1.
Inflammation
Part 4

2.
MEDIATORS OF
INFLAMMATION
Histamine & Serotonin

3.
Overview
• General Properties
• Types of mediators
• Histamine and Serotonin

4.
Mediators of inflammation
These are the substances that
INITIATE REGULATE&
Inflammatory reactions

5.
General properties
These mediators can be produced
Locally, by the CELLS Derived from inactive
precursors present in plasma
CELL- DERIVED PLASMA -DERIVED
Preformed/
Ready made!
Synthesised de
novo/
made if needed!
1

6.
They can be produced only in
response to agents that stimulate
inflammation
They can stimulate the release of
another mediator
They have short lifespan!
They can act on wide variety of cells
2
3
4
5

7.
Preformed Synthesised de novo
• Histamine
• Serotonin
• Arachidonic acid
metabolites
• Platelet activating
factor
• NO
• Reactive oxygen
species
• Cytokines
• Chemokines
Compliment
activation
Factor XII
activation
• C3a
• C3b
• C5a
• Coagulation
system
• Kinin system
Cell - Derived Plasma - Derived
CHEMICAL MEDIATORS
OF INFLAMMATION

8.
HISTAMINE & SERATONIN
Vasoactive amines
Are the first mediators to be released during inflammation
Once formed it can be either stored or rapidly inactivated
Derived from the decarboxylation of the amino acid histidine

9.
Sources
Mast cells
Basophils
Platelets
Stimulus
Substances inducing inflammation like
heat,cold, irradiation,trauma etc
C3a & C5a: Anaphylatoxins
IL-1 & IL8.
Histamine releasing factors from cells
like neutrophils, monocytes and
Platelets.

10.
ACTIONS
Increase in Vascular permeability
By Increasing Blood Flow and
Endothelial Barrier Disruption
Vasodilatation
It is responsible for the Wheal &
Flare reaction in the skin.
Responsible for itching and pain
Also mediates bronchial Asthma
and anaphylactic shock
Resulting from nitric oxide
release
Contraction of extravascular
smooth muscles eg:bronchus
By the excitation of a subset of
unmyelinated C-fibers which are
pruriceptive.

11.
SEROTONIN
5- Hydroxytryptamine
Stored in platelets and mast cells
Also in chromaffin cells of GIT, spleen and nervous tissue
Actions are similar to Histamine but less potent.

12.
Summary
• General Properties
• Types of mediators
• Histamine and Serotonin

13.
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