Download presentation
Presentation is loading. Please wait.
1
Chapter 6 Neurotransmitter Systems
2
Introduction Three classes of neurotransmitters –Amino acids, amines, and peptides Ways of defining particular transmitter systems: –By the molecule, synthetic machinery, packaging, reuptake and degradation, etc. Acetylcholine (Ach) – First identified neurotransmitter Nomenclature (-ergic) –Cholinergic and noradrenergic
3
Henry Dale – received the Nobel Prize for Medicine in 1926 for his work on synaptic transmission. He is also well known for his coining of the term “cholinergic.”
5
Studying Transmitter Localization Immunocytochemistry – localize molecules to cells
8
In situ hybridization –Localize synthesis of protein or peptide to a cell (detect mRNA)
12
Muscarine – a type of poison found in some mushrooms
13
Moto-Taxi Driver (1999) at a coffee shop in Bangalore, India He is stimulating his nicotinic receptors.
16
A farmer harvesting opium poppies.
18
Studying Neurotransmitter Systems Neurotransmitter - three criteria –Synthesis and storage in presynaptic neuron –Released by presynaptic axon terminal –Produces response in postsynaptic cell Mimics response produced by release of neurotransmitter from the presynaptic neuron
19
Studying Transmitter Release –Transmitter candidate: Synthesized and localized in terminal and released upon stimulation –CNS contains a diverse mixture of synapses that use different neurotransmitters –Brain slice as a model Kept alive in vitro Stimulate synapses, collect and measure released chemicals
20
Studying Synaptic Mimicry –Qualifying condition: Molecules evoking same response as neurotransmitters –Microionophoresis: Assess the postsynaptic actions –Microelectrode: Measures effects on membrane potential
21
Studying Receptor Subtypes –Neuropharmacology Agonists and antagonists e.g., ACh receptors –Nicotinic, Muscarinic Glutamate receptors –AMPA, NMDA, and kainite
22
–Ligand-binding methods Identify natural receptors using radioactive ligands Can be: Agonist, antagonist, or chemical neurotransmitter
23
–Molecular analysis- receptor protein classes –Transmitter-gated ion channels »GABA receptors »5 subunits, each made with 6 different subunit polypeptides –G-protein-coupled receptors
24
Neurotransmitter Chemistry Evolution of neurotransmitters –Neurotransmitter molecules Amino acids, amines, and peptides Dale’s Principle –One neuron, one neurotransmitter Co-transmitters –Two or more transmitters released from one nerve terminal –An amino acid or amine plus a peptide
25
Neurotransmitter Chemistry Cholinergic (ACh) Neurons
26
Neurotransmitter Chemistry Cholinergic (ACh) Neurons
27
Catecholaminergic Neurons –Involved in movement, mood, attention, and visceral function –Tyrosine: Precursor for three amine neurotransmitters that contain catechol group Dopamine (DA) Norepinephrine (NE) Epinephrine (E, adrenaline)
28
Serotonergic (5-HT) Neurons –Amine neurotransmitter Derived from tryptophan –Regulates mood, emotional behavior, sleep Selective serotonin reuptake inhibitors (SSRIs) - Antidepressants –Synthesis of serotonin
29
Amino Acidergic Neurons –Differences among amino acidergic neurons quantitative NOT qualitative –Glutamic acid decarboxylase (GAD) Key enzyme in GABA synthesis Good marker for GABAergic neurons GABAergic neurons are major of synaptic inhibition in the CNS
30
Other Neurotransmitter Candidates and Intercellular Messengers –ATP: Excites neurons; Binds to purinergic receptors –Endocannabinoids –Retrograde messengers
31
Consumption of Cannabis: Effect is due to its ability to alter neural activity in the brain in ways similar to several different neurotransmitters
32
Transmitter-Gated Channels Introduction –Fast synaptic transmission –Sensitive detectors of chemicals and voltage –Regulate flow of large currents –Differentiate between similar ions The Basic Structure of Transmitter-Gated Channels –Pentamer: Five protein subunits
34
Transmitter-Gated Channels Amino Acid-Gated Channels –Glutamate-Gated Channels AMPA, NMDA, kainite
35
Transmitter-Gated Channels Amino Acid-Gated Channels –GABA-Gated and Glycine-Gated Channels GABA mediates inhibitory transmission Glycine mediates non-GABA inhibitory transmission Bind ethanol, benzodiazepines, barbiturates
36
GPCR Effector Systems –The Shortcut Pathway From receptor to G-protein to ion channel; Fast and local
37
GPCR Effector Systems –Second Messenger Cascades G-protein: Couples neurotransmitter with downstream enzyme activation
38
GPCR Effector Systems (Cont’d) Push-pull method (e.g., different G proteins or stimulate and inhibit adenylyl cyclase)
39
Divergence –One transmitter activates more than one receptor subtype greater postsynaptic response Convergence –Different transmitters converge to affect same effector system Divergence and Convergence in Neurotransmitter Systems
40
Concluding Remarks Neurotransmitters –Transmit information between neurons –Essential link between neurons and effector cells Signaling pathways –Signaling network within a neuron somewhat resembles brain’s neural network –Inputs vary temporally and spatially to increase and/or decrease drive –Delicately balanced –Signals regulate signals- drugs can shift the balance of signaling power
Similar presentations
© 2024 SlidePlayer.com Inc.
All rights reserved.