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Block 3 Up To Quiz 1 > Cholinergic Pharmacology Pt1 > Flashcards

Cholinergic Pharmacology Pt1 Flashcards

1
Q

Cholinergic neurotransmitter

A

Acetylcholine (primary NT from CNS to body)

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2
Q

Acetylcholine use as drug

A
  • rarely used as drug bc effects too generalized and diffuse and its too short acting
  • prototypic cholinergic agent for actions of cholinergic drugs
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3
Q

Cholinergic neurotransmission important for

A
  • important for normal fx CNS and PNS
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4
Q

in periphery cholinergic transmission occurs in both

A

autonomic and somatic nervous systems

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5
Q

Aceetycholine transmission ANS

A
  • in ganglia (including adrenal medulla) transmission= nicotinic cholinergic
  • in parasympathetic neuroeffector junctions (and some symp junctions) transmission = muscarinic choliinergic
  • heart smooth muscle, secretory glands
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6
Q

acetylcholine transmission somatic motor system

A

neuromuscular junction transmission is nicotinic cholinergic

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7
Q

muscarinic effects at neuroeffector junctions

A
  • generally reflect parasympathetic respones
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8
Q

dramatic vasodilation due to stimulation of

A

noninnervated or sympathetically innervated muscarinic receptors in blood vessels

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9
Q

muscarine effects heart

A

Must know:
-decrease rate and contraction force
Additional:

  • bradycardia bc depress pacemaker cells in SA node
  • prolongs refractory period and conduction time through AV node and atria, at high doses can cause AV block
  • negative inotropic effect decreasing force of contraction primarily in atria bc few muscarinic receptors in ventricles may -> slight decrease cardiac output
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10
Q

muscarinic effects GI tract

A

increase sections and peristalsis
decrease sphincter tone
overall effect- empty bowel

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11
Q

muscarinic effects urinary bladder

A
  • contract detrusor and relax sphicter

- facilitate uriation

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12
Q

muscarinic effects bronchioles

A
  • contract bronchiolar smooth muscle, decrease airways, increase secretions
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13
Q

muscarinic effects eye

A
  • contraction sphincter muscle of iris -> iris contraction
  • constrict ciliary muscle (acomidation near vision)
  • opens canals scheme -> drainage intraocular fluids and decreasing intraocular pressure
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14
Q

muscarinic effects exocrine glands

A
  • increase salivation (watery)
  • lacrimation
  • sweating (not horse)
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15
Q

bloodd vessels muscarinic effects

A
  • indirect relaxation via increase nitric oxide synthesis in endothelial cells
  • relax vascular smooth muscle and vasodilation decreasing peripheral vascular resistance -> decrease BP
  • effect on vascular smooth muscle reflects activation primarily of noninnervated muscarinic receptor on blood vessel endothelial cells
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16
Q

nicotinic receptors generally

A

excitatory low does inhibitory high dose

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17
Q

muscarine receptors generally

A

excitatory or inhibitory depends on tissue

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18
Q

sweating inenrvtion

A

sweating sympathetic innervation but mediated by muscarinic effect (Ach released onto receptors)

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19
Q

nicotinic effects autonomic ganglia

A
  • only evident at v high doses of ACh muscarinic effect on heart can be lethal unless muscarinic agonist present
  • response to stimulation of autonomic ganglia reflects sum parasympathetic and sympathetic effects and general sympathetic responses predominate
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20
Q

exceptions to sympathetic effects predominating response to stimulation of autonomic ganglia

A

GI and urinary tracts

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21
Q

General effect nicotinic effect autonomic ganglia

A
  • increase blood pressure
  • tachycardia
  • other sympathetic resposnes
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22
Q

in presence of atropine

A

only sympathetic effects seen

= atropine = muscarinic antagonist

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23
Q

nicotinic effects at neuromuscular junction

A
  • ACh causes contraction skeletal muscle
  • prolonged exposure and high doses -> tremors and fasciculations (twitches of muscle) terminating in depolarizing paralysis bc inactivation Na+ channels and desensitization nicotinic receptors
24
Q

sympathetic ganglia

A
  • synaptic terminals appear similar to those in CNS
  • presynaptic terminal have cluster round, clear vesicles near membrane thickening
  • cleft- 200 angstroms
  • post synaptic membrane- has thickened apperance
25
Q

parasympathetic ganglia

A
  • preganglionic fibers- large termination on post synaptic cells
  • terminal post ganglionic cholinergic innervation composed of long chains varicose fibers similar to adrenergic innervation
26
Q

calyx

A
  • single large termination of preganglionic fiber at parasympathetic ganglia on postsynaptic cell; covers almost half ganglion cells surface
27
Q

transmission parasympathetic ganglionic synapses occurs

A
  • chemically (via release acetylcholine)

- electrically (direct current spread calyx to ganglion cell)

28
Q

Varicosites

A

contain dense accumulation agranular vesicles assumed to release transmitter en passage

29
Q

post junctional membrane (parasympathetic) lack

A
  • obvious structural specialization seen in CNS, in ganglia, and in NMJ
30
Q

Steps Cholinergic Activation

A
  1. Choline taken up into prejunctional nerve
  2. Acetylcholine synthesized
  3. Acetyl choline transported into synaptic vesicles
  4. Acetyl choline released into junction
  5. Acetylcholine activates nicotinic cholinergic receptors and muscarinic cholinergic receptors -> cell response
  6. Degredation (actively occurs during receptor activation as well)
31
Q

What takes choline up into prejuncitonal nerve

A

high-affinity choline transporter (CHT1)

32
Q

Acetylcholine synthesis

A

sythesized from choline and acetyl CoA; catalyzed by choline acetyltransferease

33
Q

what transports acetylcholine into synaptic vesicles

A

H+-dependent vesiclar ACh transpoter (VAChT)

34
Q

acetylcholine released into junction how

A
  • quantal packets from vesicles

- some non-quantal release from cytoplasm

35
Q

Nicotinic cholinergic receptors response

A
  • in ganglia
  • direct response is electrical biding acetylcholine -> opening cation channel -> rapid depolarization post synaptic membrane -> initiation action potential
36
Q

Muscarinic cholinergic receptor

A
  • in NEJ
  • activation of receptor by acetylcholine -> activation of receptor by acetylcholine -> activation selective G-proteins -> transduce signal to various effector proteins
37
Q

degradation acetylcholine

A

primarily by acetycholinesterase

- choline generated by hydrolysis transported into prejunectional nerve cell by CHT1 and recycled

38
Q

Nicotinic receptors what type of receptor

A

ligand gated ion channel

39
Q

activation nicotinic receptors description

A
  1. 2 acetylcholine bind
  2. Nonselective cat-ion channels open
  3. Depolarization postsynaptic or post junctional cell
40
Q

Nicotinic receipts location and subtypes

A

Location: ganglionic synapses and neuromuscular junctions
Subtypes: two major families muscle (NMJ form) and neuronal receptors

41
Q

structure nicotinic receptor

A
  • 4 transmembrane domain

- M2 subunits face interior making pore for ion channel

42
Q

where does Ach bind nicotinic receptor

A

binds to side Alpha subunit usually at y or s interface -> conformational change opening pore allowing through monovalent ions

43
Q

Muscarinic acetylcholine receptors what type receptor

A
  • GPCR (therefore 7 membrane spanning domain)
44
Q

Muscarinic acetylcholine receptor activation steps

A
  1. Acetylcholine binds to receptor
  2. Coupling to and activation of G proteins induced ->
    - inhibition adnenylyl cyclase
    - activation phospholipase C-> DAG and IP3 formation and/or changes ion channel activity
45
Q

Muscarinic acetylcholine receptors found where

A
  • parasympathetic effector junctions

- a few sympathetic NEJ

46
Q

subtypes muscarinic receptors

A
  • M1-M5
  • M1,M3,M5: couple to Gq -> activate phospholipase
  • M2,M4 couple to Gi -> inhibit adenyl cyclase and stimulate K+ channels and inhibit voltage gated Ca2+ channels
47
Q

pathways -> muscarinic smooth muscle contraction

A

Pathway 1:
1. Acetylcholine -> M3 receptor -> Gq -> activate PLC (phospholipase C) ->cleaves PIP2 -> DAG and IP3 -> IP3 stimulates Ca2+ release -> contraction smooth muscle
Pathway 2:
Acetylcholine -> M2 receptor -> Gi -> inhibition adenylyl cyclase (AC) -> reduce levels fo cAMP -> decrease relaxation (ie contraction)

48
Q

sympathetic system and parasympathetic system adenycyclase

A

sympathetic system stimulates adenycyclase increasing levels cAMP increasing smooth muscle relaxation?

parasympathetic system decreases relaxation and decreases sympathetic effect by inhibiting adenylyl cyclase via Gi via M2 receptor

49
Q

Characteristics of nicotinic muscle cholinergic receptors

A
  • 2 alpha subunits
  • 1 beta subunit
  • 1 y subunit
  • 1s subunit
50
Q

Characteristics of neuronal cholinergic receptors

A
  • 2 alpha subunits

- 3 beta subunits

51
Q

M2

A

primary receptor type in heart mediating contraction reduction (on smooth muscle, stimulates contraction)

52
Q

M3

A
  • secretory glands, increase secretions

- on smooth muscle stimulates contraction

53
Q

CNS contains which subtypes muscarinic receptors

A

CNS contains all subtypes muscarinic receptors

54
Q

what causes relaxation sphincters in urinary and GI tracts

A
  • release dilatory peptides from intrinsic ganglia or parasympathetic nerves
55
Q

blood vessels relax how

A

consequence of release of nitric oxide form endothelium

Block 3 Up To Quiz 1 (24 decks)

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