1. Receptors 2. Receptor dynamics 3. Drug receptor binding 4. Agonists & Types of Agonists 5. Antagonists 6. Constants related to antagonists 7. Types of antagonists 8. Mechanisms of actions of receptors 9. Thank you

1. Agonist, Antagonist and
different type of antagonism
(PC-520)

2. Receptors
❑ Drugs usually do not bind directly with enzymes, channels,
transporters or structural proteins, but act through specific
macromolecules – RECEPTORS
❑ It is defined as a macromolecule or binding site located on cell
surface or inside the effector cell that serves to recognize the
signal molecule/drug and initiate the response to it, but itself has
no other function

3. Nature of receptors:
❑ Not hypothesis anymore – proteins and nucleic acids
❑ Isolated, purified, cloned and amino acid sequencing done
❑ Cell surface receptors remain floated in cell membrane lipids
❑ Non-polar hydrophobic portion of the amino acid remain buried in
membrane while polar hydrophilic remain on cell surface
❑ Major classes of receptors have same structural have same structural motif
– pentameric etc.
❑ But, majority of individual receptor molecules are made up of non-identical
subunits – ligand binding brings about changes in structure or alignment of
subunits.
❑ Binding of drugs in ligand binding domain induces conformational changes

6. IT IS JUST LIKE ANY RECEPTOR'S IDENTITY

7. Drug-Receptor binding

8. Drugs may interact with
receptors in several ways. The
effects resulting from these
interactions are diagrammed in
the dose-response curves at the
right. Drugs that alter the agonist
(A) response may activate the
agonist binding site, compete
with the agonist (competitive
inhibitors, B), or act at separate
(allosteric) sites, increasing (C) or
decreasing (D) the response to
the agonist. Allosteric activators
(C) may increase the efficacy of
the agonist or its binding affinity.
The curve shown reflects an
increase in efficacy; an increase in
affinity would result in a leftward
shift of the curve.
Drug-Receptor binding

9. Some common terms

11. Agonist type: its all relative

12. Affinity:

13. Potency:

14. Efficacy:

15. Full and partial agonist:

17. Inverse agonists:

18. Allosteric modulators:

19. Allosteric modulation. (A) Allosteric drugs bind at a separate site on the receptor to ‘traditional’ agonists (now often referred to as ‘orthosteric’ agonists). They can modify the activity of the
receptor by (i) altering agonist affinity, (ii) altering agonist efficacy or (iii) directly evoking a response themselves. (B) Effects of affinity- and efficacy-modifying allosteric modulators on the
concentration–effect curve of an agonist (blue line). In the presence of the allosteric modulator the agonist concentration–effect curve (now illustrated in red) is shifted in a manner
determined by the type of allosteric modulator until a maximum effect of the modulator is reached. (Adopted from Rang and Dale, 2019 Book).
Allosteric modulators:
(A) (B)

21. General classes of antagonists:

28. THE ANTAGONIST COMPETES WITH AGONIST BUT IT IS ACTUALLY
IRREVERSIBLE IN NATURE

36. Receptor binding
measurement:
**IF WE USE NON RADIOACTIVE LIGAND IN A
SATURATING CONCENTRATION THEN ONLY WE
WILL COME TO KNOW THAT WHERE ELSE DOES
IT GET BIND OTHER THAN JUST THE RECEPTOR
**

37. THANK YOU