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C PSYC 462 > Opioids > Flashcards

Opioids Flashcards

1
Q

What are opioid drugs?

A

narcotic analgesics (reducing pain without loss of consciousness)

Some Molecules: morphine, codeine, thepaine, narcotine)

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2
Q

What is morphine the main active ingredient in?

A

Main active ingredient in opium (isolated in 1800s)

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3
Q

What is opium?

A

Opium is poppy plant extract. Used in 1700s in wine stuff (laudanum + paregoric)

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4
Q

How is heroin made?

A

Semi-synthetic: increases bioavailability. Adding 2 acetyl groups to morphine making it more lipid solute: reach brain faster, more potent, but once its in brain, the molecule that acts on things is morphine.

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5
Q

Where do opioid drugs bind?

A

Receptors in brain (using radioligand binding assays) and in the gut.

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6
Q

What are the different opioid receptor subtypes?

A 
All metabotropic
Mu
delta
kappa
NoP-R
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7
Q

Describe Mu.

A

High affinity for morphine (area shows effects)

  • medial thalamus, PAG, raphe, locus coeruleus, spinal chord = ANALGESIA
  • brainstem= CARDIOVASCULAR, RESPIRATOR CONTROL, COUGH, NAUSEAU/VOMIT
  • Thalamus, striatum= SEMSORIMOTOR INTEGRATION
  • NAc FEEDING, POS REINFORCEMENT
  • thought to mediate pleasureable aspects of fatty foods and orgasms
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8
Q

Describe the delta receptor?

A

Forebrain structures. overlap with mu receptors.

  • olfaction, motor integration, reinforcement, cognitive function
  • modulation of analgesia because of overlap with mu.
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9
Q

Describe the kappa receptor

A

striatum, amgydala, hypothalamus

  • makes you feel BAD
  • pain perception, gut motility and dysphoria
  • identified by binding ketocyclazocine which is an opioid that produces halluciations and dysphoria. bad cousin of mu
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10
Q

Describe the Nociceptin/Orphanin FQ receptors.

A

Wide distribution (cortex, limbic, thalamus, raphe, spinal chord)

  • does not bind opiod drugs
  • lowers pain threshold, opposite to mu and delta
  • feeding, learning motor function and neuroendocrine regulation
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11
Q

What are endogenous opiods?

A

Found out that PEPTIDE TRANSMITTERS bind to opioid receptors in 1970s
- Enkephalin (in the brain)

Multiple peptides discovered = ENDORPHINS (endogenous morphine)

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12
Q

How are endogenous opioids made?

A

In cell body, pro peptides are made with active parts within them that are cut up in the terminal into peptide transmitters. The propeptides have endogenous opiates and other transmitters in them.

Different variations exist. Co localized with other neurotransmitters in nerve terminals.

POMC: b-endorphine
PROENKEPHALIN: met ENK and leu-ENK
Dynorphin A and B

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13
Q

What are the preferences of endogenous opioids?

A

Not selective, but preferential.

Mu: endorphins and a bit of endomorphins (no propeptide for endomorphins yet)

Delta: enkephalins and endorphins

kappa: dynorphins

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14
Q

How do opioids inhibit neural activity?

A
  1. Postsynaptic inhibition: G protein that opens K + channels to hyperpolarize
  2. Axoaxonic inhibition heteroreceptors: activate G proteins to close Ca2+ channels reducing transmitter release (but net effect CAN be disinhibitory depending on circuitry)
  3. Presynaptic autoreceptors
    - reduce release of neurotransmitter.

All inhibit adenylyl cyclase c-AMP

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15
Q

What are some natural narcotics?

A

Opium

  • Codeine
  • Morphine
  • thebaine
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16
Q

What are some semisynthetic narcotics?

A

FROM MORPHINE
- heroin and hydromorphone (dilaudid)

FROM THEBAINE

  • oxycodone (percodan)
  • Etorphine

Many activate Mu receptors.

17
Q

What are some totally synthetic narcotics?

A 
Pentazocine (Talwin) 
Meperdine (Demerol) 
Fentanyl (Sublimaze) 
Methadone -opioid replacement strategy (Dolophine) 
LAAm 
Propoxyphene (Darvon)
18
Q

What are some endogenous opiods?

A

Enkephalins, Endorphins, Dynorphins, Endomorphins

19
Q

What is an example of a partial agonist for opiod receptors?

A

Buprenorphine: less potent than morhpine but less respiratory depression and dependence.

20
Q

What are some antagonists of opioids?

A

Naloxone and Naltrexone: no efficacy. Prevent or reverse the effect of opioids.

21
Q

What are the 3 ways that opiods can inhibit pain signals within the spinal cord?

A

Prevent signal transduciton.

  1. Directly activate opiod receptors in neurons in spinal cells. Inhibitory interneurons.
  2. Descending pathway to effect neural activity, Opiates in the brain cause it to send an inhibitory signal to inhibiti pain projections.
  3. Descending pathway to inhibit excitatory interneuron that synapse on pain projection cells

The desce

22
Q

How do descending pain signals get activated?

A

Opiods activate 2 descending pain inhibiting pathways from PAG.

  • rich with opiod peptides and receptors.
  • stimulation makes analgesia (stopped with antagonists) this is shown in rats that self administer.
  • projections from PAG DISINHIBIT raphe (5ht) and locus coruleus (NE) descending projections that suppress pain signals in spinal cord.
23
Q

What does opioid activity in supraspinal locations do?

A

In areas like sensory, limbic, or hypothalamic areas, it mediates emotional, autonomic, and neuroendocrine components of pain. So a combo of spinal and supra spinal can reduce conduciton and blunt emotional response.

24
Q

How does acupuncture decrease pain

A

Activate endogenous opioid system:
PROVEN
1) given nalaxone reduces effect
2) FMRI showed activity in PAG

25
Q

What are the effects of opioids at low and high doese? Therapeutic vs recreational?

A

Therapeutic: intramuscuarly or orally, slower, no euphoria
REcreationally: IV, inhalation, snorting, subcutaneous) more rapid

Low dose: pain relief, constricted pupils, drowsiness, no concentration, dreamy sleep
High dose: euphoria!

Highest dose: sedative effects lead to unconciousness and death
- suppress brainstem respiratory center

26
Q

What are the aversive effects of opioids?

A

Not everyone reacts the same way.

dysphoria, restlessness, anxiety, nausea.

  • reduces gastro motility (constipation is a common side effect, reducing smooth muscle contraction)
  • used to treat diarrhea (and the dehydration that comes with it) for things like stomach parasites tho.
  • if you give a receptor antagonist that doesn’t cross the BBB you can get the analgesic effects without the gastro effects.

IV administration risks
- infection, collapsed veins, liver damage, kidney damage, but compared to other drugs the toxic effects aren’t that bad (except for overdose)

-new studies show cognitive deficits, PFC functions, permeant changes.

27
Q

How are opioids reinforcing?

A

animals and humans readily self administer. (Mu receptor stimulation, kappa is bad)

Opiods activate mesolimbic dopamine path! (rewards)

  1. Mu activation in VTA inhibit GABA neurons, disinhibiting DA = more DA release in NAc
  2. Kappa activation on DA terminals in NAc reduces DA release with presynaptic inhibition. (maybe its why they’re so aversive?)
28
Q

Describe opioid tolerance.

A

Tolerance develops at different rates.

  • analgesia/pleasure is fast
  • constibuation, pupillary dilation and respiratory depression is slow

Tolerance is mostly pharmacodynamic (changes at cellular level to compensate)

Cross tolerance occurs (morphine - fentanyl)

29
Q

Describe opioid withdrawal.

A

opioids depress CNS function, withdrawl activates it so much.

  • unpleasant, not deadly. (pain, dysphoria)
  • worst on 2nd or 3rd day, done in a week

Severity depends on dype of drug (morphine, heroin is severe, methadone and buprenophine is less sever)

Precipitated by opioid antagonists (Naloxone)

30
Q

How do opioid antagonists precipitate withdrawal symptoms

A

Systemically or certain nuclei.
Systemically: quick and intense withdrawl.

Distinct nuclei: show that different regios do different things.

LOcus or PAG: opioid antagonists trigger physical symptoms of withdrawal (so if you reduce locus activity you reduce the severity of the withdrawal, or give NE also reduce)

Other regions like NAc and amygdala are in charge of emotionally aversive effects. If you administer antagonists, you get emotional effects.

If you re-administer, (with same or different drug, remember cross dependent) you reduce or eliminate withdrawal symptoms.

31
Q

How does tolerance withdrawal operate at a single cell level?

A

Morphine inhibits syntehsis of cAMP, but with repeated treatment cells adapt to produce more camp, but if you remove morphine or add naloxone you get increased camp levels.

IN locus coeruleus, morphine reduces firing rate, but adapt over time. If you give naltrexone or withdrawl, you get increase locus firing above normal levels.

32
Q

How do you initially treat opiod addiction.

A

Detoxification, can be assisted with drugs. Reducing locus coeruleus activity with alpha 2 adrenergic agonists (clonidine) can make NE more normal, but doesn’t relieve all symptoms and has other side effects.

33
Q

what are maintenance and replacement treatments for opioid addiciton?

A

Methadone: Opioid agonist, less potent when given orally (high if injected so you have to watch ppl), prevents severe withdrawal and reduces cravings. cross tolerance develops so euphoric effect of heroin are reduced, reducing liklihood of relapse.

Opioid antagonist: naltrexone (longer lasting than naloxine, orally active)

  • for motivated ppl
  • must take it every day. doesn’t stop craving, only stops effects.

C PSYC 462 (19 decks)

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