Session 11 - Receptor regulation

Question 1

What do the activation of u-opioid receptors do physiologically?

Answer 1

• Analgesia
• Sedation
• Euphoria

Question 2

What is the underlying mechanism of opioid dependence?

Answer 2

-Repeated use of an opioid causes mu receptors to become upregulated as tachyphalaxis occurs-> the receptors become insensitive to the opioid so more receptors are required to be activated to produce the same amount of second messenger, ie more opioid is required

Question 3

Describe the mechanism of opioid withdrawal

Answer 3

• Opioid levels fall and as the opioid molecule leaves the receptor it is not replaced
• Second messenger activity falls
• Patient perceives pain as euphoria and analgesia not met

Question 4

What are the clinical signs of phaeochromocytoma?

Answer 4

-Sweating, tremor, anxiety and high blood pressure

Question 5

Why can b-blocker withdrawal occur?

Answer 5

• Prolonged exposure of the b-adrenorcptors to b-antagonists results in tachyphylaxis increasing receptor number and suprasensitivity of receptors
• Relative increase in sympathetic activity

Question 6

How does the sensitivity to catecholamines change with age?

Answer 6

-Decreases becoming less sensitive

Question 7

How do receptors become suprasensitive?

Answer 7

• Agonist deprivation

- Excessive exposure to an antagonist