Moreover, complete T4 transection significantly increases sprouting of C-fibers innervating the distal colon into the lumbosacral spinal cord (Hou et al., 2009), and over-expression of NGF using viral vectors injected into the lumbosacral dorsal horn increases the severity of AD in response to CRD (Cameron et al., 2006). This evidence concerns the gene NGF and Alzheimer disease.