Classification and localization of adrenoceptors

Question 1

Receptor subtype: Alpha 1
Localization
Effect

Answer 1

Localization:
1.Vascular smooth muscles
(skin, mucosa, kidneys)- Vasoconstriction
2. Sphincters of GI and GU tract - Constriction
3. Eye (radial muscle of the iris) - Constriction,
dilation of pupil

Question 2

Receptor subtype: Alpha 2
Localization
Effect

Answer 2

1. Sympathetic nerve endings
   (presynaptic) - decrease release of norepinephrine
2. Brainstem (nucleus tractus solitarius) - decrease sympathetic nervous system activity
3. Vascular smooth muscle - Vasoconstriction
4. Platelets- Aggregation

Question 3

Receptor subtype: Beta 1
Localization
Effect

Answer 3

1. Heart - increase heart rate and contractility

2. Juxtaglomerular cells- increases renin secretion

Question 4

Receptor subtype: Beta 2
Localization
Effect

Answer 4

1. Bronchial smooth muscle - Bronchodilation
2. Vascular smooth muscles (vessels in skeletal muscles) - Vasodilation
3. GI and GU smooth muscles (wall) - Relaxation
4. Uterus - Relaxation
5. Liver decreases glycogenolysis

Question 5

Receptor subtype: Beta 3
Localization
Effect

Answer 5

1. Adipose tissue - increases lipolysis

2. Smooth muscles in urinary bladder - Relaxation