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PCL470 > Opioid Analgesics and Antagonists > Flashcards

Opioid Analgesics and Antagonists Flashcards

1
Q

Opioids

A

all naturally occuring and synthetic substances which bind to opioid receptors in the brain and periphery

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2
Q

opiates

A

drugs derived from opium

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3
Q

opium

A

natural product from poppy plant
greeks and romans used it to produce sleep
chewed or smoked

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4
Q

analgesia

A

absence of the sense of pain without loss of consciousness

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5
Q

spinal analgesia

A
  • suppression of pain by analgesic drugs into the space around the spinal cord
  • opiates interfere with transmission of pain messages between neurons and prevent them from reaching the brain
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6
Q

supraspinal analgesia

A
  • suppression of pain by drugs in the brain itself
  • allows a person to know they are experiencing a stimuli that would otherwise be painful
  • reduced perception of pain
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7
Q

opioid cellular actions

A

MOR at presynaptic terminal
- stimulated by opioid
- leads to decrease in calcium channels needed to use NT vesicles
- this results in less fusion
- this leads to less firing

MOR at post synaptic neuron
- stimulated by opioids
- increase in K+ channels
- hyperpolarization
- need more to transmit signal
- higher threshold to fire

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8
Q

Mu opioid receptors

A
  • located in all pain control areas of the brain and spinal cord (pariaqueductal gray in midbrain, spinal trigeminal nucleus, caudate nucleus, thalamic nucleus)
  • located in respiratory control centres and nucleus accumbens

functions
- analgesia (supraspinal and spinal)
- sedation
- inhibition of respiration
- slow GI
modulation of hormone and NT release

respond to
- exogenous opioid drugs
- endogenous opioids: endorphins > enkephalins > dynorphins

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9
Q

Kappa opioid receptors

A

located in
- basal ganglia
- nucleus accumbens
- VTA
- cortex
- hypothalamus
- periiaqueductal grey
- spinal cord

function
- modest analgesia, dysphoria, feelings of depersonalization, disorientation, pupil constriction, mild respiratory depression

responds to
- mixed agonist-antagonist (pentacozine and endogenous dynorphin): dynorphin&raquo_space; endorphins and enkephalins
- mixed ag-ant has affinity for two or more types of opioid receptors and blocks opioid effects on one receptor type while producing opioid effects on a second receptor type

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10
Q

Salvinorin A

A
  • pure kappa agonist
  • binds only to kaappa opioid receptor
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11
Q

delta opioid receptor

A

found in
-all pain control areas of the brain and spinal cord (pariaqueductal gray in midbrain, spinal trigeminal nucleus, caudate nucleus, thalamic nucleus)
- nucleus accumbens and limbic system

functions
- analgesia (supraspinal and spinal)
- modulation of hormone and NT release

respond to:
- exogenous etorphine
- endogenous enkephanils > endorphins and dynorphins

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12
Q

Types of pain neurons

A

nociceptors - general term for neurons that detect noxious stimuli and carry pain information from skin and muscle to the spinal cord

  1. mechanoreceptors
    - respond to pressure
  2. capsaicin receptors
    - respond to extreme heat, acid, and inflammation
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13
Q

How does the brain interpret pain and send moderating pain signals

A
  • nociceptor neuron releases substance P onto receiving neuron that projects up spinal cord
  • inhibitory neurons travel from the brain to the site of entry of nociceptors - act as INTERNEURONS
  • when stimulated they release endorphins that bind to the nociceptor neuron to inhibit pain (substance P or any other NT carrying pain information)
  • the interneuron can also be stimulated by exogenous opioids
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14
Q

3 ways opioids inhibit pain signals

A
  1. inhibiting Ca++ influx into presynaptic nociceptor neuron releasing substance P –> prevents substance P from being released because Ca++ is needed for NT releases
  2. hyperpolarizing post synaptic neuron by enhancing K+ outflow of neuron –> makes it more difficult to stimulate –> more difficult to send pain info
  3. modearte central perception of pain –> pain is less aversice when perceived
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15
Q

Endogenous opioid agonists

A

endogenous opiate peptides:
enkephalins
endorphins
endomorphins
dynorphin

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16
Q

Endorphin as an analgesic

A
  • endogenous opioid peptide
  • beta endorphin –> pain
  • derived from POMC (pre pro hormone)
  • produced by pituitary gland and the hypothalamus and releasd into blood stream from pituitary and into spinal cord and brain from hypothalamus
  • highest affinity for mu receptors
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17
Q

morphine/codeine

A
  • natural
  • derived from opium
  • codeine much less potent as analgesic
  • same chemical structure as morphine except one carbon and two hydrogen atoms removed
  • most analgesic effects are from metabolism to morphine
18
Q

heroin

A
  • natural
  • changed chemical structure makes it much faster acting than morphine because it is more fat soluble and easier to transport across membrane of the brain –> more addiction potential
19
Q

methadone

A
  • natural
  • more potent than morphine but less sedation
  • slow metabolism and very high lipid solubility –> longer lasting than morphine based drugs
  • milder withdrawal because of prolonged effects
  • cannot be injected
  • used as substitute for heroin and other narcotics as treatment
20
Q

dihydrocodeine

A

synthetic form of codeine

21
Q

fentanyl

A
  • synthetic
  • 80x more potent than morphine
  • remifentanyl is ultra short acting so it is safer due to less risk of respiratory depression
  • active sub 100ug so it is hard to measure
22
Q

hydromorphone –> hydrocodone metabolite

A
  • hydrocodone is the most used opioid
  • both analgesics and antitussive effects
  • bind to mu opioid receptor
23
Q

meperidine

A
  • synthetic
  • short acting
  • weak agonist
  • muscarinic and mu opioid effects
24
Q

oxycodone/oxycontin

A

oxycontin is the lost acting form, every 12 hours

25
Q

pentazocine

A
  • mixed agonist antagonist
  • acts as full agonist receptor at kappa and antagonist at mu
  • less addiction potential because stimulation of mu is risk in abuve
26
Q

buprenorphine

A
  • synthetic
  • partial agonist at mu
  • antagnost at kappa and delta
  • equal affinity but less intrinsic activity than endogenous opiates
  • less addiction potential
27
Q

opiate antagonists

A
  • naloxone: opiate OD
  • nalmefene: opiate OD
  • naltrexone: alcoholism
28
Q

effects of opiate administration

A
  • brain stem: change automatic body functions, suppress breathing
  • limbic system: emotions and feelings of pleasure
  • spinal cord: block pain messages

hypothermia
hypotension
peripheral vasodilation
miosis - pupillary constriction
drying of secretions
constipation
respiratory depression

29
Q

effects of opiate administration

A
  • dangerous if alcohol or depressant drugs co present
  • decrease in sex drive
  • sedation and anxiolytic effects, relation
30
Q

opiates and the reward system

A
  • opioids inhibit GABA which allows for dopaminergic neurons in the VTA and nAcc to release more DA
  • increass activity in the reward system
31
Q

physical dependence vs psychological dependence

A

physical: physilogical state of adaptation in which the body’s physiology requires teh drug to work normally, withadrwal symptoms emerge in abstinence

psychological: subjective sense of needing or craving positive effects or to avoid negative effects associated with abstinence

32
Q

Is tolerance and dependence with opioids an issue in pain control and recreational drug use?

A
  • less of an issue if for pain
  • someone who uses opioids recreationally for a long time will become very tolerant
  • 60mg of morphine are required for respratory depression in non tolerant people and 2000mg in people who are maximally tolerant (have SUD)
33
Q

what are the reasons for opiate withdrawal?

A
  1. opiates inhibit NT release –> body compensates for this by increasing number of receptors –> when opiate is taken away the abundance of receptors leads to a hyperactive state
  2. when opiates block enzyme –> the body compensates by increases enzyme production –> opiate removed –> rebound increase in enzyme and its product
34
Q

what are the symptoms of opiate withdrawal?

A
  • serious drug craving
  • dysphoria
  • yawning and panting
  • perspiration, runny nose, teary eyes
  • pupil dilation
  • fever and chills
  • tremors and muscle twitches
  • severe aching and painful sensation
  • loss of appetite
  • diarrhea
35
Q

tail flick test

A
  • rat placed on box with a light source coming from it that is hot
  • when it is too hot they flick their tail away
  • can give analgesic and test how long they last
  • if they don’t remove their tail it is evidence of analgesia
36
Q

hot plate test

A

mice placed on hot plate
when it is too hot they lick their paws to cool them down

37
Q

conditioned place preference method

A
  • animals injected w drug of abuse on one side in one session and vehicle on other side in another session
  • on test day animals are allowed to explore the boxes
  • animals tend to spend more time on the side that was paired with the rewarding drug
38
Q

locomotor activity test

A

measuring the horizontal and vertical movement of mice when given drug vs WT

39
Q

tail suspension and forced swim test

A
  • animal hung by tail or forced to swim in water
  • animal will struggle more and swim more when given antidepressant
  • does not necessarily mean that the mouse is depressed if it doesn’t swim
40
Q

morris water maze

A

model for alzheimers
- tests spatial memory
- mouse has to swim in a pool with hidden platform
- after training session they ahve to locate the platform
- mouse with high tau protein will swim around more and wont remember locaiton
- mouse with cleared tau will remember where to go

PCL470 (14 decks)

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