Neuroscience Week 3: Opioid actions

Question 1

µ opioid receptors expressed where?

Answer 1

CNS and body

but particlarly care about brain, brainstem (PAG, Medulla) Spinal cord

Question 2

Lamina II and opioids

Answer 2

Interneurons for pain modulation. Act locally.

inhibit pain because when opioids bind to lamina II they bind and inhibit excitatory neurons but also activate inhibiting neurons that inhibit lamina I neurons and Lamina V neurons

this is important because Lamina I and V have 2nd order neurons that relay pain, so in inhibiting these pain is inhibited

Question 3

Descending modulation of pain

Answer 3

Periaqueductal gray projects to brainstem sites neurons in the Ventral Medial Medulla (Raphe Nuclei)

Ventral medial Medulla axons descend to the spinal cord and inhibit pain in 3 ways

1. Disinhibits inhibitory interneurons only in lamina II so basically disinhibition of inhibitory neurons (excites Lamina II neurons)

2. Directly inhibit postsynaptic 2nd order lamina I and V neurons

3. Directly inhibit presynaptic Aδ & C nociceptor terminals

What you are really trying to do is excite Lamina II inhibitory neurons

Question 4

Opioid Pharmacology Overview

Answer 4

Question 5

M3G toxicity Seizures

Answer 5

think it has to do with via GABA/glycinergic system

Question 6

M6G toxicity

Answer 6

enhanced opioid actions and can cause respiratory depression