NGF are powerful proteins (medicines) secreted by Schwann cells (glia) and designed to rescue neurons from death.(Fields, R. Douglas, PhD. The Other Brain. p 88-90. NY: Simon & Schuster, 2009.)

Glial cells are constantly secreting substances (e.g., peptides) that can nourish neurons or that can weaken/destroy them. (Pert, Candace, PhD. Your Body is Your Subconscious Mind. Audio Cassettes. CO: Sounds True, 2000.)