L7 Cough and Cold OTC

Question 1

What initiates the coughing reflex?

Answer 1

Stimulation of sensory nerves innervating the throat and lungs

• These sensory neurons contain several receptors that detect irritation (eg P2X3, TRPV1)
• Sensory neurons send this info to the cough centre in the brainstem medulla oblongata (region that controls breathing reflex)

Question 2

Efferent nerves via ________ and _______ nerves stimulate the __________, __________, and _______ to initiate a cough (“noisy expiration”)

Answer 2

Efferent nerves via parasympathetic and motor nerves stimulate the diaphragm, intercostal muscles and lungs to initiate a cough (“noisy expiration”)

Question 3

What are antitussives?

Answer 3

Cough suppressants

ie OTC drugs that inhibit the cough reflex

Question 4

Through which primary mechanism do antitussives inhibit the cough reflex?

Answer 4

By inhibiting the neurons in the medulla oblongata

Question 5

To what receptor is Codeine an agonist?

Where are they located and what type of receptor are they?

Answer 5

Codeine is a mu-opioid receptor agonist:

• mu-opioid receptors are located in the medulla oblongata as well as peripheral nerves innervating the respiratory tract
• Opioid receptors are inhibitory G-protein coupled receptors

Question 6

What happens upon activation of opioid receptors?

Answer 6

• Inhibition of calcium channels, activation of K+ channels and inhibition fo Adenylyl Cyclase (AC) (Gi)
• Neuronal inactivation and reduced transmitter release
• Agonist but causes NET inhibition

Question 7

What is a side effect of taking codeine to suppress cough?

Answer 7

The medulla oblongata is the respiratory centre as well as the cough centre - inhibition of medulla neurons will inhibit respiration

-Not recommended for those under 18

Question 8

What is dextromethorphan?

Answer 8

Antitussive:

• centrally active NMDA receptor atagonist
• inhibits neurons in the medulla oblongata (same as codeine but codeine is an agonist)
• Not very effective at treating cough

Question 9

What is the NMDA receptor?

Answer 9

Ligand-gated ion channel gated by glutamate (excitatory)

=rapid excitation of neurons

Question 10

What is Diphenhydramine?

Answer 10

• Antihistamine (H1 inverse agonist)
• H1 receptors are Gq coupled GPCRs located on respiratory smooth mm which stimulates sensory nerves producing cough
  
  • Diphenhydramine inhibits histamine action at these receptors
• Also crosses the BBB to suppress the medullary cough centre

Question 11

H1 receptors are ______ coupled GPCRs located on ________

Answer 11

H1 receptors are Gq coupled GPCRs located on Respiratory smooth mm