Transcript No Slide Title

Neurotransmitters,
Neuromodulators, and their
receptors
The following slides provides a summary of the major classes of
neurotransmitters and the names of the receptors that have been
identified. The drugs listed in these slides are drugs that affect
neuronal transmission by attaching to the post and pre-synaptic
receptors. Other drugs (not listed in these slides) affect neuronal
functioning by altering some other function of a neuron.
Neurotransmitters (NT) & Neuromodulators (NM)
1. Acetylcholine (NT)
A. Catecholamines
•Dopamine
2. Monoamines (NT; NM)
•norepinephrne
•epineprine
B. Indolamines
•Serotonin
3. Amino Acids (NT; NM)
• Glutamate
• GABA
• Glycine
4. Peptides (NT; NM)
5. Lipid-like substances (NT)
6. Nucleosides (NM)
7. Soluble gases
(atypical)
Endorphins, enkephalins
Anandamide, leptin
adenosine
Nitric Oxide, Carbon Monoxide
Types of drugs base on their
effects on receptors
Agonist - a drug that binds with and
activates a postsynaptic receptor.
Antagonist - a drug that binds with a
postsynaptic receptor and does not activate
it; may block the natural transmitter from
binding with the receptor
Different subtypes of Agonists and antagonists are described
on the next slide
(also called Receptor Blocker)
(A better but never used term is
indirect antagonist)
Receptor subtypes
Receptors belonging to one class of neurotransmitters
(e.g. Dopamine) may respond differently to various
drugs. When this is the case the receptors are divided
into subclasses.
E.g. There are several Dopamine receptors, each
responding to dopamine but differently to different
drugs. These receptors are called D1, D2, D3, D4, and
D5 receptors
1. Acetylcholine (cholinergic or acetylcholinergic neurons)
Competitive agonist & antagonists
Agonist
Nicotinic Receptor Nicotine
Muscarinic Receptor Muscarine
Antagonist
Curare
Atropine
2. Monoamines
A.Catecholamines (primarily neuromodulators)
1. Dopamine (Dopaminergic neurons; produces EPSPs or
IPSPS)
Agonist
Antagonist
D1 – D5
Apomorphine
Chlorpromazine
Receptors
(note: this drug is an
(D2)
antagonist of
autoreceptors, but because
neuronal activity is
facilitated it is classified
as an Da agonist)
2.
Norepinephrine (Noradrenergic neurons)
Agonist
Antagonist
Clonidine
1, 2; 1,2
Yohimbine (2)
Receptors
(2)
3. Epinephrine (Adrenergic neurons)
2. Monoamines
B. Indolamines
1. Serotonin (5-HT; Serotonergic neurons)
A1, A2
Agonist
Floxetine
(Prozac)
Antagonist
PCPA
3. Amino Acids
A.Glutamate (glutamatergic neurons)
Principle Excitatory neurotransmitter in brain
& spinal cord
NMDA receptor
(ionotropic)
Agonist
NMDA
AMPA receptor
AMPA
(ionotropic)
Kainate receptor Kainate acid
(ionotropic)
metabotropic
--receptor
comments
6 binding sites; controls
Na+ & Ca++;
EtOH binding site?;
PCP ("angel dust") is
antagonist
Most common; controls
Na+
controls Na+
May be 6 or more of
these; some are
autoreceptors
3. Amino Acids cont.
B. GABA (GABA-secreting neurons)
- Principle Inhibitory neurotransmitter in brain & spinal
cord
- Drugs at Sites 2-5 acts as noncompetitive
agonists/antagonists
- B-CCM may be a natural transmitter for the
benzodiazepine site.
GABA A
Ionotropic
Controls Clchannel
Agonist
Site 1: GABA
Site 2: Benzodiazepines
(Valium; Librium, alcohol?) –
Anxiolytics
Site 3: Barbiturates
Site 4: steroids
Antagonists
Site 5: picrotoxin
(inverse agonist)
GABA B
Metabotropic
Controls K+
channel
Baclofen (opens K+
channels)
3. Amino Acids cont.
C. Glycine
Inhibitory neurotransmitter in the spinal cord & lower
brainstem
Glycine receptor
Agonist
strychnine
Antagonists
none
4. Peptides
- Chains of two or more amino acids
- produced from larger polypeptide chains (precursor
molecules)
- no reuptake or recycling of peptides
- serve as neurotransmitters and neuromodulators
e.g., endogenous opioid peptides (endorphins,
enkephalins)
Agonist
Mu opiate receptor Morphine, heroin,
Percodan
Delta opiate receptor
Kappa opiate receptor
Antagonists
naloxone
5. Lipid-like substances
A.anandamide
THC receptor
Agonist
THC
Antagonists
?
Agonist
?
Antagonists
?
B. Leptin
Leptin receptor
6. Nucleosides (sugar molecule +purine or pyrimidine)
e.g., adenosine
- serves as a neuromodulator
- released by adenosinergic neurons & glial cells
- produces inhibitory effects by opening K+ channels
3 types of
metabotropic receptors
Agonist
?
Antagonists
Caffeine
7. Soluble Gases
- produced in several regions of neurons including
dendrites
- released as soon as produced
- dilates blood vessels in active brain areas and
causes penile erection
- enters cells and activates second messenger cyclic
GMP
A. nitric oxide (NO)
B. carbon monoxide (CO)