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Neuro Pharmacology > Nicotinics & AChE > Flashcards

Nicotinics & AChE Flashcards

1
Q

What kind of receptors are Nicotinic Cholinergic Receptors (nAChRs)?

A

LGIC’s (Na+, Ca2+)

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2
Q

In the somatic nervous system, what is the structure of nAChRs?

A

They are a Pentameric Structure.

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3
Q

In the somatic nervous system where are the ACh binding sites located on the nAChRs?

A

Alpha interface

Delta/Epsilon interface.

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4
Q

How many ACh molecules must bind to open the ion channel?

A

2

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5
Q

What kind of nAChRs are located in the the Autonomic ganglia/Adrenal Medulla?

A

Alpha 3 containing.

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6
Q

What kind of isoforms of nAChRs exist in the CNS?

A

Many receptor isoforms BUT alpha and beta subunits only.

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7
Q

What is the most common alpha subunit in the CNS?

A

Alpha 4.

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8
Q

Which alpha subunit of nAChRs has high levels of expression in brain DA neurons?

A

Alpha 6

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9
Q

What is the second most common alpha subunit of nAChRs?

A

Alpha 7

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10
Q

What is the alpha 7 subunit of nAChRs more permeable to?

A

Increase Ca2+ permeability.

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11
Q

What alpha subunit of nAChRs is only expressed in the cochlea?

A

Alpha 9

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12
Q

What are the Direct Acting Nicotinic Agonists?

A
  1. Nicotine
  2. Lobeline (indian tobacco)
  3. Epibatidine (frog)
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13
Q

Why are actions of nicotinic agonists complex?

A
  1. Many potential sites of action.
  2. Activation of receptors followed by prolonged desensitization
  3. Nicotine a “secretagoge” - nAChRs on many types of presynaptic nerve terminals.
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14
Q

What are the most common exposures that cause acute nicotine toxicity?

A
  1. Pesticides
  2. Children eat cigs
  3. Harvesting tobacco
  4. Smoking while using nicotine patch or ecig
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15
Q

What can happen at a level of 40mg of nicotine?

A

Death due to:

  1. convulsions
  2. myocardial infarction
  3. Respiratory failure.
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16
Q

How do you treat nicotine overexposure?

A
  1. Gastric lavage

2. Mecamylamine for convulsions

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17
Q

What are symptoms of nicotine withdrawal?

A
  1. Dizziness, Tremor, High BP
  2. irritability, craving, anxiety, restlessness, difficulty concentrating.
  3. IBS and increased appetite.
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18
Q

What are pharmacological tools for smoking cessation?

A
  1. NRT
  2. Verenicline (chantix) - partial agonist
  3. Bupropion
  4. Clonidine
  5. NicVax?
  6. BMOD
  7. Ecig?
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19
Q

Does a nicotinic agonist or antagonist increase the number of receptors?

A

BOTH can.

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20
Q

Where are Neuronal nictotinic receptors prominently located?

A

On the presynaptic nerve terminals.

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21
Q

What does nicotine reinforce?

A

Voluntary inhalation of known carcinogens.

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22
Q

What are Therapeutic actions of nicotinic agonists?

A
  1. Parkinson’s
  2. Alzheimer’s
  3. Cognitive disorders
  4. Schizophrenia/ADHD
  5. Tourette’s
  6. Ulcerative colitus
  7. Anxiety/ Alcholoism
  8. Analgesia
  9. Obesity
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23
Q

How do indirect acting skeletal muscle relaxants work?

A

By decreasing ACh release in somatic NS.

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24
Q

How do direct acting skeletal muscle relaxants work?

A

Block muscle nAChRs
aka Paralytic drugs

Can be competitive and non-competitive.

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25
Q

Do skeletal muscle relaxants affect the CNS or cross the placenta?

A

NO

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26
Q

How to non-depolarizing neuromuscular competitive antagonists work?

A

Block agonist recognition site on alpha subunit.

27
Q

When using a non-depolarizing neuromuscular blocker, when will you see a effect?

A

when 75-80% of nAChRs are blocked.

28
Q

Non-depolarizing neuromuscular blockers can produce ganglionic blockade, what does that cause?

A

Hypotension

Reflex tachycardia.

29
Q

How is the effect of non-depolarizing neuromuscular blockers typically reversed?

A

with AChEIs

30
Q

Agonist binding to Nicotinic ACh receptors causes the channel to do what?

A

Block sodium influx into the cell.

31
Q

What is an example of depolarizing neuromuscular blockers?

A

Succinylcholine

32
Q

How does succinylcholine work?

A

Depolarizes the NMJ initially, then produces a longer lasting blockade of the ion channel.

33
Q

What does succinylcholine have affinity for?

A
  1. Agonist recognition site - competitive (brief)

2. Central ion channel - non-competitive (prolonged)

34
Q

Does succinylcholine invoke local histamine release?

A

NO it does not, it is a non-irritant.

35
Q

What is succinylcholine metabolized by?

A

Plasma cholinesterase ( + for rapid procedures; butyrl)

36
Q

what is blocked in phase 1 block of the NAChR?

A

The allosteric site where nicotine normally binds.

37
Q

What is blocked in phase 2 block of the NAChR?

A

The actual channel.

38
Q

What are adverse drug reactions of succinylcholine?

A
  1. Postoperative muscle pain.
  2. Hyperkalemia
  3. Malignant hyperthermia
39
Q

What kind of drug is Mecamylamine?

A

Ganglionic Blocking Drug.

40
Q

What do ganglionic blocking drugs cause?

A
  1. Decreased BP
  2. Loss of CV reflexes
  3. Severe orthostatic hypotension –>sncope
  4. Constipation, urinary retention, dry mouth, cycloplegia
  5. Ganglionic blockade causes PARTIAL mydriasis
41
Q

What are ganglionic blocking drugs in clinical trials for?

A

Anti-Depressant.

42
Q

What are therapeutic uses of Acetylcholinesterases (AChE)?

A
  1. Recovery from COMPETITIVE NMJ blockers
  2. Autoimmune myasthenia gravis
  3. Atropine (or scopolamine) poisoning.
  4. Tricyclic anti-depressant overdose
  5. Cognitive improvement in dementia.
43
Q

When does acetylcholinesterase act as a high efficacy enzyme?

A

when in high abundance.

44
Q

What is a acetylcholinesterase?

A

A serine hydrolase located on the outer cell membrane of neurons (pre & postsynaptic) in the CNS & PNS.

A globular protein w/ active center buried in interior.

45
Q

What is the concentration of AChE at synapses?

A

10-20X greater than that needed to activate ACh.

46
Q

How fast can a single active enzyme of AChE hydrolyze ACh?

A

10,000 molecules/ second.

47
Q

What is Butyrlcholinesterase important for?

A

Catabolism of:

  1. Some xenobiotics
  2. Inhalation anesthetics
  3. Succinylcholine
  4. Cocaine
48
Q

What Carbamates cross the BBB?

A

Donepezil

Galanthamine (also a nAChR APL)

49
Q

What Carbamates dont cross the BBB?

A

Pyridostigmine (MG, prophylaxis in PGW)

50
Q

What are Carbamates?

A

Acetylcholine esterase inhibitors.

51
Q

How are ADRs of AChEI’s caused?

A

Indirect agonism of nicotinic and muscarinic cholinergic receptors (ANS + Somatic + CNS)

52
Q

What is Myasthenia Gravis and what does it cause?

A

An Autoimmune disorder that affects the NMJ.

Causes grave muscular weakness.

53
Q

How is Myasthenia Gravis treated?

A

With AChEIs, Corticosteroids, plasma pharesis, thymectomy.

54
Q

What is Lambert Eaton Myasthenic Syndrome?

A
  1. AB’s to Ca2+ channels.
55
Q

What are Organophophates?

A

Irreversible Inhibitors of AChE –> nerve gas.

56
Q

What are the 4 nerve gases?

A

Tabun (GA)
Sarin (GB) highly volatile
Soman (GD) Viscous
VX Stable

57
Q

What are the stages of OP Inhibition of AChE?

A
  1. Formation of the Michaelis enzyme-substrate complex.
  2. Phosphorylation of the enzyme on a serine residue.
  3. “aging” of the complex is due to the attachment of a charged monophosphate group.
58
Q

What needs to be synthesized because the endogenous reactivation of the AChE enzyme is so slow?

A

A new enzyme to re-initiate AChE activity.

59
Q

What does OP poisoning cause?

A
  1. Acute Cholinergic Crisis

2. Activates CNS, SNS, PNS, Somatic NS.

60
Q

What are physiological things that happen from OP poisoning?

A
  1. Miosis
  2. Lacrimation
  3. Bradycardia
  4. Vomiting
  5. Confusion
  6. Convulsions
  7. Sweating
  8. Increased secretions
  9. Neuromuscular weakness
  10. Bronchoconstriction
  11. loss of sphincter control
  12. anxiety
61
Q

What are usually the first signs of OP exposure?

A

Eye and Respiratory irritation.

62
Q

What are the most severe manifestations of OP exposure?

A
  1. Bronchial constriction
  2. Increased pulmonary secretions
  3. Paralysis of the diaphragm and respiratory muscles.
  4. Paralysis of the respiratory control center in CNS.
63
Q

What is the Treatment of OP Poisoning?

A
  1. Immediate supportive measures
    - termination of exposure, gastric lavage, 100%O2, mechanical ventilation.
  2. Atropine to block muscarinic post-synpatic responses.
  3. Oximes
    - nucleophilic agents, 2PAM facilitate reactivation of enzyme. Must be before “aging”
  4. Anticonvulsants
    - BZ’s decrease anxiety and convulsions.

Neuro Pharmacology (9 decks)

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