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Block 4: Unit 1C
Glutamate, Glycine, & GABA
51
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Undergraduate 4
12/11/2016

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Term
Why is understanding how a neurotransmitter is made useful?
Definition
it can help you create pharmacological treatments that either enhance or slow down the synthesis of that specific transmitter
Term
2 pathways for glutamate synthesis
Definition
1. alpha-ketoglutarate --> (via glutamate dehydrogenase) --> glutamate
2. glutamine --> (via glutaminase) --> glutamate
Term
Is glutamate a specific identifier for glutamatergic neurons?
Definition
no! (glutamate is everywhere)
Term
Can glutamate cross the BBB?
Definition
no! (it is negatively charged)
Term
2 requirements for glutamate to get packaged into vesicle
Definition
1. VGLUT (vesicular glutamate transporter)
2. vesicular proton pump (ATPase pump that pumps one proton in)
Term
How do you identify the action of glutamate in a neuron?
Definition
1. stimulate presynaptic neuron --> you get an EPSP
2. puff glutamate onto synapse without stimulating presynaptic neuron --> EPSP
Term
Why do you need glutamate reuptake?
Definition
so synapse can be ready for the next time a signal comes through
Term
What is the goal of glutamate reuptake?
Definition
termination of action via taking out/degrading neurotransmitter
Term
______ bring glutamate right back up into the presynaptic terminal
Definition
glutamate transporters
Term
In the CSF (fluid around neurons & in synapse), there is typically ______ of glutamate
Definition
1 micromolar (remember it is ubiquitous & everywhere)
Term
What is the role of glial cells in glutamate reuptake?
Definition
they kind of isolate the synapse (block on either side)
Term
Once glutamate is in the cell, this reaction happens: ?
Definition
glutamate --> (via glutamine synthetase) --> glutamine
Term
Once glutamate is back in the presynaptic terminal, _____ works to package it back into vesicles for release
Definition
VGLUT
Term
AMPAR desensitization
Definition
conformational change to an inactive state
Term
AMPA receptors desensitize at a rate of ______
Definition
10's of milliseconds (really fast!!)
Term
blocking AMPAR desensitization --> what happens to the current trace?
Definition
you get a much wider current trace (takes curve longer to inactivate)
Term
Do NMDA receptors take less, longer, or about the same amount of time to inactivate as to AMPA receptors?
Definition
they have a much longer time it takes them to desensitize
Term
Is glycine associated more with inhibitory or excitatory?
Definition
inhibitory
Term
2 places where glycine is largely found
Definition
1. retina
2. spinal cord
Term
_____ is a co-agonist for NMDA glutamate receptors (where glutamate binds so sodium & calcium can go in & potassium can go out)
Definition
glycine (there is a separate glycine binding site)
Term
Glycine binding ______ glutamate binding to its site on an NMDAR
Definition
facilitates/potentiates
Term
Why don't we know the result of having a lack of glycine at NMDARs?
Definition
glycine is so common
Term
Why is glycine called a "co-agonist" for NMDARs?
Definition
it isn't truly an agonist but it helps glutamate binding so much
Term
glycine synthesis
Definition
serine --> (via serine-trans-hydroxymethyl-transferase) --> glycine
Term
glycine uses _____ to be packaged into vesicles
Definition
VGAT
Term
stimulating the presynaptic terminal of a glycinergic neuron OR puffing glycine onto the synapse --> ?
Definition
IPSP
Term
2 ways for glycine reuptake
Definition
1. GLYT-2 found in presynaptic neurons
2. GLYT-1 found in glial cells
Term
What is the main inhibitory neurotransmitter in the CNS?
Definition
GABA
Term
Are there many or only a few GABAergic synapses?
Definition
many
Term
GABA synthesis
Definition
glutamate --> (via glutamic acid decarboxylase [GAD]) --> GABA
Term
how do you get GABA into a vesicle?
Definition
VGAT
Term
stimulation & application of GABA to a synapse --> ?
Definition
IPSP
Term
2 ways for GABA reuptake
Definition
1. GABA-T found in presynaptic neurons & glia
2. GAT found in presynaptic neurons & glia
Term
Schizophrenia seems to arise from an issue with _____ connections
Definition
GABAergic
Term
epilepsy
Definition
a neurological disorder characterized by sudden recurrent episodes of sensory disturbance, loss of consciousness, and/or convulsions, associated with abnormal, excessive neuronal activity in the brain
Term
3 causes for epilepsy
Definition
1. disruptions in neuronal connectivity that lead to excessive excitation or insufficient inhibition
2. damage to brain tissue
3. genetic or developmental abnormalities that prevent normal neuronal connectivity
Term
4 epilepsy treatments
Definition
1. medications
2. Neurostimulation
3. dietary approach
4. surgery to remove brain tissue that starts seizures
Term
Only _____% of epilepsy patients get sufficient seizure control with current treatment options
Definition
60-70
Term
Anti-seizure drugs that modify voltage-gated ion channels --> ?
Definition
inhibit sodium & calcium channels
Term
Anti-seizure drugs that enhance synaptic inhibition --> ?
Definition
increase GABA activity
Term
Anti-seizure drugs that inhibit synaptic excitement --> ?
Definition
decrease glutamate activity
Term
Gabapentin is a drug that is structurally similar to ______
Definition
GABA
Term
Gabapentin binds to a subunit on _____ channels --> regulate channel activity (prevents it from opening as frequently)
Definition
calcium
Term
Gabapentin modulates the action of GAD --> ?
Definition
increase GABA synthesis
Term
Gabapentin stimulates noradrenaline mediated descending inhibition --> ?
Definition
anti-hypersensitivity in neuropathic pain
Term
topiramate
Definition
drug that basically works to either decrease excitability or increase inhibition
Term
topiramate blocking sodium channels --> ?
Definition
stabilize inactive form of the channel
Term
topiramate GABA receptor facilitator --> ?
Definition
inhibits the neuron
Term
What causes the side effects of antiepileptic drugs?
Definition
non-specific actions of the drugs
Term
5 unintended effects of antiepileptic drugs
Definition
1. weight gain
2. liver failure
3. loss of hair
4. depression
5. headaches
Term
Why do antiepileptic drugs get abused?
Definition
users say it gives them a marijuana-like sense of calmness/relaxation
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