Receptors

All important Receptors and it's Pharmacological action.

1. Prepared by-ShaguftaFarooqui
Assistant Professor
Department of Pharmacology
Nanded Pharmacy college,Nanded

2. Receptors
These are the molecules or binding site located on the surface or inside
the cell that recognise the signal molecule or drug and indicate the
response.
Chemically receptors are protein in nature .All the receptors are proteins
but all the proteins are not receptors.

3. Types of Receptors
G-Protein
Coupled
receptor
Ligand
gated ion
channel
receptor
Enzymatic
receptors
Nuclear
receptors

4. G-Protein Coupled
Receptors

5. TheGprotein-coupledreceptor(GPCR)superfamilycomprisesthelargestand
mostdiversegroupofproteinsinmammals.
Synonym:“seven-transmembrane”(7-TM),“serpentine”receptors,heptahelical
receptors,serpentinereceptor,andGprotein–linkedreceptors(GPLR)

6. Itisinvolvedininformationtransfer(signaltransduction)fromoutsidethe
cell to the cellular interior.
GPCRsareresponsibleforeveryaspectofhumanbiologyfromvision,taste,
senseofsmell,sympathetic and parasympathetic nervous
functions,metabolism,and immune regulationtoreproduction.
~45%ofallpharmaceuticaldrugsareknowntotargetGPCRs.

7. Adenyl cyclase pathway
ATP CAMP Inactive
Adenylcyclase Phodphodiesterase
Secondary Messenger

8. CAMP Effects on organ-
Cardiac muscle
Increases force of
contraction,IncreaseHeart
rate,IncreasesBlood
pressure.
Smooth muscle Smoothrelaxation
Adipose tissue
Lipolysis
Liver
Glycogenolysis

9. Phopholipase pathway
Stimulationofthispathwayresultsinthebreakdownofcellmembrane
phospholipids.
Phospholipidsuponbreakdownwillreleaseionsitol-1,4,5–triphosphate
(IP3)anddiaceylglycerol(DAG)whichactsasasecondarymessenger.

10. Sr no. Organ Pharmacologicalaction
1 Increases force of contraction,
Increase Heart rate, Increases Blood
pressure.
2 Smooth muscle contraction
3 Increase secretion
4 CNSstimulation

11. All G-protein couple receptors mediate pharmacological action through
release of second messenger ,but the type of second messenger is different
from one receptor to another receptor.
The type of second messenger will be identified by following representation.
G-protein Signalling pathway
Gs Increase CAMP
Gi Decrease CAMP
Gq Increase IP3,DAG

12. Example of G-Protein Coupled receptor
Sr no.Receptors Types
1 Muscarinicreceptors [M1-M5]
2 Adrenergic receptors [αand β]
3 Histamine receptors [H1-H3]
4 Dopamine receptors [D1-D5]
5 Opiodreceptors [μκб]
6 5-HT receptors 5-HT[1-7]except 5-
HT3
7 GABAB receptors GABAB

13. Muscarinicreceptors
M1 M5M3
M4M2
Gq
Gi

15. Receptors Organs Response effects
M1 Gastric Parietal
cells(oxynticcells)
2.Cilliarymuscles
of iris
Contraction of
Parietal cells,
Contractionof
muscle
increase acid
secretion
Decrease pupil
size
M3 Smooth muscle
a)Bronchi
b)Uterus
c)GIT
2.Glands
a)Sweat gland
b)Salivary gland
c)Lacrimal glands
a)constriction of
bronchi
b) constriction of
uterus
c) constriction of
GIT
a)Increase
secretion
b)Increase salivary
secretion
c)Lacrimal
secretion
c) Increase
peristalsis
M5 CNS Stimulation

16. Receptors organs Response
M2(Gi) Heart Decrease heart rate, Decreases
force of contraction,Decrease
cardiac output,
Decrease heart rate
M4(Gi) CNS Inhibitoryeffect on CNS

17. Acetylcholine is a neurotransmitter in parasympathetic nervous system
and this is also known as cholinergic nervous system.
Drugs which produces action similar to acetylcholine called as
parasympathetic or cholinomimetics or cholinergic drugs or agonist.
Drugs which block the action of acetylcholine called as
parasympatholytics/ Anti cholinergic drugs/cholinergic receptor
blockers.
Uses of Anticholinergicdrugs:
Anti
hypotensive
Bronchodilators Anti diarrheal Anti-ulcer

18. Anti
hypertensive
Constipation Achlorhydria
Uses of Cholinergic drugs:

19. Adrenergic Receptors
Alpha
Alpha1(Gq)
Blood
vessels
Alpha2(Gi)
CNS

20. Adrenergic Receptors
Sr no.Receptor Function
01 Beta1-Heart IncreaseForceofcontraction,
Increase blood pressure,
Increaseheartrate
02 Beta2-Smoothmuscle
Liver
Bronchi
Relaxation
Glycogenolysis
Bronchodilation
03 Beta3-Adipose tissue Lipolysis

21. Uses of Adrenergic drugs
Anti
hypotensive
Bronchodilators Antihistamine

22. Ionotropic Receptors
These receptors are also transcellular receptors. Here the receptors are
coupled to ion channel. When the ligandbinds to the receptors ,There will
be opening of ion channels will takes place that results in either influx or
efflux of ion depending upon concentration gradient and which will
produce pharmacological action.
Example of Ionotropicreceptors.
Srno.Examples of receptors
1 Nicotinic receptors
2 5-HT3 receptors
3 GABAA receptors
4. NMDA receptors

23. 1. Nicotinic receptors
Acetylcholine
Nm(Skeletal muscles)
Na+
Skeletal muscles Contraction

24. 2. 5HT3 receptors
5-HT(serotonin)
5-HT3(CTZ)
Na+
Vomiting

25. 3. GABAAreceptors
GABA
GABAA (CNS)
CL-
CNS Depression

26. 4.NMDA receptors
Aspartate and glutamate
NMDA(CNS)
Ca++
CNS Stimulation

27. Enzymatic Receptors
Thesereceptorsarecoupledtoenzymes.Therearealsotranscellular
receptors.
Whentheligandbindstoreceptors,enzymesautomatically
undergoesphosphorylation(Autophosphorylation)whichis
responsibleformediatingpharmacologicalaction.
Mostofthereceptorscoupledtotheenzymestyrosinekinase.
E.g-
1.Insulinreceptors-Tyrosinekinase
2.Growthfactorreceptors-Tyrosinekinase
3.Natriureticpeptidereceptors-Guanylcyclase

28. Nuclear Receptors
Here receptors are coupled to nucleus .These receptors are Intracellular .
When ligand
binds to receptors
Direct change in the gene
Expression (DNA)
Synthesis of specific m-
RNA
Synthesis of specific
protein
Produces
Pharmacological Action

30. Most of the steroidal drugs and steroidal hormones produces their actions
through nuclear receptors. Hence they are also called as steroidal receptors.
Example-
1.Glucocorticoidreceptors.
2.Mineral corticoid receptors
3.Estrogen receptors
4.Progesterone receptors
5.Testosterone receptors
6.ViamineA and Vitamin D
7.Thyroid hormone receptors.