Histamine Agonists

Question 1

How are histamine agonists formed

Answer 1

Decarboxylation of L-histidine

Question 2

What kind of receptors do they bind

Answer 2

G protein

Question 3

G protein for H1

Answer 3

Gq

Question 4

G protein for H2

Answer 4

Gs

Question 5

Most prominent effect of histamine agonists

Answer 5

Vasodilation (H1 and H2)

Question 6

Where is H1 located

Answer 6

Endothelium, SM, nerve endings

Question 7

Where is H2 located

Answer 7

Gastric mucosa, Cardiac muscle cells, immune cells

Question 8

What is the action of H3

Answer 8

Reduce NT release from histaminergic and other neurons

Question 9

What is the action of H4

Answer 9

Chemotactic for EOS and mast
On WBCs in BM and blood
Inflammation and allergies

Question 10

Is the histamine receptor constitutive

Answer 10

Yes

Question 11

What is the histamine triple response

Answer 11

Localized red spot
Flare
Wheal

Question 12

What mediates GIT contraction and bronchconstriction

Answer 12

H1

Question 13

CVS action of H2

Answer 13

Increase contractility and HR

Question 14

CVS action of H1

Answer 14

Increase capillary permeability
Edema
Urticaria

Question 15

What H receptor stimulates nerve endings causing pain and itching

Answer 15

H1

Question 16

Which receptor mediates gastric acid secretion

Answer 16

H2

Question 17

Clinical use of histamine

Answer 17

Pulmonary function testing

Question 18

Histamine Contraindications

Answer 18

Asthmatics

Peptic ulcer disease/GI bleed

Question 19

Main AE of histamine

Answer 19

Anaphylaxis

Question 20

Immunological method of histamine release

Answer 20

Ag → IgE (on mast) → degranulation and release

Ca mediated

Question 21

Chem/Mech method of histamine release

Answer 21

Morphine/Tubocurarine (amines) displace histamine from heparin complex