The periaqueductal gray matter (PAG) and the nucleus raphe magnus and adjacent
structures of the rostral ventromedial medulla (RVM), with their projections to the spinal
dorsal horn, constitute the “efferent channel” of a pain-control system that “descends” from
the brain onto the spinal cord. Considerable evidence has recently emerged regarding
participation of this system in persistent pain conditions such as inflammation and
neuropathy. Herein, this evidence is reviewed and organized to support the idea that …