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Block 4: Unit 1D
Catecholamine Transmitters
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Undergraduate 4
12/11/2016

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Term
In the vast majority of cases, catecholamines have ______ functions
Definition
neuromodulatory
Term
5 types of monoamine transmitters
Definition
1. dopamine (DA)
2. norepinephrine (NE, AKA noradrenaline)
3. epinephrine (EPI, AKA adrenaline)
4. serotonin (5-HT)
5. histamines
Term
3 catecholamines
Definition
1. DA
2. NE
3. EPI
Term
Catecholamines work largely in a ______ fashion in the CNS
Definition
paracrine
Term
Do catecholamines have wide or small projections from the cell body?
Definition
wide
Term
When catecholamine brainstem areas become active --> ?
Definition
overall brain activity levels are affected
Term
_____ neurons act more in the periphery (not as much around the brain)
Definition
EPI
Term
Are catecholamines primarily inhibitory or excitatory?
Definition
actions are actually all over the board if they're inhibitory or excitatory
Term
NE going form locus coeruleus in the brainstem --> ?
Definition
pyramidal cells in the hippocampus
Term
5 steps of NE in the beta-adrenergic receptor in the hippocampus (responsible for a lot of the after-hyperpolarization phase of the action potential [AHP dip])
Definition
1. NE binds
2. activates adenyl cyclase
3. cAMP
4. PKA
5. affects calcium-dependent potassium channel
Term
No NE on the beta-adrenergic receptors in the hippocampus (control): continued stimulus --> ?
Definition
action potentials at a slower rate
Term
NE application on the beta-adrenergic receptors in the hippocampus: continued stimulus --> ?
Definition
much faster rate of firing of action potentials over & over again (virtually no AHP dip)
Term
Increase of locus coeruleus activity (NE) --> ?
Definition
increase of Hz of action potentials
Term
Why does application of NE to the beta-adrenergic hippocampal receptors cause a faster rate of action potential firing?
Definition
lack of AHP
Term
common precursor for all catecholamines
Definition
tyrosine
Term
4 steps to make all catecholamines
Definition
1. tyrosine --> (via TH enzyme) --> L-DOPA
2. L-DOPA --> (via AAAD enzyme) --> DA
3. DA --> (via DBH enzyme) --> NE
4. NE --> (via PNMT enzyme) --> EPI
Term
tyrosine --> (via "tyrosine hydroxylase" [TH] enzyme) --> L-DOPA

*where does this happen?*
Definition
cytoplasm
Term
Is tyrosine hydroxylase (TH) unique to catecholamine-containing neurons?
Definition
yes!
Term
What is the first unique enzyme in the catecholamine synthesis pathway?
Definition
tyrosine hydroxylase (TH)
Term
3 co-factors required for tyrosine hydroxylase (TH)
Definition
1. iron
2. VH4
3. oxygen
Term
L-DOPA --> (via AAAD enzyme) --> DA

*where does this occur?*
Definition
cytoplasm
Term
Is AAAD (aromatic amino acid decarboxylase) enzyme good for labeling DA neurons?
Definition
no! (it is a ubiquitous enzyme)
Term
How is DA packaged into vesicles?
Definition
VMAT (vesicular monoamine transporter)
Term
Where does DA --> (via dopamine beta-hydroxylase) --> NE happen?
Definition
inside of vesicle
Term
2 neurons that dopamine beta-hydroxylase is unique to
Definition
1. NE
2. EPI

*not found in DA neurons*
Term
How does NE get transported out of the vesicle to be turned into EPI?
Definition
VMAT (same transporter as with dopamine!)
Term
Where is PNMT located?
Definition
cytoplasm
Term
What determines how far along the catecholamine synthesis pathway a neuron gets?
Definition
presence of enzymes
Term
Catecholamine synthesis is regulated via a ______ feedback loop
Definition
negative
Term
Describe the negative feedback loop for catecholamine synthesis regulation
Definition
when there is a lot of one of the neurotransmitters (DA, EPI, or NE), it will feedback to the TH & downregulate its activity
Term
What experiment proved the negative feedback loop for catecholamine synthesis regulation?
Definition
1. put tyrosine & TH in a test tube --> L-DOPA
2. put tyrosine & TH & DA, NE, or EPI --> nothing!
Term
What is key for catecholamine synthesis regulation?
Definition
TH
Term
MAO
Definition
enzyme that breaks down catecholamines (monoamines)

*located both intracellularly & extracellularly*
Term
COMT
Definition
enzyme that breaks down catecholamines

*only extracellular*
Term
DAT
Definition
transporter that brings dopamine back into the presynaptic terminal
Term
NET
Definition
transporter that brings NE or EPI back into the presynaptic terminal
Term
Many inhibitors of monoamine transporters are ______ drugs
Definition
psychoactive
Term
Psychoactive drugs mainly affect catecholamine levels via ______
Definition
transporters
Term
presence of cocaine = build-up of DA in the synaptic cleft --> larger & longer-lasting DA spike

why?
Definition
cocaine blocks DAT
Term
presence of amphetamine = even bigger, longer DA spike than cocaine

why?
Definition
blocks DAT but also goes backwards through DAT to get into the presynaptic terminal to block VMAT
Term
MPTP & the frozen addicts
Definition
people coming into doctors with Parkinson's-like symptoms coming on very quickly
Term
the frozen addicts were _____ addicts
Definition
heroin (but whoever made their heroin made it wrong)
Term
MAO turns MPTP into --> ?
Definition
MPP+
Term
How quickly did the frozen addicts develop their symptoms
Definition
within days of taking the drug
Term
Parkinson's Disease is a chronic & progressive _____ disorder
Definition
CNS
Term
Parkinson's Disease primarily affects the ______
Definition
substantia nigra
Term
4 main symptoms of Parkinson's Disease
Definition
1. tremor
2. bradykinesia
3. rigidity
4. change in speech
Term
Do Parkinson's Disease treatments vary from person to person?
Definition
yes!
Term
Main goal of Parkinson's Disease treatment: ?
Definition
target DA receptors or alter the amount of DA present
Term
What is the benefit of using L-DOPA to treat Parkinson's Disease?
Definition
can cross the BBB & be converted into DA
Term
Are DA agonists as effective of a treatment for Parkinson's Disease as L-DOPA?
Definition
no but the effects last longer
Term
2 enzymes inhibited in Parkinson's Disease treatment
Definition
1. MAO
2. COMT
Term
What do anticholinergics do to treat Parkinson's Disease?
Definition
block mAChR to stop resting tremor
Term
What does dopamine do in the motor signaling?
Definition
modify the synapses
Term
About _____% of Parkinson's patients develop the disease due to treatment with a specific medication
Definition
7%
Term
impulsivity disorders
Definition
get urge to do normal human behavior but do it in excess
Term
Do people with impulsivity disorders know that what they're doing is wrong?
Definition
yes, but they still do it anyway
Term
impulse control disorders (ICDs)
Definition
behavioral disturbance resulting from the failure to resist the drive to behave in ways that result in distress or impaired social & occupational functioning
Term
What is the main treatment for impulsivity disorders?
Definition
reduce or stop using the suspected agent (especially DA agonists)
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