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

Abstract

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.