Adrenergic Receptors and Signaling

Question 1

What is the receptor class of α₁ receptors?

What are the major associated signaling components?

Answer 1

GPCR (G_q)

increased PLC and PKC activity

increased conversion of PIP₂ into IP₃/DAG

increased [Ca²⁺]

Question 2

What is the receptor class of α₂ receptors?

What are the major associated signaling mechanisms?

Answer 2

GPCR (G_i)

decreased adenylyl cylase and PKA activity

decreased [cAMP]

Question 3

What is the receptor class of β₁ receptors?

What are the major associated signaling components?

Answer 3

GPCR (G_s)

increased adenylyl cylase and PKA activity

increased [cAMP]

Question 4

What is the receptor class of β₂ receptors?

What are the major associated signaling components?

Answer 4

GPCR (G_s)

increased adenylyl cylase and PKA activity

increased [cAMP]

Question 5

What is the receptor class of D₁ receptors?

What are the major associated signaling components?

Answer 5

GPCR (G_s)

increased adenylyl cylase and PKA activity

increased [cAMP]

Question 6

What is the receptor class of D₂ receptors?

What are the major associated signaling components?

Answer 6

GPCR (G_i)

decreased adenylyl cylase and PKA activity

decreased [cAMP]

Question 7

What are the major effects of α₁ receptor stimulation?

Answer 7

Heart:

• increases force of contraction
• reflex bradycardia

Vasculature:

-contraction -> increases BP

Eyes:

-dilation (mydriasis)

GU:

-prostate and urtethral contraction -> urinary retention

Question 8

What are the major effects of α₂ receptor stimulation?

Answer 8

Nerves:

-inhibits adrenergic and cholinergic nerve synapes (sympatholytic)

Eye:

-decreases aqueous humor production from ciliary body

Fat:

-decreases lipolysis

Pancreas:

-decreases insulin release

Question 9

What are the major effects of β₁ receptor stimulation?

Answer 9

Heart:

-increases force and rate of contraction (increase cardiac output)

Kidney:

-increases renin release

Question 10

What are the major effects of β₂ receptor stimulation?

Answer 10

Smooth muscle relaxation:

• lungs -> bronchodilation
• vasculature -> decreased BP
• GI -> decreased motility
• bladder detrusor -> decreased urination
• uterus

Liver:

-increases gluconeogenesis and glycogenolysis

Pancreas:

-increases insulin release

Muscle:

-increases potassium uptake -> decreases plasma [K⁺]