Local mediators of inflamation

Question 1

How is histamine synthesised?

Answer 1

From Histidine.

By Histidine decarboxylase.

Question 2

What cells are histamine primarily found in?

Answer 2

Mast cells and basophils.

Question 3

How is Histamine released?

Answer 3

1. IgE binding to FcE receptor on mast cells.
   OR
2. C3a and C5a binding to mast cell receptor.
   OR
3. Morphine

Question 4

Effects of Histamine on its H1 receptor?

Answer 4

1. Capillary vasodilation due to smooth muscle contraction.

2. Contraction of endothelial cells in venules=> Increased permeability and oedema.

Question 5

Describe the histamine triple response.

Answer 5

Inject histamine:

1. Initial reddening of skin due to direct vasodilation by histamine (0-1min)
2. Larger/spread of reddening due to axon mediated vasodilation by histamine
3. Formation of a wheal due to localised oedema. (1-2mins)

Question 6

Inverse agonists vs antagonists?

Answer 6

Inverse agonists cause the opposite response. Antagonists inhibit the response.

Question 7

Examples of Antihistamines?

Answer 7

1. First gen.
   - Diphenydramine
   
   • Sedating (crosses BBB) and dry mouth.
2. Second gen.
   - Cetirizine
   - Loratidine
   - Non-sedating and fewer side effects.

Question 8

Uses of antihistamines?

Answer 8

Allergic rhinitis
Conjuctivitis
Asthma
Anaphylaxis

• Second gen are drugs of choice usually.
• *First gen must be used for motion sickness.

Question 9

Where is serotonin found?

Answer 9

GIT enterochrmaffin cells and platelets.

Platelets pick up serotonin from the GIT, GIT enterochromaffin cells create it.

Question 10

Functions of serotonin?

Answer 10

Increases GI Motility
Vasoconstriction in dmged vessels and vasodilation in undmged vessels
Enhances platelet aggregation
Pain and itching via action on sensory nerves
Drives organ dysfunction in sepsis
May play a role in peripheral vasc disease