The document discusses neurotransmitters and their functions. It describes how neurotransmitters allow communication between neurons through secretion and reception. Some key neurotransmitters discussed include acetylcholine, catecholamines like dopamine and norepinephrine, serotonin, GABA, histamine, glycine, glutamate, and nitric oxide. The document also outlines the clinical importance of some neurotransmitters, with examples of conditions treated by agents that modulate neurotransmitter systems like Parkinson's disease, Alzheimer's disease, depression, and allergies.

1. M.Prasad Naidu
MSc Medical Biochemistry,
Ph.D.Research Scholar

2.  Neurotransmitters is a chemical substance or chemical
messenger (within brain) that is secreted by neurons and
that allow communication between nerve cells to produce
physiological response such as muscle contraction.
 Neurotransmitters are chemical substances secreted by
neurons and they convey messages from one neuron to a
target cell.
 At the target cells, the neurotransmitters may alter ion flow
(depolarise or hyperpolarise), or they may alter the cellular
metabolism.
 The transmitter substances carry out the actual passage of a
signal across a synapse.

3.  Neurotransmitters are the principal signal molecules that
mediate their actions via receptors that can function as ion
channels.
The neuron
 The neuron is the structural and functional unit of the
nervous system.
 Neurons function by the production, propagation and
transfer of nerve impulses.
 The functional components of a neuron consists of
- the cell body (perikaryon) having the nucleus (karyon) and
those organelles that maintain the cell.
- the processes extending from the cell body which consists
of axon and dendrites.

5.  Synapses
 A Synapse is a site of functional contact between neurons
that facilitate transmission of impulses from one
(presynaptic) neuron to another (postsynaptic) neuron or
effector (target) cells such as muscle and gland cells.
 Synapse is a site of neuron-to-neuron or neuron-to-effector
cell communication.
 A typical Synapse contains presynaptic bouton or knob,
synaptic cleft and postsynaptic membrane.

9.  Classification of neurotransmitters
 Class Amine –
 Examples are epinephrine, norepinephrine, dopamine and
serotonin (5-hydroxytryptamine).
 Class Amino acid and amino acid derivatives –
 Examples are glutamate, aspartate, glycine, histamine and
GABA.
 Class Purines –
 Examples are adenosine, ATP.
 Class Gas –
 Examples are nitric oxide
 Class Miscellaneous

10.  Examples are acetylcholine
 Acetyl choline
 Acetylcholine
 The first chemical neurotransmitter identified was
acetylcholine.
 Synthesis and storage
 Release and action
 Reuptake and degradation
 Acetylcholine receptors – muscarinic and nicotinic
acetylcholine receptors.
 Cholinergic agonists are nicotine, muscarine and α-
latrotoxin.

11.  Cholinergic antagonists are atropine (and related compound
scopolamine), botulinus toxin, α-bungarotoxin and d-
tubocurarine (muscle relaxant).


16.  Catecholamines
 The principal catecholamines are norepinephrine
(noradrenaline), epinephrine (adrenaline) and dopamine.
 Synthesis
 Storage
 Release
 Receptors and action
 Reuptake and degradation
 Functions of catecholamines

20.  Serotonin
 Serotonin also called 5-hydroxytryptamine (5-HT).
 Storage and release
 Reuptake and degradation
 Functions

22.  GABA (Gamma Aminobutyric Acid)
 Synthesis
 Receptors and action
 Reuptake and degradation
 Functions of GABA

24.  Histamine
 Synthesis and receptors
 Functions
 Degradation

26.  Glycine
 Glycine is the inhibitory neurotransmitter in the spinal cord.
 Receptors and action
 Reuptake and degradation
 Functions of glycine

27.  Glutamate
 Glutamate is the excitatory amino acid neurotransmitter in
the brain.
 Receptors and action
 Reuptake and degradation
 Functions

28.  Nitric oxide (NO)
 Nitric oxide also has been identified as a neurotransmitter.
 Synthesis
 Degradation
 Functions

29.  Clinical importance
 Acetylcholine agonists with acetylcholinesterase inhibitors
have significant medical application in the treatment of
disorders such as
- glaucoma by increasing the tone of the muscles of
accomodation of the eye.
-myasthenia gravis
-in terminating the effects of neuromuscular blocking agents
such as atropine.

30.  Myasthenia gravis – auto antibodies form to nicotinic type
acetylcholine receptors which destroy some receptors and
compete with acetylcholine to bind to the surviving
receptors.
 Treatment may include administration of acetylcholine
esterase inhibitors (e.g., pyridostigmine, neostigmine) to
prolong activity of acetylcholine at motor end plates.
 Alzheimer’s disease – tacrine used in treatment of
alzheimer’s disease is a long-acting cholinesterase inhibitor.

31.  Catecholamines
 β – blockers, such as atenolol, are used to treat hypertension
and chest pain (angina) in ischaemic heart disease because
they antagonise the stimulatory effects of catecholamines on
the heart.
 β2 – receptor agonists such as salbutamol which stimulates β
– receptor of lungs, are used to produce bronchial dilation in
asthma without stimulating β1 – receptor in the heart.
 D2 – receptors (of dopamine) antagonist such as
phenothiazines and haloperidol are used as a antipsychotic
drugs.

32. • Parkinson’s disease
• Treatment may involve administration of
(i) Drugs such as deprenyl that inhibit the degradation of
dopamine and other biogenic amines by monoamine
oxidase type B
(ii) L-dopa that can cross the blood-brain barrier and serve as
a substrate for dopamine biosynthesis in striatal cells.

33.  GABA
 The anxiolytic drugs like diazepam and barbiturate, sleep
inducing and an anticonvulsant drug used in the treatment
of epilepsy, exert their soothing effects by potentiating the
binding of GABA to GABA-A receptors.

34. • Serotonin
• Depression
• Treatment may include administration of tricyclic anti-
depressants that inhibit uptake of both noradrenaline and
adrenaline into brain cells, or other antidepressants such as
fluoxetine (prozac) that preferentially inhibit serotonin
uptake inhibitors of monoamine oxidase A that convert
serotonin to an inactive aldehyde may also be used.

35.  Histamine
 H1 – receptors antagonists such as diphenhydramine are used
in the treatment of allergic responses and for asymptomatic
treatment of upper respiratory disorders.
 H2 – receptors antahonists such as ranitidine or cimtidine are
used in the treatment of peptic ulcers.
 H2 – receptor inhibitors have no effect on allergy.

36. Thank you