Rick, it seems norepinephrine helps regulate migroglia cells!

"In addition to DA neurons in the SNc postmortem patients with PD showed that norepinephrine (NE) neurons in the locus coeruleus (LC) also degenerate (not, vert, similar70% loss). The loss of NE neuron has been overlooked in PD."

Maybe the loss of NE leads to DEPRESSION and explains why newer antidepressants that affect both NE and serotonin (without side effects of the old drugs) are so effective in PD depression.

http://www.sciencedirect.com/science...53447fb82f1ff3