Pharmacology Of ANS

Question 1

Cholinergic receptors types

Answer 1

• Nicotinic receptor

* Muscarinic receptor

Question 2

Nicotinic receptor type

Answer 2

Ligand-gated ion channel receptor (ionotropic)

Question 3

Muscarinic receptor type

Answer 3

G-protein coupled receptor (GPCR) (metabotropic)

Question 4

Nicotinic actions

Answer 4

• Skeletal muscle: promote Ms contraction
• Peripheral neuronal: stimulation of autonomic ganglia, secretion of cathecholamimes by adrenal medulla
• CNS neuronal (nAChR): regulate release of neurotransmitters, function on cognition and pain perception

Question 5

M1 receptor function

Answer 5

• Learning and memory

* GI secretion and motilty

Question 6

M2 receptor function

Answer 6

• SA node: decrease HR, AV node: decrease conduction

* Smooth muscle: increase contraction

Question 7

M3 receptor function

Answer 7

• smooth muscle: increased contraction (eg detrusor)

* Gastric and exocrine secretion

Question 8

Muscarinic receptors G protein types

Answer 8

• M1, M3, M5: Gq coupled

* M2, M4: Gi coupled

Question 9

Muscarinic actions on heart and blood vessels

Answer 9

• Heart: Bradycardia (negative chronotropy)
• Atria: Decreased contractile strength (negative intotropy)
• AV node: decrease in conduction velocity (negative dromotropy), increase in refractory period
• Blood vessels: dilatation via release of NO

Question 10

Muscarinic action on eye

Answer 10

• Contraction of sphincter muscle (miosis)
• Contraction of ciliary muscle (near vision)
• Decreased IOP (increased aqueous humour outflow via wider angle and open trabecular meshwork as a result of miosis)

Question 11

Muscarinic action on urinary bladder

Answer 11

• Contraction of detrusor

* Relaxation of trigone and sphincter

Question 12

ACh toxicology

Answer 12

AChE inhibitor drugs prevent destruction of ACh -> cholinergic over-activity

Question 13

ACh removal

Answer 13

Atropine large dose, maintained for > 72h

Question 14

Sympathomimetics

Answer 14

Adrenoreceptor agonists that mimic effect of sympathetic stimulation

Question 15

Sympatholytics

Answer 15

Adrenoreceptor antagonists that reduce/block sympathetic stimulation

Question 16

Termination of action of catecholamines

Answer 16

• Reuptake into nerve terminals
• Diffusion out of junctional cleft and reuptake at extraneuronal sites
• Metabolism by 2 enzymes: COMT, MAO

Question 17

2 main actions of sympathomimetic agents

Answer 17

• Alpha-adrenergic actions

* Beta-adrenergic actions

Question 18

Alpha-adrenergic actions

Answer 18

Stimulatory except on gut

Question 19

Beta-adrenergic actions

Answer 19

Inhibitory except on heart

Question 20

α₁ adrenergic receptor

Answer 20

GPCR - coupled to Gαq

Question 21

α₁ adrenergic receptor stimulatory effects

Answer 21

Contraction of VSM, sphincters and promote cardiac growth

Question 22

α₁-selective agonists

Answer 22

• Phenylephrine
• PPA (nasal decongestant)
• Midodrine

Question 23

α₁-selective antagonists

Answer 23

• Prazosin

* Doxazosin (hypertension, benign prostatic hypertrophy)

Question 24

α₂ adrenergic receptors type

Answer 24

GPCR - coupled to Gαi and Gαo

Question 25

α₂ adrenergic receptors function

Answer 25

Suppress sympathetic output and increase vagal tone

Question 26

α₂ adrenergic agonists

Answer 26

• Methyldopa, guanfacine: lower BP -> hypotension (treat hypertension)
• Apraclonidine, brimonidine: decrease prod of aqueous humour, reduces IOP (treat glaucoma)