E3 Amino Acid Neurotransmitters Flashcards
T/F: amino acid neurotransmitters are the most prevalent neurotransmitter in the CNS
true
what are the two major classes of amino acid neurotransmitters?
excitatory amino acid and inhibitory amino acids
what are the two excitatory amino acids?
glutamate and aspartate
what are the two inhibitory amino acids?
GABA and glycine
Is glutamate ionotropic or metabotropic?
mostly ionotropic but have some degree of metabotropic binding?
What does ionotropic mean?
membrane-bound receptor proteins that respond to ligand binding by opening an ion channel and allowing ions to flow into the cell
what does metabotropic mean?
indirectly linked with ion channels on the plasma membrane of the cell through signal transduction mechanisms (g-protein)
what are the two receptors associated with glutamate?
AMPA and NMDA
what is NMDA associated with?
excitotoxicity (overproduction can cause neuronal damage)
what does the cooperation of AMPA and NMDA receptors lead to?
long-term potentiation (long-term synaptic plasticity)
what is long-term synaptic plasticity associated with?
long-term learning
what does frequent activity across a synapse cause?
lasting changes in strength of signaling (enhancement of neuroplasticity)
What is neuroplasticity?
the ability of the nervous system to change in response to experience or the environment
In the activation of glutamate receptors, what does AMPA require to open its ion channel?
the binding of glutamate
what does the activation of AMPA lead to?
membrane depolarization and excitatory transmission
In the activation of glutamate receptors, what needs to bind to NMDA?
both glutamate and glycine (they bind to diff. sites)
what is the ion channel of NMDA blocked by?
Magnesium
what displaces the magnesium cork from NMDA?
depolarization by the activation of AMPA receptor displaces the magnesium cork
what occurs when the magnesium cork is displaced from NMDA
-opening of NMDA ion channel
-Ca2+ influx (contributes to long-term potentiation)
can glutamate pas through the BBB?
no - must be synthesized in the brain
what is glutamate synthesized from
alpha ketogluterate
what does glutamates interaction with the excitatory receptors cause?
a greater chance that an action potential will be fired
how does glutamate increase the change of an action potential being fired?
when glutamate binds to the receptors and the ion channels open the influx of Na+ causes depolarization
what are the metabotropic effects of glutamate?
glutamate is removed from the synaptic cleft by exciatory amino acid transporters (EAATS)
What do EAATs do?
carry glutamate into glial cells
what occurs to glutamate in the glial cells?
-converted to glutamine by glutamine synthetase
what occurs to glutamate after it has been converted to glutamine?
transporter back into neurons where it is converted back into glutamine
what is the process of converting glutamate into glutamine back into glutamate called?
glutamate/glutamine cycle
what are the steps of glutamate receptor activation?
- action potential into presynaptic cell
- glutamate release (Ca2+ mediated exocytosis)
- glutamate binds to both channels
- Na+ influx (depolarization)
- depolarization drives Mg2+ ion out of pore
- Ca2+ activates 2nd messenger system
- long-lasting increase in glutamate receptors and sensitivity
what are the two inhibitory amino acids?
GABA and glycine
what is GABA modified from?
glutamate (decarboxlyzed from glutamate to GABA)
where is GABA located?
interneurons that dampen circuits (synapses in CNS)
What forms of GABA are ionotropic?
GABA(A) and GABA(C)
what is the direct ionotropic effect of GABA
GABA binds to the receptors on a neuron and causes the opening of Cl- channels (hyperpolarization)
what is the indirect ionotropic effect of GABA?
opening of K+ channels or blocking of Ca2+
what form of GABA is metabotropic?
GABA(B) - g-protein linked (open close channels via intermediates)
what are the metabotropic effects of GABA
-indirect g-protein linked opening of K+ channels or blocking of Ca2+ channels
what occurs when GABA interacts with receptors of a neuron?
makes the neuron less likely to fire and action potential or release neurotransmitters
how is GABA terminated
GABA transporters transport GABA from synaptic cleft into neurons or glial cells where it is degraded by mitochondrial enzymes
what does increased GABA activity cause?
sedative effects
what increases the activity of the GABA receptor?
alcohol and benzodiazepines
Where is glycine located?
spinal cord and brain stem (not in cerebral hemispheres)
is glycine ionotropic or metobotropic?
ionotropic (chloride influx)
what is glycine synthesized from?
serine
how is glycine synthesized?
serine-hydroymethyltransferase converts serine to glycine
what is the vesicular GABA transporter used for in glycine inhibition?
glycine is transported into vesicles where it is stored
what are the steps of the glycine inhibitory pathway?
- Ca2+ enters the presynaptic cell
- Ca 2+ mediated exocytosis of glycine
- glycine binds to ligand-gated Cl- receptor
- influx of Cl- causes hyperpolarization
- glycine is removed from synapse through the glycine reuptake channel and recycled
