44 Neurophysiology tutorial 1 Mechanism-based treatment of pain

Question 1

What is the main mechanism of lidocaine in treating pain (with relation to TRPV1)?

Answer 1

Na+ channel blocker responsible for depolarization - block AP generation , thus block neural signal transmission by TRPV1 to the dorsal root ganglion (SG) to suppress pain perception

Question 2

State properties of TRPV1 channels that render it as a suitable transducer of noxious signals.

Answer 2

1. Non-selective channel, Na+ and Ca2+ can all pass

2. Polymodal nociceptor, detecting a wide range of stimuli

Question 3

Effect of capsaicin on TRPV1 channels?

Answer 3

Open channels and introduce cations into cell to increase RMP

Question 4

__________ receptors are involved in chronic pain.

Answer 4

NMDA receptors.

> induce LTP causing chronic pain.

Question 5

State how NMDA receptors are involved in mechanism of sensitization of dorsal horn in injury.

Answer 5

High glutamate release > opening of NMDA receptor > Ca2+ influx > induce AMPA receptors > many Na+ get into cell to produce LTP.

(increase in Ca2+ cause release in NO back to synapse, stimulate more glutamate release and NMDA and AMPA receptor expression)

Question 6

What is neural plasticity?

Answer 6

refers to the ability of neurons to change in form and function in response to alterations in their environment.
(memory, learning, chronic pain)

Question 7

Give example of NMDA receptor antagonists and side effect.

Answer 7

Ketamine;

abuse use will cause memory loss as NMDA receptors may affecting learning and memory