Neurotransmitters are endogenous chemical messengers that enable neurotransmission between neurons. They are synthesized in the presynaptic neuron, stored in vesicles, and released into the synaptic cleft upon an action potential. This triggers a response in the postsynaptic neuron by binding to receptors. Neurotransmitters are then removed from the synaptic cleft via reuptake or degradation. They can be classified functionally as excitatory, inhibitory, or both, or chemically based on their molecular structure such as amino acids, peptides, biogenic amines, gases, and others.

1. NEUROTRANSMITTER
Definition:-
 Neurotransmitter is an endogenous
chemical substance that enable
neurotransmission.
It is a type of chemical messenger, which
transmit signals across a neuronal synapse
between the neurons or at NMJ.
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2. PROPERTIES OF NEUROTRANSMITTERS
1) Synthesized in the presynaptic neuron
2) Localized to vesicles in the presynaptic neuron
3) Released from the presynaptic neuron under
physiological condition
4) Rapidly removed from the synaptic cleft by
uptake or degradation
5) Presence of receptor on the post-synaptic
neuron.
6) Binding to the receptor elicits a biological
response
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3. Classification of NT
there are two types of classifications:
They are
1. Functional classification
2. Chemical classification
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4. 1.Functional classification
3 types
a. Excitatory :
epinephrine,norepinephrine,glutamate
(fast),hisamine,aspartic acid.
b. Inhibitory:
GABA(fast), glycine.
c. Both excitatory and inhibitory:
Acetylcholine, dopamine,seratonin
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5. 2.Chemical classification
• Amino acid derivatives-
aspartic acid, glycine, glutamate, GABA, histamine
• Neuropeptides-substance P, neuropeptide Y, vaso intestinal
peptide,neurotensin,vasopressin,oxytocin,somatostatin,endorphins
,enkephalins,gastrin,cholecystokinin,LHRH (leutinizing hormone
releasing hormone)
• Biogenic amines- Norepineprine, epinephrine, dopamine,
seratonin,histamine
• Choline derivatives-acetylcholine
• Purines- Adenosine,ATP
• Gases-Nitric oxide (NO), carbon monoxide (CO)
• Miscellaneous-endocannabinoids
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7. Mechanism of action
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8. Steps in neurotransmitter processing are:
Synthesis: Neurotransmitters are synthesized by the
enzymatic transformation of precursors.
Storage: They are packaged inside synaptic vesicles.
Release: They are released from presynaptic terminal
by exocytosis when calcium enters axon terminal
during an action potential Diffuse across the synaptic
cleft to the postsynaptic membrane.
Binding: They bind to receptor proteins.
Inactivation: The neurotransmitter is degraded either
by being broken down enzymatically, or reused by
active reuptake.
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