This presentation discusses drug antagonism and neurotransmitters. It defines drug antagonism as one drug inhibiting the action of another drug, describing four types: physical, chemical, physiological/functional, and pharmacological antagonism. It then focuses on pharmacological antagonism, distinguishing between competitive and non-competitive receptor antagonism. The presentation also defines neurotransmitters as chemical signals released at synapses that activate receptors and transmit electrical signals between neurons. It classifies and describes several major neurotransmitters, including amino acids, monoamines, acetylcholine, and their functions in the brain and body. References used in creating the presentation are also listed.

1. S
1
A PRESENTATION
ON
DRUG ANTAGONISM &
NEUROTRANSMITTERS
PRESENTED TO-
Dr. SUDIPTA SAHA
ASSISSTANT PROFESSOR,
DEPARTMENT OF
PHARMACEUTICAL SCIENCES,
BBAU,LUCKNOW
PRESENTED BY-
YOGESH KUMAR
M.PHARM 1st year
(PHARMACOLOGY)
DEPARTMENT OF
PHARMACEUTICAL SCIENCES,
BBAU,LUCKNOW

2. DRUG ANTAGONISM
One drug or inhibits action of another drug
Types of Antagonism
a) Physical antagonism
b) Chemical antagonism
c) Physiological/functional antagonism
d) Pharmacological antagonism

3. A) Physical Antagonism
 Based on physical property of drugs, e.g. charcoal adsorb
alkaloid in alkaloidal poisoning
B) Chemical Antagonism
 Chemical reaction between two drugs
 e.g. Tetracycline with milk form Chelate & no response
shown.

4. C) Physiological/Functional
Antagonism
Opposite effects of two drugs on same function
 Two drugs act on two diff. types of receptors &
antagonize action of each other.
 e.g. Glucagon & Insulin given simultaneously both
drugs act as opposite to other.

5. D) Pharmacological Antagonism
 Opposite effect of two drugs binding to same receptors
 Receptor antagonism is specific,e.g. atropine  spam of
intestine by acetylcholine not by Hist.or 5-HT
Types
Competitive Non-competitive
Equilibrium Non-equilibrium
(Reversible) (Irreversible)

6. A) Competitive Antagonism
i) equilibrium or reversible
Competition between agonist & antagonist for
specific site or receptor
 Bind Non-covalently & action of agonist is blocked if
conc. of antagonist is 
 Antagonism can be overcome (surmount) by  conc.
of agonist
Cont.

7.  Agonist can produce max.response in higher conc.
 Competitive antagonist shifts log Dose-response curve of
agonist to right
 EC50 of agonist  in presence of antagonist, e.g., Ach &
atropine; Ad & Prop.; Morphine & naloxone

8. ii) Non-Equilibrium(irreversible)
Antagonist
 Antagonist binds to receptor with covalent bond
 Irreversible blocking
 Antagonist shifts DRC to right+  max. response, e.g.
adrenaline & phenoxybenzamine

9. B) Non-competitive
(non-surmountable Antagonist)
 Antagonist binds to another site of receptor
 DRC is flattened + max. response is 
 e.g., Flumazenil antagonize the action of GABA by binding
to another site.

10. Non-competitive Antagonist

11. NEUROTRANSMITTERS

12. NEUROTRANSMITTERS
 DEFINITION: Neurotransmitters are chemical
transducers which are released by electrical impulse
into the synaptic cleft from presynaptic membrane
from synaptic vesicles. It then diffuse to the
postsynaptic membrane and react and activate the
receptors present leading to initiation of new electrical
signals.
 In other words a substance i.e.released at a synapse by
a neuron & that effects another cell,either a neuron or
an effector organ,in a specialized manner.
 Otto Loewi,an Austrian scientist discovered the first
neurotransmitter in 1921.

13. Classic Characteristics:
 Synthesized in the neuron.
 Become localized in presynaptic terminal.
 Bind to receptor site on postsynaptic membrane.
 Removed by a specific mechanism from its specific site
of action.

14. Classification
 Small molecule transmitters:
Amino acids:
Dietary amino acids.
GABA
Monoamines:
Catecholamines.
Indoleamines.
 Acetylcholine.

15. Amino Acids
 Dietary:
Aspartate.
Glycine.
 Gamma aminobutyric acid (GABA):
From decarboxylation of glutamate.

16. Monoamines
 Catecholamines:
Derived from tyrosine.
Include:
Dopamine.
Norepinephrine.
Epinephrine.
 Indoleamine:
Derived from tryptophan.
Includes:
Serotonin.

17. Glutamate
 Found in:
Cerebral cortex.
Striatum.
Dentate gyrus (hippocampus).
Cerebellum.
Spinal cord.
 Excitatory influences on basal nuclei.

18. Aspartate
 Found throughout brain and spinal cord.
 Effects are usually excitatory.
Glycine
 Found in:
Interneurons of spinal cord:
Renshaw cells.
Neurons of subthalamic nuclei projecting to globus
pallidus.

19. GABA
 Found in:
Granule cells of olfactory bulbs.
Amacrine cells of retina.
Purkinje cells and basket cells of cerebellum.
Hippocampus.
Basal ganglia.
Numerous interneurons.

20. Dopamine
 Also found in:
Neurons from hypothalamus to hypophysis.
Retina:
Role in lateral inhibition (focusing effect).
Olfactory bulb.

21. Norepinphrine
 Found in:
Locus ceruleus and Lateral tegmental nuclei.
Neurons to:
Midbrain tectum.
Thalamus, hypothalamus
Cerebral cortex, Cerebellar cortex
Medulla and spinal cord
Most postsynaptic sympathetic
neurons.

22. Norepinphrine Functions
 Modulator– sets brain tone.
 Suppresses irrelevant stimuli.
 Enhances relevant stimuli.
 Modifies behavior, arousal, degree of alertness, ECG
activity and sleep.
 Role in mood, memory.
 Hormone regulation and homeostasis.

23. Serotonin
 Only present in cell bodies of neurons located primarily
in the raphe and reticular formation (limited) of
brainstem.
 Inactivated by MAO.
Serotonin Functions (?)
 Inducing sleep.
 Pain transmission.
 Certain psychotic disorders:
Depression.
 Total amnesia may occur when:
Raphe neurons are destroyed.
Serotonin stores are depleted by reserpine.

24. Acetylcholine
 Choline is made in liver, not brain.
 Synthesized by choline acetyltransferase:
Synthesized within neuron cell body.
 Degraded by acetylcholinesterase:
Synthesized within neuron cell body.

25. 25
Nicotinic Muscarinic
1 Found at:
i. Neuromuscular junction of
skeletal muscle
ii. Postganglionic neurons of
parasympathetic nervous
system.
iii. Ventral tegmental area.
i. Glands
ii. Neuromuscular junctions of
cardiac and smooth muscle.
iii. Postganglionic neurons of
sympathetic nervous system.
2 Agonist Nicotine Muscarine ( a toxin produced by
certain mushroom)
3 Antagonist Curare ( paralyses skeletal
muscle)
Atropine
Acetyl Choline Receptors

27. REFRENCES
 Rang & Dale; Pharmacology book.
 Goodman & Gilman’s the Pharmacological basis of
Therapeutics
 Katzung;Pharmacologgy:10th edition
 K,D tripathi;Essentials of Pharmacology.
 Internet source.
 etc.

28. THANK YOU