Regeneration in the Nervous System

Question 1

What are the retrograde effects of a severed axon?

Answer 1

Interruption of normal supply of retrogradely transported signals (e.g., trophic factors) to the cell body
Arrival of new signals elicited at the injury site. 

After a cut is made to an axon, K+ leaks out of the cell and Ca++ comes in.
The retrograde flow of survival factors will cease.

Question 2

What are the anterograde effects of a severed axon?

Answer 2

The distal stump of cut axons undergoes Wallerian degeneration (degeneration of the proximal side post-injury)
Rapid (~1hr) fragmentation of distal stump after a latent phase (2-3 days)
Disintegration of myelin (1 week) 

Removal of axon remnants and myelin by macrophages and Schwann cells (~2-3 weeks) 


Question 3

What is GAP43?

Answer 3

A growth gene upregulated by Schwann cells

Question 4

CNS inhibitors of axon regeneration

Answer 4

NoGo A, myelin-associated glycoprotein (MAG)

Question 5

What is the function of chondroitin sulfate proteoglycan?

Answer 5

CSPGs have been implicated in inhibiting axonal regeneration and neurogenesis after central nervous system injury. Block with Chondroitenase.

Question 6

What are the receptors for myelin-derived inhibitors?

Answer 6

NogoR, p75NTR (neurotrophin receptor)

Question 7

Two CNS structures capable of neurogenesis

Answer 7

Hippocampus and olfactory bulb