Nociceptive input from the rat thoracolumbar fascia to lumbar dorsal horn neurones

In anaesthetised rats, systematic electrophysiological recordings from dorsal horn neurones in spinal segments Th13-L5 were made to obtain information about the spinal nociceptive processing from the lumbar thoracolumbar fascia. Six to fourteen percent of the neurones in the spinal segments Th13-L2 had nociceptive input from the thoracolumbar fascia in naïve animals, no neurones responsive to input from the lumbar fascia were found in segments L3-L5. The segmental location of the receptive fields in the fascia was shifted 2-4 segments caudally relative to the spinal segment recorded from. Most neurones were convergent in that they received additional input from other deep somatic tissues in the low back (87%) and from the skin in the abdominal wall or the proximal leg (50%). The proportion of neurones responsive to input from the thoracolumbar fascia rose significantly from 4% to 15% (P < 0.05) in animals with an experimentally-induced inflammation of a low back muscle (multifidus). Moreover, neurones in spinal segment L3 - that did not receive input from the fascia in normal animals - responded to fascia input in animals with inflamed muscle. The data suggest that the nociceptive input from the thoracolumbar fascia contributes to the pain in low back pain patients.