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121 > Module 2D (Pt4) > Flashcards

Module 2D (Pt4) Flashcards

1
Q

What transmitters does adrenergic transmission consist of

A
  • Norepinephrine (NE)
    • Epinephrine
    • Dopamine
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2
Q

What is norepinephrine

A
  • Main transmitter of SNS post ganglionic gibers
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3
Q

What is epinephrine

A
  • The major hormone of the adrenal medula
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4
Q

What is dopamine

A
  • Main transmitter of other systems and pathways but we don’t learn them
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5
Q

What is the main neurotransmitter of the SNS

A
  • Norepinephrine
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6
Q

What are the different catecholamines

A
  • Norepinephrine
    - Epinephrine
    - dopamine
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7
Q

Catecholamines actions have therapeutic utility for what

A
  • Hypertension
    • Mental disorders
    • Bronchospasm
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8
Q

Catecholamines actions have therapeutic utility for what

A
  • Hypertension
    • Mental disorders
    • Bronchospasm
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9
Q

What are the parts of adrenergic transmission

A

i) Catecholamine synthesis
ii) Storage
iii) Release
iv) regulation
v) uptake
vi) Termination of release

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10
Q

Explain catecholamine synthesis

A

i) tyrosine is transported into the cell
ii) Tyrosine is converted to dopa by TH (tyrosine hydroxylase)
iii) DDOPA converted to dopamine by aromatic L- amino acid decarboxylase (AAADC)
iv) Dopamine transported into vescles by VMAT2
v) Dopamine converted to NE by Bopamine B- Hydroylase (DBH)
vi) NE converted to epinephrine by PNMT (phenylethanolamine-N-Methyl transferase in chromaffin cells of the adrenal medula

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11
Q

Is dopa the same as dopamine

A
  • No but DOPA is converted into dopamine
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12
Q

What enzyme converts DOPA into dopamine

A
  • Amino acid decarboxylase (AAADC)
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13
Q

What gets converted to DOPA by TH

A
  • Tyrosine
    • TH is tyrosine hydroxylase
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14
Q

What is the rate limiting step in catecholamine synthesis

A
  • Second step
    • Tyrosine is converted to dopa by TH (tyrosine hydroxylase)
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15
Q

Where is NE converted into epinephrine

A
  • In chromaffin cells of adrenal medula
    • Converted by PNMT
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16
Q

What are the parts of catecholamine storage

A

Uses Vesicular Monoamine transporter 2 (VMAT2)
i) Ph dependent pump
- Exchanges 2 H+ for one catecholamine

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17
Q

What inhibits VMAT2

A
  • Reserpine
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18
Q

What was reserpine historically used for

A
  • Hypertension, psychosis, dyskinesia in Huntington’s
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19
Q

Why is reserpine not used anymore

A

This is as it inhibits all VMAT2 as it is not specific

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20
Q

What does TH deficient humans have

A
  • Rigidity and hypokinesia
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21
Q

What does DBH deficiency cause in humans

A

Orthostatic hypotension

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22
Q

Catecholamine uptake

A
  • Mediated by Norepinephrine Transporter (NET)
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23
Q

What percent of NE will be uptaken or recycled and by what

A
  • About 87%
    • Recycled by NET
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24
Q

What is the Na+ dependent reuptake pump inhibited by and what occurs if it is

A
  • Tricyclic antidepressants (TCA) and cocaine
    • This makes NE (and other catecholamines) be help in the synaptic cleft where they can continue to do there job
    • Sympathetic nervous system on overdrive (super stimulated)
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25
Q

What is the specificity of NET for the different catcholamines

A
  • Dopamine > NE > epinephrine
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26
Q

What inhibits or reverses NET and VMATs and what does this mean

A
  • Methamphetamines
    • This means that NET isn’t only being blocked by it also pumps catecholamines into the synaptic cleft also so ever greater activation of SNS
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27
Q

Catecholamine release (release of NE)

A
  • When an axon terminal depolarizes
    i) Voltage gates Ca channels open
    ii) Ca allows for interactions between VAMPs/ SNAPs and vesicles/ membranes
    iii) Membrane fusion occurs allowing NE to exit the cell by exocytosis
28
Q

What are the SNAREs

A
  • VAMPs and SNAPs
29
Q

Is the release of NE the same process of Ach release

A
  • Essentially yes
30
Q

How does NE exit the cell

A
  • Exocytosis
31
Q

What happens when N-type Ca channels are inhibited

A
  • Hypotension due to decreased NE
32
Q

Regulation of NE release

A
  • By autoreceptors
33
Q

What is an autoreceptor

A
  • A receptor present on the same cell as the released transmitter
34
Q

What do a2A, a2B, a2C adrenergic receptors do

A
  • Inhibit NE release
    • Through a negative feedback loop
35
Q

What do B2 adrenergic receptors do

A
  • Enhance NE release
    • Through a positive feedback loop
36
Q

Termination of NE release

A
  • Mediated by MAO (monoamine oxidase) and COMT (catechol-O-methyltransferase)
    When the NE is taken up MAO and COMT go to work
37
Q

Difference between MAO and COMT

A
  • COMT is not associated within the SNS
    • Sympathetic nerves have MAO but not COMT
38
Q

What do MAO and COMT do

A
  • Stop the release of NE
39
Q

What are inhibitors of MAO and CMT useful for

A
  • CNS effects (depression, parkinsons)
    • Have few peripheral effects
40
Q

True of false: cocaine is a stimulant of the SNS

A
  • True
    • Cocaine inhibits NET, so keeps the NE in the synaptic cleft so is a stimulant, this causes the SNS to be exacerbated
41
Q

What do a receptors do

A
  • Alpha
    • Smooth muscle cells of organs and blood vessels around organs
    • NE binds and causes contriction which means less blood flow
42
Q

What do B receptors do

A
  • Beta
    • Heart and blood vessels around lung and muscle
    • NE binds and causes relaxation meaning more blood flow
43
Q

What are the Gq coupled GPCRs

A

a1A,B,D

44
Q

What do Gq- coupled GPCRs do

A
  • Activates the G protein, calcium release and contraction
45
Q

What are the Gi- coupled receptors

A
  • A 2A,B,C
46
Q

What do the Gi coupled GPCRs do

A
  • I= inhibit
    • ATP decreases, K channels activated, Ca channels inhibited
      • Causes hyperpolarization
47
Q

What are the Gs coupled GPCRs

A
  • B1,2,3
48
Q

What do the Gs- coupled GPCRs do

A
  • Stimulate; opposite of gi
    - Camp increases, K channels inhibited, Ca channels activated
    - Increase in excitability and contraction
    - Present in heart and blood vessels of lungs
49
Q

Other names for desensitization

A
  • Refractoriness
    • Tachyphylaxis
50
Q

What is Desensitization

A
  • a progressive diminished response due to repeated exposure of catecholamine sensitive tissue to agonists
51
Q

What are the causes of desensitization

A
  • GRKs (G protein receptor kinases)
    • Barrestins
    • Receptor sequestration
    • Endocytosis
52
Q

When desensitization occurs what do you need to do with drug dosing

A
  • Need a larger dose of the drug to cause the same response
    • Can cause more adverse effects
53
Q

If you have a drug that was an agonist (causes a response)of beta receptors what is the effect on the heart

A
  • Contraction, force and heart rate will go up
54
Q

What are sympathomimetics

A
  • Adrenergic agonists
55
Q

What are organ effects from sympathomimetics (eye, lung, Genitourinary tract, vascular system, Heart, metabolic)

A

i) Eye
- Decrease intraocular pressure through mydriasis (a1 agonists: phenylephrine)
- Decrease intraocular pressure through aqueous humor (a2 agonists)
ii) Lung
- can treat bronchospasm (asthma) through B2 agonists (isoproterenol, albuterol)
iii) Genitourinary tract
- Increase sphincter tone in bladder through a1 agonists
iv) Vascular system
- Increase blood pressure through reflex bradycardia (a1 agonists)
- Increase bp i.v. or topically (a2 agonists: clonidine)
- Decrease bp in skeletel muscle arterioles (B2 agonists)
v) Heart (B1, B2 receptors)
- Increase cardiac pacemaker rate
- Increase atrioventricular node conduction
- Increase cardiac force
vi) Metabolic
- Increase renin secretion (B1 agonists)
- Increase insulin secretion, glycogenolysis (in liver) (B2 agonists)

56
Q

What is the baroreceptor reflex

A
  • A homeostatic response to maintain blood pressure through sensing pressure changes and response to change in tension of the arterial wall
57
Q

Steps of the baroreceptor reflex

A

i) NE: a and B agonist
ii) A increase blood pressure and B increase Heart rate
iii) The increase bp triggers the vagus nerve which then decreases heart rate (vagal reflex arc)

58
Q

What is the difference between specific and non specific agonists (NE vs isoproterenol)

A

i) NE
- Agonist of a and B receptors
- Cause an increase in both systolic and diastolic BP
- The a increases blood pressure (constrict certain blood vessels)
- The B increase Heart rate
- The increase in BP triggers the Vagus nerve and this decreases heart rate ( Vagal reflex arc)
- This means get an increase in bp and decrease in heart rate
ii) Isoproterenol
- Selective with B receptors
- Causes a huge increase in heart rate but the bp only briefly goes up but then goes down as the a receptors arent being activated

59
Q

What is isoproterenol and what does it do

A
  • A B1,2 agonist
    • Increase heart rate and decrease bp by vasodilation in skeletal muscle
60
Q

Adrenergic agonist clinical utility

A
  1. Anaphylaxis
    • Hypotension, bronchospasm, angioedema
    • Example: epinephrine
      2. Allergy and glaucoma
    • Itching, miosis, Intra ocular pressure
    • Example: phenylephrine (a), brimonidine (a2)
      3. Acuta astham
    • Bronchospasm and constriction
    • Example: albuterol (B2)
      4. Heart failure and shock
    • Increase blood flow
    • NE
      5. Decongestant
    • Decrease blood flow
    • Phenylephrine, ephedrine (a)
      6. Cardiac stimulation and AV block
    • Epinephrine
      7. urinary incontinence
    • Ephedrine
61
Q

Do selective agonists bind to other receptors

A
  • Yes nothing is perfectly selective
    • At high enough dose there will be non specific side effects
    • B1: can cause tachycardia, arrhythmia
    • a1: hypertension
    • B2: skeletal muscle tremor
62
Q

Adrenergic antagonist utility

A
  • Anywhere we want to block the SNS activity
    i) Non selective B
    • Acute angle closure glaucoma (timolol), local anesthetics and anxiety
      ii) B1
    • Hypertension, angina, arrhythmia, heart failure
      iii) Nonselective a
    • Pheochromocytoma
      iv) a1
    • Usually end in osin
    • Hypertension, urinary retention
      v) a2
    • Reversal of sedation
63
Q

What do B adrenergic antagonists usually end in

A
  • Olol
64
Q

What causes adrenergic antagonist toxicity

A
  • A natural extension of their pharmacological actions
65
Q

What happens when we use adrenergic antagonists

A
  • If we block the SNS we allow the PNS to go up
66
Q

Examples of adrenergic antagonist toxicity

A
  • Bradycardia
    • Atrioventricular blockade
    • Heart failure
    • Asthma attacks
    • Sexual dysfunction
67
Q

What does it mean when B-blockers start with a-m (excluding c)

A

They are B1 selective

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