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LCRS - pharma > Cholinometics > Flashcards

Cholinometics Flashcards

1
Q

What are cholinomimetic drugs?

A

Drugs that mimic the action of ACh in the nervous system

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2
Q

Diagram showing synthesis, release and metabolism of ACh.

Outline the stages of neurotransmitter action (numbered 1-4)

A
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3
Q

What are muscarinic effects and how can they be abolished?

A

Effects that can be replicated by muscarine. Abolioshed by antagonist atropine.

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4
Q

What branch of the ANS are muscarinic acitons related to?

A

Parasympathetic stimulation.

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5
Q

How can nicotinic effects be induced by atropine?

A

atropine blockade of muscarinic receptors allow large doses of ACh to induce nicotinic effects.

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6
Q

How do PNS and SNS fibres differ?

A

PNS - long pre-ganglionic, ACh pre-ganglionic and post-ganglionic.
SNS - short pre-ganglionic, ACh pre-ganglionic, NA post-ganglionic.

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7
Q

Outline 2 unique SNS effector routes.

A

Adrenal medulla releasing Adrenaline and NA as neurohormones into the blood stream.

Ach post-ganglionic neurotransmitter to sweat glands instead of NA.

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8
Q

What neurotransmitter do motor neurones to skeletal muscle use?

A

Ach

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9
Q

Where are muscariniuc receptors located?

A

Post-ganglionic ACh receptors in PNS effector organs (including sweat glands)

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10
Q

Where are nicotinic Ach receptors found?

A

PNS and SNS pre-ganglionic receptors.

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11
Q

How many muscarinic receptor types are there?

A

5

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12
Q

Where are M1, M2 and M3 receptors found?

A

M1 - salivory glands, stomach, CNS

M2 - heart.

M3 - salivory glands, bronchial/visceral SM, sweat glands, eyes.

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13
Q

What type of receptor are Muscarinic receptors?

A

G protein - type 2 receptors.

7 transmembrane segments with a loop on the inside that activates the trimer G protein.

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14
Q

How do M1 and M3 receptors differ from M2 receptors.

A

M1 and M3 are linked to stimulatory G protein, Gq - increase IP3 and DAG production.

M2 - linked to inhibitory Gi prtoein - reduction in cAMP

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15
Q

What type of receptors are nicotinic receptors?

A

Ligand gated ion channels - type 1 receptors.

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16
Q

How many subunits do nicotinic receptors have?

A

5 - alpha, beta, gamma, delta, epsilon.

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17
Q

What is the significance of nicotinic receptor subunit combinations?

A

Subunit combination determines ligand binding properties.

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18
Q

What nicotinic receptors subunits exist at muscle and ganglionic type receptors?

A

Muscle - 2 alpha, beta, gamma, epsilon.

Ganglion - 2 alpha, 3 beta.

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19
Q

How do nicotinic receptor effects compare to that of muscarinic receptors?

A

Effect of Ach is relatively weaker in nicotinic.

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20
Q

What ion moves through nicotinic receptors to give an effect?

A

Na+

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21
Q

List potential target systems of mucarinic cholingeric receptors.

A

Eye, sweat glands, lung, heart, sweat glands, bladder, gut, vasculature.

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22
Q

What are the 3 main muscarinic effects on the eye?

A
  1. ciliary muscle contraction - accomodation for near vision (more convex lens)
  2. contraction of sphincter pupillae (iris circular muscle) - constricts pupil and improves intraocular drainage.
  3. lacrimation.
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23
Q

Label diagram of eye.

A
24
Q

Outline function of the sphincter pupillae.

A

open pathway for aqueous humour, allowing drainage via the canals of Schlemmand reducing intra-ocular pressure (since cornea and iris don’t receive blood supply)

25
Q

How can glaucoma occur?

A

Ruffling of the iris reduces angle of canal of Schlemm, inhibiting drainage of fluid.

26
Q

Outline muscarinic effects on the heart.

A

Receptors focused in atria, SA and AV nodes.

Reduced cAMP due to binding of M2 receptor –> reduced Ca2+ entry and increased K+ efflux –> reducded contractility and heart rate.

27
Q

Why can vasculature be targeted by ACh related drugs despite not receiving PNS innervation?

A

Ach acts on vascular endothelial cells to stimulate NO release via M3 receptor, inducing vasodilation –> reduced TPR.

(NO diffuses into VSMC from vascular endothelium)

28
Q

Give 4 muscarinic effects on exocrine glands.

A

salivation

increased bronchial secretions

increased gasto-intestinal secretions

increased sweating.

29
Q

Give an overview of muscarinic effects on the cardiovascular system.

A

Decreased heart rate

decreased CO

vasodilation

overall: sharp drop in blood pressure.

30
Q

How does non-vascular smooth muscle respond to muscarinic PNS innervation.

A

Excitatory responses.

Lung - bronchoconstriction.

Gut - increased peristalsis

Bladder - increased bladder emptying.

31
Q

Overview potential muscarinic effects on the body (7 things)

A
  • Decreased heart rate
  • Decreased blood pressure
  • Increased sweating
  • Difficulty breathing
  • Bladder contraction
  • Gastrointestinal pain
  • Increased salivation and tears
32
Q

Draw bethanechol and pilocarpine muscarinic receptor agonists.

A
33
Q

What kind of compounds are bethanechol and pilocarpine?

A

choline esters and alkaloids.

34
Q

Is pilocarpine a selective muscarinic agonist?

A

No (between types of muscarinic receptor)

35
Q

What is the half life of pilocarpine in the body?

A

3-4hr

36
Q

Is pilocarpine lipid soluble?

A

Yes

37
Q

What is the primary use of pilocarpine?

A

Local treatment for closed angle glaucoma.

38
Q

List some side effects of pilocarpine.

A

Blurred vision, sweating, gastro-intestinal disturbance and pain, hypotension, respiratory distress.

39
Q

Is bethanechol a selective muscarinic agonist?

A

Yes, for M3 receptors.

40
Q

Give some characteristics of bethanechol.

A

Resistant to degradation. Orally active. Limited access to brain. Half life - 3-4hr.

41
Q

What are the primary uses of bethanechol?

A

bladder emptying, gastric motility.

42
Q

Give some side effects of bethanechol.

A

sweating, impaired vision, bradycardia, hypotension, respiratory difficulty.

43
Q

What is the method of action of indirectly acting cholinomimetic drugs?

A

inhibit the action of acetylcholinesterase - increase effect of normal PNS stimulation.

44
Q

Give some examples of reversible and irreversible anticholinesterases.

A

Reversible - physostigmine, neostigmine, donepezil.

Irreversible - ecothiopate, dyflos, sarin

45
Q

What do cholinesterases do?

What two types are there?

A

metabolise acetylcholine to choline and acetate.

acetylcholinesterase (specific)

butyrylcholinesterase (pseudocholinesterase)

46
Q

Outline the distribution, selectivity and speed of acetylcholinesterase.

Outline its method of action (diagram)

A

Found in all cholinergic synapses.

Very rapid (> 10,000 reactions/second)

Highly selective for ACh

47
Q

What is the role of butyrylcholinesterase?

A

Maintain low plasma ACh and metabolise other esters (broad substrate specificity).

Not found in cholinergic synapses.

48
Q

What are the effects of cholinesterate inhibitors.

A

Low dose - enchanced muscarinic activity,

Moderate dose - further enhancement + increased transmission at all autonomic ganglia

High doe - toxic. Depolarising block at autonomic ganglia.

49
Q

How to reversible anticholinesterase drugs work?

A

Compete with ACh.

Donate Carbamyl group, blocking active site, preventing ACh binding.

Carbamyl group removed by slow hydrolysis.

50
Q

Give the half life and location of action of physostigmine.

A

Half life - 30 mins.

Primarily acts at postganglionic PNS synapse.

51
Q

What is physostigmine used for?

A

treatment of glaucoma and atropine poisoning.

52
Q

How do irreversible anticholinesterases work?

A

React with enzyme to leave large stable blocking group resistant to hydrolysis - new enenzymes must be made.

53
Q

What is ecothiopate used for?

A

Glaucoma. Prolonged duration of action.

54
Q

What are the side effects of ecothiopate?

A

sweating, blurred vision, GI pain, bradycardia, hypotension, resp. difficulty.

55
Q

What are the effecvts of anticholinesterases on the CNS?

A

Low doses - excitation, possible convulsions.

High doerses - unconsciousness, repiratory depression, death.

56
Q

How can organophosphate poisoning be treated?

A

Artificial respiration, atropine (IV), pralidoxime (IV).

Nb. phosphorylated enzyme ages within a few hours.

57
Q
A

LCRS - pharma (12 decks)

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