Nerve supply to the posterior longitudinal ligament and the intervertebral disc of the rat vertebral column as studied by acetylcholinesterase histochemistry. I. Distribution in the lumbar region.

The nerve supply to the posterior longitudinal ligament (PLL) and the intervertebral disc (IVD) of the lumbar vertebra was investigated by acetylcholinesterase (AchE) enzyme histochemistry in the rat. The meningeal branch of the spinal nerve (the sinuvertebral nerve) enters the vertebral canal and divides into ascending and descending branches which fuse with those from adjacent vertebrae. They give off transverse branches, connecting with those from the opposite side to form the superficial nerve fibre network in the intervertebral segment, which spreads to the vertebral segment of the PLL. Apart from this superficial nervous network, many nerve fibres enter through the posterolateral portion of the annulus fibrosus (AF) and form a dense, fine nerve fibre network in the deep layer of the intervertebral portion of the PLL and the superficial layer of the AF. Nerve fibres and terminals cannot be found in the deep layer of the AF or the nucleus pulposus. In the central part of the deeper nerve network there are few nerve terminals whereas there are abundant free nerve endings in the peripheral zones. It is suggested that these abundant nerve fibres may be correlated with various functions characteristic of this region and that they may be important in the regulation of movement and posture in the vertebral column.