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MODA Drugs > Lecture Course 2: Peripheral Neural Transmission > Flashcards

Lecture Course 2: Peripheral Neural Transmission Flashcards

0
Q

* Botulinum toxin (general) *

A
  • Prevents neurotransmitter release
    • Preferential for cholinergic neurones
    1. Heavy chain C terminus -> ganglioside receptor
    2. N terminus translocates peptidase light chain into cell/vesicle
    3. Peptidase cleaves target snare
  • Symptoms
    • Somatic muscle weakness
    • Loss of autonomic cholinergic activity
      • (constipation, blurred vision, dry skin)
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1
Q

* Botulinum toxins B, D, F and G *

A
  • Prevent neurotransmitter release
    • Preferential for cholinergic neurones
    • Cleaves v-SNARE Synaptobrevin
  • Symptoms
    • Somatic muscle weakness
    • Loss of autonomic cholinergic activity
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2
Q

*Botulinum toxins A and E*

A
  • Prevent neurotransmitter release
    • Preferential for cholinergic neurones
    • Cleaves t-SNARE SNAP-25
  • Symptoms
    • Somatic muscle weakness
    • Loss of autonomic cholinergic activity
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3
Q

* Botulinum toxin C1 *

A
  • Prevent neurotransmitter release
    • Preferential for cholinergic neurones
    • Cleaves v-SNARE **Synaptobrevin **and t-snare SNAP-25
  • Symptoms
    • Somatic muscle weakness
    • Loss of autonomic cholinergic activity
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4
Q

* Tetanus toxin *

A
  • Blocks vesicle release in inhibitory interneurones
    • Retrogradedly transported to cell body, then transferred to inhibitory interneurone
    • Targets t-snare synaptobrevin whichprevents inhibitory neurotransmitter release
    • Motor neurones become more excitable
    • => tetanus
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5
Q

* Hemicholinium *

A
  • Blocks sodium-choline cotransporter, responsible for reuptake of choline into the cell to form Ach
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6
Q

Triethylcholine

A

Competitive substrate for Ach at transporters.

Released in place of Ach- a false transmitter.

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7
Q

Vesamicol

A

Non competitive reversible blocker of the vesicular ACh transporter.

This prevents vesicles from being filled with ACh.

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8
Q

* Beta Bungarotoxin *

A
  • Blocks ACh release.
    • Potassium channel binding region
    • Phospholipase A2 activity
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9
Q

* Alpha latrotoxin *

A
  • Binds to neurexins on plasma membrane and causes mass release of ACh by forming calcium permeable channels.
  • Can also inhibit potassium channels.
  • Black widow spider toxin
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10
Q

Alpha bungarotoxin

A
  • Irreversibly blocks n.m.j.
  • Does not block ganglions.
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11
Q

Trimetaphan

A
  • Competitive antagonist for ganglionic nAChR
  • Used for controlled lowering of blood pressure during surgery.
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12
Q

* Nicotine *

A
  • nAChR agonist
    • Selective for ganglionic nAChR
  • ​Phase I- depolarising block. Neuron cannot be stimulated further.
  • Phase II - desensitisation of nicotinic receptor - sodium channel inactivation. Neuron can be stimulated electrically directly but not via presynaptic neurone.
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13
Q

* Hexamethonium *

A
  • Non competitive ganglion blocker.
  • Use dependent blockade.
  • Causes loss of sympathetic and parasympathetic systems - ‘hexamethonium man’.
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14
Q

* D-tubocurarine *

A
  • Nicotinic receptor antagonist.
  • Non selective between ganglionic and nmj.
  • Leads to flaccid paralysis.
  • Cannot cross intestinal epithelium or placenta.
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15
Q

* Atracurium *

A
  • Competitive nAChR antagonist.
    • Also may block nicotinic autoreceptors => tetanic fade
  • Not orally active
  • Used in anaesthesia
    • Selective for white muscle
  • Short half life.
    • Ester - Broken down by plasma esterases.
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16
Q

* Pancuronium *

A
  • Competitive nAChR antagonist.
    • Also may block nicotinic autoreceptors => tetanic fade
    • Not orally active
  • Used in anaesthesia
    • Selective for white muscle
  • Long half life
    • Not broken down by plasma esterases.
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17
Q

Decamethonium

A
  • Depolarising nmj blockade.
    • Phase I - spastic paralysis.
      • Prolonged in multiply innervated muscles.
        • Deepened by anticholinesterases, reversible with non depolarising blockers
    • Phase II- flaccid paralysis.
    • Desensitisation block.
    • Reversed by anticholinesterases, deepened by curare like drugs.
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18
Q

Suxamethonium

A
  • Depolarising nmj blockade.
  • Used for short term muscle relaxation
    • eg. Intubation.
    • Can cause dangerous increases in plasma K+.
  • Phase I - spastic paralysis.
    • Prolonged in multiply innervated muscles.
    • Deepened by anticholinesterases, reversible with non depolarising blockers
  • Phase II- flaccid paralysis.
    • Desensitisation block.
    • Reversed by anticholinesterases, deepened by curare like drugs.
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19
Q

Acetylcholine

A
  • Non selective agonist for muscarinic and nicotinic receptors.
  • Broken down by AChE and BuChE
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20
Q

Carbachol

A
  • Non selective agonist for nicotinic and muscarinic receptors.
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21
Q

** * Muscarine ***

A

Muscarinic receptor agonist

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22
Q

Methacholine

A
  • Non selective muscarinic agonist.
  • Two isomers:
    • +-Methacholine is broken down by AChE and 200x more potent than - isomer
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23
Q

Cevimeline

A
  • Selective agonist for M3 muscarinic receptors (on glands and smooth muscle).
  • Used to treat dry mouth in Sjögren’s syndrome.

​

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24
Q

* Atropine *

A
  • Non selective antagonist for muscarinic receptors.
    • Used to dilate eye (opthalmic examination) - although too long lasting
    • Decrease bronchial and salivary secretions, bronchodilatation, increase heart rate, decrease GI motility
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25
Q

Pirenzepine

A
  • Selective antagonist for muscarinic M1 receptors (on the PNS and CNS).
  • Used to decrease gastric acid secretion.
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26
Q

* Darifenacin *

A
  • Selective antagonist for muscarinic M3 receptors (on glands and smooth muscle and oxytinic cells).
  • Used in cases of urinary incontinence.
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27
Q

M1 and M3 muscarinic receptors

A

Mechanism:

  • couple through Gq/11 - generation of IP3 and DAG through cleavage of PIP2
  • M1 only also inhibits potassium channels
  • M3 only also increases intracellular calcium concentration
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28
Q

M2 muscarinic receptors

A

Mechanism:

  • Couple to Gai
    • inhibits adenylyl cyclase.
    • cAMP decrease.
    • decreased VG calcium channel activation, lower heart excitability and less neurotransmitter release
    • beta gamma subunit opens potassium channel in SAN, decreasing heart rate
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29
Q

* Bethanechol *

A
  • Non selective agonist for muscarinic receptors.
  • Poorly absorbed from GI tract.
  • Used for systemic treatment for urinary retention.
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30
Q

* Pilocarpine *

A
  • Non selective agonist for muscarinic receptors.
  • Poorly absorbed across GI tract.
  • Used topically for glaucoma - absorbed through cornea and contracts cillary muscle.
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31
Q

* Edrophonium *

A
  • Short acting Anticholinesterase.
  • Reversible ionic interaction with AChE.
  • Used to diagnose myasthenia gravis.
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32
Q

* Neostigmine *

A
  • Medium length Anticholinesterase.
  • Forms weak covalent bonds with AChE.
    • Carbamylates active site
  • Reverses surgical block and used to treat myasthenia gravis.
33
Q

Sugammadex

A
  • Forms inactive complex in the plasma with non-depolarising n.m.j agents (eg. Atracurium)
  • Excreted in the urine.
34
Q

* Pralidoxime *

A
  • Reverses organophosphoric agent inhibition at n.m.j
  • Binds to phosphoric group and removes it
35
Q

Noradrenaline

A
  • Catecholamine.
  • Main sympathetic neurotransmitter, also involved in CNS.
  • Acts on:
  • a1 > a2 = B1 > B2
36
Q

Adrenaline

A
  • Catecholamine.
  • Synthesised in adrenal gland - hormone in periphery.
  • Acts on:
  • a2 > a1 > B
  • Used in treatment of extreme conditions eg. Anaphylatic shock, acute cardiac failure.
37
Q

Dopamine

A
  • Catecholamine.
  • Precursor for noradrenaline.
38
Q

Alpha-Methyltyrosine

A
  • Competitively Inhibits Tyrosine hydroxylase (TOH)
    • Catalyses Tyrosine -> DOPA
      • The rate limiting step for dopamine/noradrenaline/adrenaline production.
39
Q

* Carbidopa *

A
  • Inhibits DOPA decarboxylase
    • Catalyses the conversion of DOPA -> dopamine.
    • Only works peripherally
    • Administered alongside L-DOPA in treatment of parkinsons to reduce peripheral side effects
40
Q

Disulphiram

A
  • Inhibits dopamine Beta-hydroxylase (DBH)
    • catalyses dopamine -> noradrenaline.
    • Used in the treatment of alcohol abuse by a different mechanism.
41
Q

* Methyldopa *

A
  • False transmitter
    • acts on alpha 1 and alpha 2 adrenergic receptors
    • Less active than noradrenaline on alpha 1
    • More active on alpha 2
  • Used as an antihypertensive.
42
Q

* Reserpine *

A
  • Binds tightly to vesicular monoamine transporter.
  • This blocks uptake of NA and DA into vesicles.
  • Vesicular leakage of stored NA and DA into the cytoplasm causes long lasting depletion.
  • Use as an antihypertensive discontinued due to depression.
43
Q

* Tyramine *

A
  • Indirect sympathomimetic amine.
    • Displaces NA from vesicles.
    • Some displaced NA reaches synaptic cleft and activates adrenoreceptors.
  • Found in cheese, wine, marmite, soya beans.
  • May cause widespread vasoconstriction if too much ingested -‘cheese effect’.
  • In normal amounts converted to octopamine, a false transmitter.
  • Repeated use produces lower response due to less NA in vesicles - tachyphylaxis.
44
Q

Dexamfetamine

A
  • Indirectly acting sympathomimetic amine.
  • Evades monoamine oxidase and is taken up into vesicle.
  • Displaces noradrenaline, which may leave nerve and activate adrenoreceptors.
  • MDMA has similar effects, but also acts on 5HT2 receptors.
  • Repeated use produces lower response due to less NA in vesicles - tachyphylaxis.
45
Q

* Guanethidine *

A
  • Adrenergic neurone blocker.
  • Taken up into nerve by uptake 1 - compete with NA.
  • Block NA release in low repeated doses.
  • Unknown mechanism.
  • Act as indirect sympathomimetic amines in large doses.
46
Q

* Imapramine *

A
  • Tricyclic antidepressant which blocks NET (uptake 1).
  • Blocks catecholamine reuptake - sustains action
47
Q

* Cocaine *

A
  • Catecholamine uptake 1 blocker.
  • Blocks NET (presynaptic)
  • Sustains action of catelcholamines
48
Q

* Amitryptyline *

A
  • Catecholamine reuptake blocker.
  • Tricyclic antidepressant which blocks NET (uptake one on presynaptic terminal)
49
Q

* Clorgiline *

A
  • Monoamine oxidase (MAO) A inhibitor - blocks Catecholamine metabolism.
  • Used as antidepressant.
50
Q

* Selegiline *

A
  • Monoamine oxidase (MAO) B inhibitor - blocks Catecholamine metabolism.
  • Used in parkinsons treatment.
51
Q

* Tranylcypromine *

A
  • Non selective Irreversible inhibitor of monoamine oxidase (MAO).
  • Used in treatment of refractory (treatment resistant) depression.
52
Q

* Entacapone *

A
  • Catechol O-methyltransferase (COMT) inhibitor.
  • Blocks catecholamine metabolism, especially that associated with uptake 2.
  • Used in treatment of parkinsons disease.
53
Q

Mirabegron

A
  • Selective B3 adrenoreceptor agonist. -> Negative ionotropic effect.
  • Used in treatment of overactive bladder.
  • Relaxes bladder detrusor muscle.
54
Q

* Isoprenaline *

A
  • Beta-Adrenoreceptor agonist. P
  • reviously used in asthma to relax bronchial - but led to increase in heart rate.
55
Q

* Phenylephrine *

A
  • Alpha1 adrenoreceptor agonist.
  • Some action at B1
  • Used to raise blood pressure in acute hypotension
56
Q

MethylNA

A
  • Alpha adrenoreceptor agonist.
  • a2>>a1
57
Q

* Clonidine *

A
  • Alpha adrenoreceptor agonist.
  • a2>a1
  • Used as an antihypertensive.
58
Q

* Xylazine *

A
  • Selective a2 adrenoreceptor agonist.
  • Used as a sedative in veterinary medicine due to actions in CNS.
  • Advantage over other anaesthetics as no respiratory depression
59
Q

* Salbutamol *

A
  • Beta 2 adrenoreceptor agonist.
  • Some action at B1.
  • B2 selectivity allows use as a bronchial dilate in asthma without increasing heart rate
60
Q

* Dobutamine *

A
  • Beta adrenoreceptor agonist.
  • B1>> B2
  • Used in acute cardiogenic shock.
61
Q

* Phentolamine *

A
  • Alpha adrenoreceptor antagonist.
  • Obsolete antihypertensive due to reflex tachycardia.
  • Slight blocking action on toxic effects of noradrenaline in cardiac failure
62
Q

Phenoxybenzamine

A
  • Irreversible antagonist for alpha adrenoreceptors.
  • Similar to benzocholine mustard.
  • Used in combination with atenolol to prevent effects from catecholamine release during tumour removal surgery
63
Q

* Prazosin *

A
  • Alpha adrenoreceptor antagonist.
  • Selective for a1
  • Used as an antihypertensive
64
Q

Yohimbine

A
  • Alpha adrenoreceptor antagonist.
  • Strongly selective for a2
65
Q

* Idazoxan *

A
  • Alpha adrenoreceptor antagonist.
  • Strongly selective for a2
66
Q

* Propranolol *

A
  • Beta adrenoreceptor antagonist.
  • Ex antihypertensive agent - non selectivity gave rise to bronchiconstriction
  • Attenuation of toxic noradrenaline effects in heart failure.
  • Class II antidysrythmic. Sympathetic innervation can lead to dysrhythmia
67
Q

** Atenolol *

A
  • Beta adrenoreceptor antagonist.
  • Selective for B1
  • Used in combination with Irreversible inhibitor phenoxybenzamine to prevent effects from catecholamine release during tumour removal surgery
  • Used as an antihypertensive
  • Class II antidysrythmic. Sympathetic innervation can produce dysrhytmia
68
Q

* Butaxamine *

A
  • Beta-Adrenoreceptor antagonist.
  • Strongly selective for B2
69
Q

* Labetalol *

A
  • Adrenoreceptor antagonist.
  • Selective for a1, B1, B2
  • Four isomers with different actions.
  • Used as an antihypertensive during pregnancy.
70
Q

Tamsulosin

A
  • Selective a-1a adrenoreceptor antagonist.
  • Used in benign prostatic hyperplasia - relaxes smooth muscle of prostate and neck of bladder.
71
Q

Dutasteride

A
  • Used in conjunction with tamsulosin in treatment of benign prostatic hyperplasia.
  • Antiadrogenic effects - blocks testosterone synthesis.
72
Q

* Caffiene *

A
  • A1 receptor antagonist => wakefulness
  • Also non selectively inhibits phosphodiesterases.
73
Q

* Dipyridamole *

A
  • Blocks adenosine inactivation
  • Potent vasodilator PDE V inhibitor - raises cAMP
  • Used in treatment of congestive heart failure
74
Q

Glyceryl trinitrate

A
  • Nitric oxide donor.
  • Nitrovasodilator.
75
Q

Isosorbide dinitrate

A
  • Nitric oxide donor.
  • Nitrovasodilator.
  • Used in angina treatment.
76
Q

* Sildenafil *

A
  • Selective inhibitor of PDE 5 (selectively breaks down cGMP)
  • Used to treat impotence
  • Also in pulmonary arterial hypertension
77
Q

7-NI

A
  • NOS inhibitor.
  • Selective for NOS in neurones.
  • Does not effect eNOS or iNOS
78
Q

L-NMMA

A
  • Non selective inhibitor of NOS
  • D isomer not reactive
79
Q

L-NIO

A
  • Irreversible inhibitor of iNOS
  • Activated in macrophages
80
Q

* Asymmetric Dimethylargenine (ADMA) *

A
  • endogenous NOS inhibitor
  • Synthesised during post translational protein methylation
  • Increased in hypercholesterolaemia and renal failure

MODA Drugs (9 decks)

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