Spencer Brown

Question 1

In a depolarized state, DRG sensory neurons that had previously received a peripheral axotomy do not grow neurites.

Answer 1

F

Question 2

After a peripheral axotomy, L-type calcium channel expression is up-regulated within DRG sensory neurons.

Answer 2

F

Question 3

Enes proposes that electrical activity within DRG sensory neurons:

Answer 3

inactivates the genetic growth program within these neurons; is a sensor for when the embryonic neuron has innervated its target

Question 4

“Knockout” mice displayed greater regeneration after nerve crush compared to normal mice. What gene was “knocked out” in these mice?

Answer 4

L-type Ca2+ channel

Question 5

Explain in detail the mechanism by which the growth program of a DRG sensory neuron is kept in a “off” state by its peripheral target.

Answer 5

When connected to its peripheral target, the sensory neuron is producing electrical activity that is evoked from sensory stimuli. Depolarization of the sensory neuron leads to the activation of voltage-gated calcium channels and therefore an influx of calcium ions into the neuron. Presumably, this calcium current affects gene transcription and either leads to the production of growth inhibitory factors or transcription factors that suppress growth promoting genes.