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Pharm > Cholenergic receptors > Flashcards

Cholenergic receptors Flashcards

1
Q

what kind of receptor/neurotransmitter do preganglionic parasympathetic neurons synapse with?

A

Acetylcholine on nicotinic receptors.

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2
Q

what kind of receptor/neurotransmitter do postganglionic parasympathetic neurons synapse with?

A

Acetylcholine on muscarinic receptors

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3
Q

what kind of receptor/neurotransmitter do preganglionic sympathetic neurons synapse with?

A

Acetylcholine on nicotinic receptors

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4
Q

what kind of receptor/neurotransmitter do postganglionic sympathetic neurons synapse with?

A

Norepi at adrenergic receptors

Except sweat glands which are innervated by cholinergic sympathetic fibers

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5
Q

Nicotinic acetylcholine receptor type

A

Ligand gated Ion channel (Na+, K+, Ca2+)

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6
Q

Nicotinic agonists

A
  • Acetylcholine

- Nicotine

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7
Q

Nicotinic antagonists

A
  • Muscle relaxants
    • Nondepolarizing blockers
    • Depolarizing blockers
  • Ganglionic blockers
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8
Q

Acetylcholine properties

A
  • Endogenous neurtotransmitter
  • Quaternary ammonium
  • Activates nicotinic and muscarinic receptors
  • Rapidly hydrolyzed by acetylcholinesterase
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9
Q

Nicotine properties

A
  • Selective for nicotinic receptors
  • tertiary ammonium; enters CNS
  • Drug of abuse
  • Highly toxic at large doses
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10
Q

Nondepolarizing blocker properties

A
  • Competitive antagonist of muscle nicotinic receptors

- indirectly antagonized by acetylcholinesterase inhibitors, which increase levels of endogenous acetylcholine

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11
Q

Depolarizing blockers mode of action

A
  • Nicotinic agonists
  • Initial muscle fasciulations(Disorganized contractions) due to direct stimulation of muscle receptors progress to
  • Phase I block(depolarizing): flaccid paralysis block is voltage gated Na channel inactivation . Phase I block is enhanced by acetylcholinesterase inhibitors
  • Phase II block(desensitizing): membrane repolarizes but paralysis continues.
  • succinylcholine is resistant to acetylcholinesterase, but is rapidly hydrolyzed by plasma cholinesterase.
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12
Q

Ganglionic blockers mode of action

A

effects depend upon predominant tone, so tend to increase heart rate(by antagonizing parasympathetic tone) and decrease blood pressure(by antagonizing sympathetic tine)
-Originally used for treatment of hypertension, but replaced by more specific agents

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13
Q

Muscarinic acetylcholine receptor types and subtype

A 
G-protein coupled receptor
5 subtypes(m1-m5)
3 subtypes defined pharmacologically
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14
Q

M1 subtype effects and 2nd messengers

A

Neural subtype
-Nerve terminals:
decrease transmitter release
-Increase PLC activity, DAG ,& IP3

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15
Q

M2 subtype effects and 2nd messengers

A

Cardiac subtype

  • Decrease heart rate and contractility
  • Decrease cAMP
  • K+ channel activation
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16
Q

M3 subtype effects and 2nd messengers

A

Glandular

  • Eye: contracts circular and ciliary muscles
  • Vascular endothelium release NO
  • Bronchial Smooth muscle contraction
  • GI tract: increase contraction, relaxes sphincters, Increase secretion
  • bladder wall contraction, sphincter relaxation
  • uterus contraction
  • Penis erection
  • Increase PLC activity, DAG , IP3, & cyclic GMP
17
Q

Direct acting agonist and selectivity

A
  • Acetylcholine, carbamylcholine (nonselective)

- Muscarine, pilocarpine (muscarinic-selective)

18
Q

Therapeutic uses

A
  • Promote bladder emptying
  • Stimulation of GI activity in GI disorders
  • contraction of pupil for surgery
  • reduce intraocular pressure in open angle glaucoma contracting ciliary body facilitating drainage.
19
Q

Muscarinic toxicity effect

A 
"SLUDGE"
-Salivation
-Lacrimation
-Urination
-Diarrhea
-GI upset
-Emesis
Bronchoconstriction
20
Q

Muscarinic antagonists

A
  • Belladonna alkaloids
    • Atropine(Less CNS effect)
    • Scopolamine(CNS depression)
  • Tricyclic antidepressants (secondary to antidepressant action)
21
Q

Therapeutic effects of muscarinic antagonists

A
  • Management of peptic ulcers
  • reducing excessive salivation
  • antitremor (Parkinson’s and side effects of antipsychotic drugs)
  • Prevention of motion sickness
  • ophthalmology(mydriasis and cycloplegia)
  • relief of acute rhinitis
  • treatment of bradycardia from excessive vagal tone
  • Bronchodilation
  • relaxation of GI smooth muscle for endoscopy
  • antidote for poisoning with cholinergic agonists or esterase inhibitor
22
Q

Acetylcholinesterase inhibitors mode of action

A

Block action of acetylcholinesterase by occupying the active site and increasing duration of action of acetylcholine in both muscarinic and nicotinic.

23
Q

3 types of acetylcholinesterase inhibitors and duration of action

A
  • Alcohols: competitive inhibitors’ rapidly reversible(2-10 min)
  • Cabamate esters: slowly reversible (0.5-6hrs) covalent bond. (most commonly used clinically
  • Organophosphates: slowly reversible covalent phosphate bond which progresses to an irreversible bond.
24
Q

clinical use of Acetylcholinesterase inhibitors

A

-Myasthenia gravis
-termination of effect ts of muscle relaxants
-treatment of hyperthermia or supraventricular tachycardia due to antimuscarnic intoxication
-treatment of glaucoma(topically)
-Treatment of post surgical paralytic ileus
-treatment of urinary bladder stony
treatment of Alzheimer’s disease

25
Q

Toxicity of Acetylcholinesterase inhibitors and treatemnt

A
  • SLUDGE
  • Neuromuscular blockade including respiratory paralysis
  • Treatment: Atropine for muscarinic symptoms, Pralidoxime to regenerate esterase. Respiratory support

Pharm (10 decks)

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