1. RECEPTORS
Vaheeda rahman, (PhD),.
Dept of pharmacology.
VISTAS

2. WHAT IS A RECEPTOR

3. RECEPTOR: It is a specific binding site on the cell which exhibits
some functional groups which trigger the
pharmacological action

4. AFFINITY: Ability of agent to combine with receptor
INTRINSIC ACTIVITY: Ability of agent to activate the receptor
(efficacy)
AGONIST: maximum affinity and efficacy
ANTAGONIST: having affinity but no efficacy
INVERSE AGONIST: having affinity and negative efficacy

6. Types of receptors:  Iono tropic receptors
 G-protein coupled receptors
 Enzymatic receptors
 Nuclear receptors

7. Ionotropic receptors:

8. G PROTEIN COUPLED RECEPTORS:
General Structure of receptors:

9. Structure of G-protein:

10. G protein coupled with receptors:

12. Adenyl cyclase pathway:

13. Step by step mechanism of G protein coupling and enzyme activation

14. Phospholipase C pathway:

15. Second messengers:
cAMP
system
Phosphoinositol
system
Arachidonic
acid system
cGMP
system
Tyrosine
kinase
system
receptor α2,β1,β2
M2
α1
M1,M3
Histamine - -
Transducer Gs(β1,β2)
Gi(α2,
M2)
Gq Unknown G-
protein
- -
Primary
effector
AC Phospholipase
C
Phospholipase
A
Guanylate
cyclase
Tyrosine
kinase
Secondary
messenger
cAMP IP3,DAG Arachidonic
acid
cGMP Protein
phosphatase
Secondary
effector
Protein
kinase A
Ca++ release 5-lipoxygenase Protein
kinase G
-

16. Examples of G-protein receptors:
 Muscarnic receptors (cholinergic)
 Adrenergic receptors (α,β)
 Histamine receptors
 Dopamine receptors
 Opiate receptors
 Serotonin receptors (all except 5-HT3)
 GABAB receptors

17. Enzymatic receptors:

18. Nuclear receptors:

19. Examples of nuclear receptors:
 Glucocorticoid receptors
 Minero corticoid receptors
 Oestrogen receptors
 Progestero receptors
 Androgen receptors
 Vit A and vit B receptors
 Thyroid hormone receptors

20. Other receptors:
Spare receptors: Maximum response is observed even though when all the
receptors of tissues are not occupied by drug moiety
Orphan receptors: Receptors with no endogenous ligand
Eg: PPAR-α receptors (peroxysomal proliferated activated receptors)
Silent receptors: Biologically silent even though stimulations of receptors
taking place no biological response
Normal receptors: Response observed when all the receptors of the
tissue occupied by drug moiety

21. REFERENCE:
 Pharmacology by RANG and DALE
 Integrated pharmacology by WALKER
 pharmacology by LIPPINCOTT
 pharmacology by BERTRUM
 www.wikkipedia.org
 www.winona.edu
 www.pharmacologycorner.com
 www.psychopharmacologyinstitute.com