Neurotransmitters and Receptors Flashcards
Give a general description of neurotransmitters
- What cells synthesizes NT?
- Where and how are they stored?
- What causes the release of NT?
- What do NT do when released?
- Synthesized by neurons
- Stored in vesicles at nerve terminals
- They are released, after depolarization, into the synaptic cleft
- They bind to a receptor and cause a conformational change, which results in altered physiology or chemistry in the post-synaptic cell
What are the five classes of neurotransmitters?
- Monoamines
- Cholinergic
- Amino ccids
- Neuropeptides
- Nontraditional neurotransmitters
What neurotransmitters are monoamine class?
Catecholamines
- Norepinephrine (noradrenalin)
- Epinephrine
- Dopamine
Serotonin
What neurotransmitter is cholinergic class?
Acetylcholine
What neurotransmitters are amino acid class?
- GABA - gamma-aminobutyric acid
- Glycine
- Glutamate and other excitatory amino acids
What neurotransmitters are neuropeptide class?
How do their number of amino acids in neuropeptides compare to proteins? What do neuropeptides do?
Dozens, including endorphins, calcitonin gene-related peptide, and substance P.
They contain a fewer # of amino acids than proteins. They modulate synaptic transmission.
What neurotransmitters are non-traditional class?
NO and CO2
They can be substances that diffuse generally across the synapse.
What generalization can be made about NT’s that open Na+ channels and those that open Cl- channels?
Open Na+ : excitatory (EPSP’s)
Open Cl- : inhibitory (IPSP’s)
What are the targets for most pharmacological interventions in the nervous system?
Neurotransmitters and their receptors
What are the two broad classes of neurotransmitter receptors?
Ionotropic receptors
Metabotropic receptors (aka G-Protein coupled receptors)
What happens when a NT binds to an ionotropic receptor?
When a NT binds to a ionotropic receptor a conformational change in the transmembrane proteins occurs, which opens an ion channel.
This can cause a local depolarization or hyperpolarization of the membrane (EPSP or IPSP).
What happens when a NT binds to a metabotropic receptor (G-protein coupled receptor)?
When a NT’s bind to receptors, a conformational change occurs which alters its G-protein, which leads to downstream effects.
What are the three possible downstream effects of an activated G-protein coupled receptor?
- Opening of ion channels (EPSP / IPSP)
- Activation of genes (which increases the rate of synthesis of specific cellular products)
- Modulation of calcium levels inside cell (which affects cell metabolism and other processes)
What ultimately determines if a neurotransmitter is excitatory or inhibitory?
The post-synaptic receptor determines if a neurotransmitter is of excitatory or inhibitory nature. Neurotransmitters can have multiple receptors with different actions.
Acetylecholine (Ach)
- Class of NT
- Location?
- Cholinergic class
- Located throughout PNS and CNS
Acetylecholine (Ach)
- Receptors and action
- Action termination
Receptors:
- Ionto R - EPSP
- Metabo R - EPSP or IPSP
Action:
- Responsible for excitatory neurotransmission at NMJ (neuromuscular junction). Regulates autonomic nervous system
Termination:
- Terminates via removal from synaptic cleft by enzymatic destruction (acetylcholinesterase)
Norepinephrine (Noradrenaline)
- Class
- Location
- Catecholaminergic class
- Location: Sympathetic ganglia, locus ceruleus, lateral tegmental nuclei
- Axons project to CNS regions
Norepinephrine (Noradrenaline)
- Receptors and action
- Action termination
- Metabo R: EPSP or IPSP
- Terminates via reuptake (presynaptic and glial), enzymatic degradation, and passive diffusion
Dopamine
- Class
- Location
- Catecholaminergic class
- Location at basal ganglia (substantia nigra), hypothalamus, ventral tegmental area
Dopamine
- Receptors and action
- Action termination
- Metabo R: Inhibitory (for most part)
- Terminates via reuptake, enzymatic degradation, and passive diffusion
Serotonin
- Class
- Location
- Monoaminergic class
- parasympathetic neurons, pineal gland, raphe nucleus
Serotonin
- Receptors and action
- Action termination
- Ionto R: EPSP
- Metabo R: EPSP or IPSP
- Terminates via reuptake
Glutamate
- Class
- Location
- Amino acid class
- Mammalian CNS (cortex, cerebellum, brainstem, hippocampus, spinal cord)
Glutamate
- Receptors and action
- Action termination
- Ionoto: EPSP
- Metabo: EPSP
(Note that Glutamate is only excitatory) - Terminates via reuptake and diffusion
GABA (Gamma-aminobutyric acid)
- Class
- Location
- Amino acid class
- Cortex, cerebellum, hippocampus
GABA (Gamma-aminobutyric acid)
- Receptors and action
- Action termination
- Ionto - IPSP
- Metabo - IPSP
(Note that GABA is purely inhibitory) - Terminates via reuptake (neurons and glia)
