opioid Addiction
Increased cAMP PMOR Increased LC Increased DA release POST NEUROADAPTATION; ``` MOR desensitization MOR internalization Tolerance LC hyperactivity Anti-reward ``` Positive feedback loop: LC to Central Nucleus of Amygdala and back
62
Innovative pain control
Dual- inhibition of peptidases Dual MOR/NOR agonists
63
Dual-inhibition of peptidases
- inhibition of both ENK degrading enzymes - fewer side-effects - low abuse potential
64
Dual MOR/ NOR agonists
- potent, effective analgesia - no respiratory depression or cardiac side effects - no physical dependence, low abuse potential
65
2 components of pain
Early- immediate sensory component; signals onset of noxious stimuli and precise location - Ad fibers - Spinothalamic tract —> posteroventrolateral (PVL) nucleus of thalamus —> primary and secondary somatosensory cortex Late- strong emotional component (unpleasantness) - C fibers - Thalamus —> hypothalamus, amygdala, anterior cingulate cortex
66
Environmental cues have role in tolerance, drug abuse, and relapse
- Triggers- cues that act as secondary messengers | - Learning is critical in opioid use disorder
67
Detoxification is assisted using […] and […]
Detoxification is assisted using methadone and clonidine - methadone maintenance program
68
Buphrenorphine (Buprenex) maintenance
Opioid partial agonist used to similarly to methadone - High affinity, low Africans MOR - Antagonist at KOR
69
Naltrexone (Trexan)
Commonly used narcotic antagonist

Neuropharmacology (15 decks)

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