AUTONOMIC PHARMACOLOGY

Question 1

What type of receptors are parasympathetic receptors?

Answer 1

Nicotininc muscarinic receptors

Question 2

What type of receptors are sympathetic receptors?

Answer 2

Noradrenaline receptors

Question 3

Which enzymes break down acetylcholine?

Answer 3

Esterase enzymes

Question 4

Which aspects of the nervous system do drugs target?

Answer 4

Junctions and synapses
Can target axons but its not specific

Question 5

What is hexamethonium?

Answer 5

• A drug that is no longer used.
• Blocks the voltage gated sodium and calcium ion channels
• Non competitive
• Selective antagonist for neuronal sub type of nicotinic receptor
• Blocks all effects of autonomic stimulation and blocks autonomic transmission as well as enteric
• Methonium derivative

Question 6

What type of receptors are found in sympathetic and parasympathetic ganglion?

Answer 6

Nicotinic receptors

Question 7

What are muscarinic agonists called?

Answer 7

Parasympathomimetic drugs because they mimic the effects of parasympathetic activation

Question 8

What are the effects of parasympathomimetics?

Answer 8

• Decreased heart rate
• Increased digestion
• smooth muscle contracts
• secretion of exocrine glands

Question 9

Effects of muscarinic poisoning?

Answer 9

Too much muscarine agonist which overstimulates the receptors
- Bradycardia
- vasoldilation
- pupil constriction

Question 10

What is the treatment for muscarine poisoning?

Answer 10

Atropine - an antagonist to muscarinic receptors and prevents too much muscarine from binding which can cause poisoning of the receptors

Question 11

What are alpha and beta adrenergic receptors?

Answer 11

They are receptors that are specific to catecholamines - adrenaline and noradrenaline

Alpha = mediate smooth muscle contraction and vasoconstriction

Beta = smooth muscle relaxation and vasodilation

Question 12

Describe muscarinic receptors

Answer 12

• They are transmembrane spanning and have 7 transmembrane segments
• Has 5 different subtypes

Question 13

Describe muscarinic receptors

Answer 13

• They are transmembrane spanning and have 7 transmembrane segments
• Has 5 different subtypes - M1-3 are important peripherally

Question 14

Where are M1, M2 and M3 receptors found?

Answer 14

• M1 = Stomach and salivary glands
• M2 = Cardiac
• M3 = Smooth muscle

Question 15

What are the 5 subtypes of adrenergic receptors and what do they do?

Answer 15

a1 = contract smooth muscle (vasoconstriction)
a2 = Central inhibition of sympathetic outflow, direct vasoconstriction
b1 = Increase heart rate and contractivity
b2 = relax smooth muscle - bronchodilation and vasodilation
b3 = relax smooth muscle and stimulate lipolysis

Question 16

Give two uses of a1 receptor agonists

Answer 16

• Vasoconstrictors with local anaesthetics (adrenaline and noradrenaline)
• Nasal decongestants (phenylephrinre)

Question 17

Give two uses of an a2 receptor agonist

Answer 17

• Hypertension treatment - acts on central a2
• Facial erythema in rosacea (Brimonidine which causes direct vasoconstriction)

Question 18

What are the two main uses of a1 receptor antagonists

Answer 18

• Hypertension
• Benign prostatic hyperplasia

Question 19

Which neurotransmitter binds to muscarinic receptors?

Answer 19

Acetylcholine

Question 20

Main use of b1 receptor agonists

Answer 20

Cardiogenic shock - adrenaline & dobutamine

Question 21

Main use of b2 receptor agonists (2)

Answer 21

• Asthma
• Delay of premature labour

Question 22

Main uses of beta receptor antagonists (5) and an example

Answer 22

Example: metoprolol
- Anginas, cardiac arrhythmias
- Hypertension
- Anxiety states
- Chronic heart failure
- Locally for glaucoma

Question 23

How can drugs affect/ alter sympathetic transmission?

Answer 23

Interfere with the processes involved in the synthesis of noradrenaline, the exocytosis of NA or the termination of noradrenaline signalling

Question 24

What is the main way in which noradrenaline signalling is terminated?

Answer 24

• Neuronal uptake by secondary active transporter NAT
• This terminates its action
• It is then repackaged into vesicles and if it isn’t needed it is broken down by the Monamine Oxidase enzyme (MAO)

Question 25

How do the secondary active NAT transporters work?

Answer 25

• They are co-transporters
• They co - transport catecholamines with Na+ or Cl-

Question 26

Which substances inhibit NAT?

Answer 26

• Cocaine
• tricyclic antidepressants (desipramine)

Question 27

What are the effects of cocaine?

Answer 27

• euphoria & excitement (CNS action);
• Can cause tachycardia & increased peripheral BP. The NAd that is released stays in the intracellular space for longer (as cocaine blocks NAT) and so activates receptors for longer amplifying its effects of sympathetic action
• It is also a local anaesthetic, Na+ ion channel inhibition

Question 28

What are MAO inhibitors?

Answer 28

• Used clinically as antidepressants
• Most irreversibly block MAOs
• You get increased levels of NA, dopamine & 5-HT (serotonin) in brain & peripheral tissues as MAO enzyme is blocked

Question 29

What are Indirectly-acting sympathetic amines?

Answer 29

• Amphetamine
• Structurally related to NA
• Transported into nerve terminal by NAT and into vesicles
• They move into the cell and displace NA which leaks out via NAT
• They have a similar effect on dopamine & 5-HT in CNS
• They have long-lasting effects that mimic those of NA – bronchodilation, vasoconstriction
• CNS effects underlie their use as substances of abuse