Dysfunction of the cervical vertebral column may produce headaches and cause disturbances to balance and posture. It is also known that there is a high density of sensory receptors in the paravertebral musculature in the neck. However, little is known about how afferent nerves from the vertebral column and its associated ligaments influence the central nervous system. In order to study their central effects, it is important to first identify the locations in the central nervous system that are likely to receive input from these nerves. Therefore, the aim of this study is to determine the regions of the spinal cord and brain that receive terminals from the nerves innervating the cervical vertebral column.

The study will be divided into a series of four experiments designed to label, transganglionically, terminals of afferents innervating the cervical intervertebral discs, juxtaposed ligaments and the intra- and para-articular tissue of the cervical zygapophyseal joints of rats. Each of three neuroanatomical labelling compounds (horseradish peroxidase, wheat germ agglutinin conjugated horseradish peroxidase and cholera toxin subunit B conjugated horseradish peroxidase) will be used in each series of experiments. In the first series of experiments, nerve branches innervating a single cervical zygapophyseal joint (in any one rat) will be exposed to the labelling compounds. In the second series of experiments a micro syringe will be used to inject the tracer substances into the joint cavity and the third series of experiments will involve exposing the para­ vertebral tissue surrounding the zygapophyseal joints to the tracing compounds. In the fourth series, branches of the sinuvertebral nerve and vertebral nerves innervating the intervertebral discs and associated ligaments will be exposed to the tracing compounds. Following a post-labelling survival period of 3-72 hours, the rats in each series will be sacrificed by anesthetic overdose and perfused with fixative. The spinal cord, brainstem and sympathetic ganglia of the neck will be removed at post-mortem and treated with chemicals so that the tracer compounds in the central terminals of the nerves from the cervical vertebral column can be visualised and their locations plotted.

The locations of the central terminals will provide indirect evidence about the location of neurons likely to receive direct input from the nerves innervating the cervical vertebral column. In future experiments, these neurons will be studied to determine how they respond to natural stimulation of the head and neck.

They will also be studied in circumstances in which the biomechanical integrity of cervical vertebral motion units has been compromised as, for example, might occur when a vertebral subluxation exists.

Grant Value: $33,002
Chief Investigator: Dr Philip Bolton – University of Newcastle
Status: Complete

Outcomes: 

  • October 1995
    This is an on-going study which involved the labelling of nerves that innervate the joints in the neck of rats and then identifying what parts of the rats brain and spinal cord received direct input from these nerves. This study has shown that the small knuckle like (zygapophysial) joints in the neck and the muscles that cross and/or attached to these joints have nerves that send information to parts of the spinal cord which are known to be involved in the relay of information about painful stimuli. Of particular interest was the finding that nerves from these joints also terminate in regions of the spinal cord which are involved in the control of posture and balance. This finding provides evidence that information from these joints may also directly influence our posture and balance.  However, this study does not tell us anything about what effect the nerves from these joints have on the central nervous system and how they influence posture and balance. These are questions currently under investigation.