Opioids

Question 1

What are the main opioid receptors

Answer 1

• μ = Mu (MOPr)
• δ = delta (DOPr)
• k = kappa (KOPr)
• ORL1 = Nociception receptor (NOPr)

Question 2

What is the behavioural responses of the Mu receptor

Answer 2

• Analgesia
• Euphoria
• Respiratory depression
• Constipation

Question 3

What is the behavioural responses of the Delta receptor

Answer 3

• Analgesia
• Antidepressant
• Proconvulsant

Question 4

What is the behavioural responses of the Kappa receptor

Answer 4

• Analgesia
• Dysphoria
• Hallucinations
• Diuresis

Question 5

Opioid receptora are G-protein coupled receptors, how do they function?

Answer 5

• Activation of inwardly rectifying potassium channel

* Inhibition of voltage operated calcium channels (N, P, Q and R) – not L-Type

Question 6

Functional consequences of opioid receptor activation

Answer 6

Inhibits neuronal firing by increased potassium conductance causing hyperpolarization

Inhibits transmitter release as there is decreased calcium entry

This causes Disinhibition - removal of an inhibitory influence causes excitation of descending inhibitory projections from the PAG to the spinal cord

Question 7

Sites of action of opioids to suppress pain

Answer 7

1. Peripheral sensory nerves – decrease firing of sensor nerves in the periphery by opening potassium channels.
2. Spinal cord - pre and postsynaptic actions to decrease flow of sensory information
3. Supraspinal sites (e.g. PAG) - to activate descending inhibitory projections to the spinal cord)

Question 8

Give some examples of opioid drugs

Answer 8

• Morphine – the gold standard
• Heroin (Diamorphine)
• Codeine – weaker analgesic
• Oxycodone – used in oral slow release tablets
• Methadone – long acting
• Buprenorphine mu partial agonist
• Tramadol - weak m agonist/noradrenaline re-uptake inhibitor

Question 9

Therapuetic effects of opioids

Answer 9

Relief of pain: 
o	Acute 
o	Chronic e.g. cancer, neuralgias
o	During surgery
o	Post operative analgesia

Treatment of severe diahorrea

Cough suppression

Question 10

Describe how Opiod induced euphoria works

Answer 10

• Disinhibition in the Ventral Tegmental Area (VTA)

* Enhances dopamine release in the nucleus accumbens

Question 11

What are used to treat opioid overdose

Answer 11

Naloxone and Naltrexone

Question 12

How do Naloxone and Naltrexone function

Answer 12

mu, kappa, delta antagoinsist

Question 13

What is in Co-codamol

Answer 13

codeine and paracetamol

Question 14

What is in Co-codaprin

Answer 14

codeine and asprin

Question 15

What is in Co-proxamol

Answer 15

dextropoxyphene and paracetamol

Question 16

Give some examples of non-opiod drugs used to treat pain

Answer 16

Carbamazepine (anti-epileptic agent)

Gabapentin/pregabalin (anti-epileptic agent)

Antidepressants (amitriptyline)