Brainscape's Knowledge GenomeTM


Top Flashcards (Certified)
All Flashcards

Neuro-pharmacology > Opioid Receptors and Systems > Flashcards

Opioid Receptors and Systems Flashcards

1
Q

A great variety of opioids exist

A

natural and synthetic, owing to
their unsurpassed potency as
analgesics.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

Natural narcotics

A

Opium
morphine, codeine, thebaine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

semisynthetic narcotics

A

Heroin, Hydromorphone, oxycodone, etorphine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

totally synthetic narcotics

A

Pentazocine, meperidine, fentanyl, methadone, LAAM, Propoxyphene

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

endogenous opioids

A

endomorphines, enkaphalins, endorphins, dynorphins, Nociceptin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

Opioid Potency

A

Analgesic effects are difficult to
directly measure in lab based assays
* In animal and human trials ethics limit
the types of experimental pain that
can be applied
* Human trials can be highly
confounded by subjectivity of pain
measures

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

We know opioids are potent
modulators of

A

GI mobility

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

Investigators developed a GI based

A

assay to measure the potency of
opioids

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

Ex vivo preparation of the

A

guinea pig
ileum

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

Application of hydraulic pressure
stimulates the

A

ileum peristaltic reflex

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

Morphine reversibly

A

Inhibits the
ileum peristaltic reflex,

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

opioid antagonist naloxone
rapidly restores

A

inhibition of Ileum peristaltic reflex by morphine

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

Opioid receptor discovery

A

Candace Pert and Soloman Snyder
finally identified the receptor using
radiolabelled naloxone (opioid
antagonist) in 1973

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

Opioid binding was demonstrated to
be

A

reversible, saturable, and of high
affinity.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

Opioid receptor
binding and
potency

A

Opioid receptor binding
by the radioligand assay
was shown to correlate
with the potency of
opioids in the guinea pig
ileum bioassay

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

Opioid receptor distribution

A
  • High binding observed in the striatum,
    locus coeruleus, thalamus, raphe
    nuclei, and periaqueductal gray
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

Receptor subtypes Four main subtypes exist

A

δ (delta)
κ (kappa)
μ (mu)
Nociceptin

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

Opioid receptors are

A

e G-protein coupled (to
Gi)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

Putative receptors include

A

ε (EOR) and ζ
(ZOR) and previously σ

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

δ (delta) –

A

DOR / OP1

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

κ (kappa)

A

– KOR / OP2

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

μ (mu)

A

MOR / OP3

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

Nociceptin

A

NOP / OP4

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

Varied expression of opioid receptors in the rat brain suggest

A

subtype specific roles.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
where are Mu receptors located
Striatum, thalamus, olfactory areas, cortex, Raphe Nuclei, Locus Coeruleus
26
WHere are delta receptors located
striatum, olfactory areas, cortex
27
where are Kappa receptors located
Striatum, Cortex, Thalamus, Raphe nuclei, Locus coeruleus
28
μ-opioid receptor (MOR) High affinity for
morphine
29
μ-opioid receptor (MOR) High expression in
thalamus, periaqueductal gray, median raphe suggests roles in analgesia
30
μ-opioid receptor (MOR) Expression in nucleus accumbens suggests role in
reinforcement
31
μ-opioid receptor (MOR) Expression in brainstem suggests roles in
n respiratory depression, cough suppression, and vomit reflex
32
δ-opioid receptor (DOR) Similar expression to
μ but more restricted
33
δ-opioid receptor (DOR) Not sensitive to
morphine
34
δ-opioid receptor (DOR) Roles in
olfaction, motor integration, reinforcement, and analgesia
35
κ-opioid receptor (KOR) Distinct
expression pattern
36
κ-opioid receptor (KOR) High affinity for
ketocyclazocine
37
κ-opioid receptor (KOR) Expressed in
striatum and amygdala, also hypothalamus and pituitary
38
κ-opioid receptor (KOR)Regulation of
pain perception, gut motility, and dysphoria
39
κ-opioid receptor (KOR)Additional roles in
water balance, feeding, temperature control, neuroendocrine function
40
ketocyclazocine
Synthetic opioid that is hallucinogenic and induces dysphoria
41
Nociceptin receptor Expressed in
amygdala, hippocampus, hypothalamus, and spinal cord
42
Nociceptin receptor Roles in
anxiety, depression, appetite, and development of tolerance to μ-opioid agonists
43
Enkephalins
‘in brain’ Selective for δ-receptor * Two subtypes
44
* Dynorphins
– from Greek dynamis, meaning power * Selective for the κ-receptor * Four subtypes
45
Endorphins
contraction from endogenous morphine Selective for the μ-receptor * Five subtypes
46
Endomorphins
also a contraction from endogenous morphine Selective for the μ-receptor * Extremely high affinity * At least two subtypes * Gene or prepeptide not yet identified
47
Nociceptin
Selective for the nociceptin receptor * Anti-analgesic * Single species
48
Despite dramatic size differences, endogenous peptides show
structural similarity to opiates but are considerably more potent
49
Endogenous peptide genes and synthesis
Endorphins, enkephalins, and dynorphins are synthesized from pre-propeptide genes
50
* Endorphins are expressed from
POMC, which also gives rise to melanocyte stimulating hormones and adrenocorticotropic hormone
51
β-endorphin release POMC is highly expressed in the
pituitary – peptides for both adrenocorticotropic hormone (ACTH) and β-endorphin
52
ACTH is released in response to
hypothalamic corticotropin releasing hormone (CRH) and acts on the adrenal cortex to release glucocorticoid hormones
53
Co-release of β-endorphin from the pituitary provides a
a physiological link between stresses and pain signaling
54
Endogenous opioid signalling is
inhibitory – this can affect neurotransmitter release through a number of different ways.
55
Postsynaptic inhibition is a result of
Gi signalling to adenylate cyclase and Gβγ signalling to hyperpolarizing K + -channels (GIRK).
56
Axoaxonal inhibition can be elicited through
G i and cAMP signalling to inhibit voltage gated Ca2+ -channels
57
Endogenous opioid signalling is inhibitory – this can affect neurotransmitter release through a number of different ways Presynaptic autoreceptors to
inhibit neurotransmitter release.
58
Pain is unique among the senses as it can be induced by a range of factors
mechanical, chemical, electrical, thermal, and inflammatory stimuli all affect nociceptive neurons.
59
Opioids are involved in modulating
pain pathways at both the spinal level and at supraspinal sites.
60
Pain perception has two components
Early pain late pain
61
Early pain
– immediate sensory component signalling stimulus location to cause withdrawal or escape from stimulus
62
Late pain
signals a strong emotional component, the unpleasantness of pain sensation – prolongs sensation of pain to focus behaviours to limit further damage and aid recovery
63
arly and late pain are signalled through
distinct neuronal pathways.
64
Ascending pain pathways
Sensory neurons in the dorsal root ganglia transmit signals in the dorsal horn to ascending pathways.
65
Early pain is signalled through
A δ fibers (large, myelinated axons – fast transmission).
66
A δ fibers project to the
thalamus and somatosensory cortex to provide location information on pain.
67
Late pain is signalled through
C fibers (small, unmyelinated axons – slower transmission).
68
C fibers project to the
thalamus but also innervate the limbic system (hypothalamus, amygdala, and anterior cingulate cortex).
69
early pain (pain recognition) responses correlate with
somatosensory activation
70
Late pain (identification of unpleasantness of pain) correlates
with ACC activation
71
Both components of pain
bilaterally activate the secondary somatosensory complex.
72
Sites of opioid analgesia
Spinal sites Supraspinal sites
73
Opioid receptors are expressed at multiple steps of pain Spinal sites
Opioidergic neurons are involved in descending modulatory pathways (either acting directly on projection neurons or on excitatory interneurons)
74
Opioidergic interneurons release
endorphins to inhibit ascending projection neurons
75
Supraspinal sites
Opioids function in the limbic system, thalamus, and sensory areas to modulate emotional components of pain
76
Descending pain modulation pathways The most important descending pathways originate in the
periaqueductal gray (PAG) in the midbrain.
77
periaqueductal gray (PAG) neurons project to the
raphe nuclei where seratonergic projections descend to provide inhibitory input to pain afferents
78
Further projections from the PAG terminate in
the locus ceruleus – noradrenergic cells increase firing in response to pain and are inhibited by μ-receptor agonists
79
Sustained pain results in extensive activation of
endogenous opioid signalling in limbic structures.
80
PET scan measuring displacement of a radiolabelled ligand for the μ -receptor ([11C]carfentanil) by endogenous opioids. Since the endogenous and exogenous ligand compete for
r the same site decreased signal from the PET ligand is proportional to increased release of endogenous opiates.
81
Opioid peptide effects on pain sensation In PET displacement studies, sensory pain scores correlated negatively with
opioid release in the nucleus accumbens, amygdala, and thalamus
82
Affective pain scores correlated negatively with
opioid release in the anterior cingulate cortex, thalamus, and nucleus accumbens

Neuro-pharmacology (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2025 Bold Learning Solutions. Terms and Conditions