B. 25. natural opiates, opioid receptors

Question 1

list 3 endogenous opioid peptides

Answer 1

Enkephalin
Dynorphin
β- endorphin

Question 2

what is the function of endogenous opioid peptides? (β-endorphin)

Answer 2

• modulate transmission in many sites in the brain and spinal cord (interneuron activity)
• found in the adrenal medulla and neural plexus of the gut (enteric nervous system)

Question 3

what are the 3 opioid receptors?

Answer 3

µ (mu)
δ (delta)
ᴋ (kappa)

Question 4

what is the mechanism of the action of opioid receptors?

Answer 4

Gi-coupled
presynaptic (Ca²⁺ influx ↓)

µ–> also postsynaptic (K⁺ conductance ↑)

Question 5

what is the opioid peptide affinity of µ (mu) receptor?

Answer 5

endorphins >enkephalins>dynorphins

Question 6

what is the opioid peptide affinity of δ (delta) receptor?

Answer 6

enkephalins> endorphins, dynorphins

Question 7

what is the opioid peptide affinity of ᴋ (kappa) receptor?

Answer 7

dynorphins» endorphins, enkephalins

Question 8

what are the functions of µ (mu) receptor?

Answer 8

1. supraspinal and spinal analgesia
2. sedation
3. inhibition of respiration
4. GI motility ↓
5. modulator of hormone and neurotransmitter release

Question 9

what are the functions of δ (delta) receptor?

Answer 9

supraspinal and spinal analgesia

modulator of hormone and neurotransmitter release

Question 10

what are the functions of ᴋ (kappa) receptor?

Answer 10

supraspinal and spinal analgesia
psychomimetic effects
GI motility ↓

Question 11

what are the acute physiologic effects of opioids? (9)

Answer 11

1. analgesia (pain relief)
2. sedation (additive with other CNS depressants)
3. respiratory depression (desensitization of CO₂)
4. antitussive action (suppression of cough reflex)
5. nausea and vomiting (stimulation of chemoreceptors in the area postrema)
6. intestinal motility ↓–> constipation (dose-dependent effect)
7. smooth muscle contraction (urinary tract)
8. miosis (pupillary constriction)
9. histamine release, ADH release

Question 12

what are the chronic physiologic effects of opioids?

Answer 12

tolerance

dependence (physical and psychologic)

Question 13

name 2 natural opiates

Answer 13

Morphine

Codeine

Question 14

is morphine a strong or weak agonist?

Answer 14

strong

Question 15

is codeine a strong or weak agonist?

Answer 15

weak

Question 16

what are the uses of morphine?

Answer 16

analgesic (post operative pain, chronic pain syndromes, post MI)
anesthesia (sedation, relieve anxiety)
acute pulmonary edema

Question 17

what is the toxic effect of Morphine?

Answer 17

respiratory depression

*but tolerance develops if given gradually

Question 18

when should morphine be avoided?

Answer 18

1. head trauma–> morphine ↑ CO₂ and CP
2. obstructive lung disease
3. cor pulmonale
4. alcohol intoxication/ withdrawal
5. epilepsy
6. acute abdominal catastrophy

Question 19

how much morphine do we give for an MI or burn injury?

Answer 19

10-20mg SC or 1-2mg IV

Question 20

what is the pill form of morphine?

Answer 20

morphine-sulphate 10-100mg

*given for tumor pain

Question 21

what are the uses of Codeine?

Answer 21

antitussive (suppress coughing)

analgesic effect in combination with NSAID’s or acetaminophen