Neurotransmitters, Neuromodulators, and their receptors The following slides provides a summary of...
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Transcript of Neurotransmitters, Neuromodulators, and their receptors The following slides provides a summary of...
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)
2. Monoamines (NT; NM)
3. Amino Acids (NT; NM)
4. Peptides (NT; NM)
5. Lipid-like substances (NT)
6. Nucleosides (NM)
7. Soluble gases
A. Catecholamines
B. Indolamines
•Dopamine
•norepinephrne
•epineprine
•Serotonin
• Glutamate• GABA
• GlycineEndorphins, enkephalins
Anandamide, leptin
adenosine
Nitric Oxide, Carbon Monoxide(atypical)
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 AntagonistNicotinic Receptor Nicotine Curare
Muscarinic Receptor Muscarine Atropine
A. Catecholamines (primarily neuromodulators)
1. Dopamine (Dopaminergic neurons; produces EPSPs orIPSPS)
Agonist AntagonistD1 – D5Receptors
Apomorphine(note: this drug is an
antagonist ofautoreceptors, but because
neuronal activity isfacilitated it is classified
as an Da agonist)
Chlorpromazine(D2)
2. Norepinephrine (Noradrenergic neurons)Agonist Antagonist
1, 2; 1,2Receptors
Clonidine(2)
Yohimbine (2)
3. Epinephrine (Adrenergic neurons)
2. Monoamines
B. Indolamines
1. Serotonin (5-HT; Serotonergic neurons)
Agonist AntagonistA1, A2 Floxetine
(Prozac)PCPA
2. Monoamines
A. Glutamate (glutamatergic neurons)Principle Excitatory neurotransmitter in brain& spinal cord
Agonist commentsNMDA receptor
(ionotropic)NMDA 6 binding sites; controls
Na+ & Ca++; EtOH binding site?;PCP ("angel dust") is
antagonistAMPA receptor
(ionotropic)AMPA Most common; controls
Na+Kainate receptor
(ionotropic)Kainate acid controls Na+
metabotropicreceptor
--- May be 6 or more ofthese; some areautoreceptors
3. Amino Acids
B. GABA (GABA-secreting neurons)- Principle Inhibitory neurotransmitter in brain & spinalcord- Drugs at Sites 2-5 acts as noncompetitiveagonists/antagonists- B-CCM may be a natural transmitter for thebenzodiazepine site.
Agonist AntagonistsGABA A Site 1: GABAIonotropicControls Cl-channel
Site 2: Benzodiazepines(Valium; Librium, alcohol?) –AnxiolyticsSite 3: BarbituratesSite 4: steroids
Site 5: picrotoxin(inverse agonist)
GABA BMetabotropic Controls K+channel
Baclofen (opens K+channels)
3. Amino Acids cont.
C. Glycine
Inhibitory neurotransmitter in the spinal cord & lowerbrainstem
Agonist AntagonistsGlycine receptor strychnine none
3. Amino Acids cont.
- 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 AntagonistsMu opiate receptor Morphine, heroin,
Percodannaloxone
Delta opiate receptorKappa opiate receptor
4. Peptides
A. anandamideAgonist Antagonists
THC receptor THC ?
B. LeptinAgonist Antagonists
Leptin receptor ? ?
5. Lipid-like substances
e.g., adenosine- serves as a neuromodulator- released by adenosinergic neurons & glial cells- produces inhibitory effects by opening K+ channels
Agonist Antagonists3 types ofmetabotropic receptors
? Caffeine
6. Nucleosides (sugar molecule +purine or pyrimidine)
- produced in several regions of neurons includingdendrites
- 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)
7. Soluble Gases