Influence of innocuous cervical vertebral movement on the efferent innervation of the adrenal gland in the rat

Short-term effects of manipulation to the upper thoracic spine of asymptomatic subjects on plasma concentrations of epinephrine and norepinephrine-a randomized and controlled observational study

OBJECTIVE

The purpose of this study was to investigate the short-term effects of spinal manipulation applied to a hypomobile segment of the upper thoracic spine (T1-T6), on plasma concentrations of norepinephrine (NE) and epinephrine (E) in asymptomatic subjects, under strictly controlled conditions.

METHODS

Fifty-six asymptomatic subjects were randomly assigned to receive either a chiropractic manipulative intervention or a sham intervention in the upper thoracic spine. A 20-gauge catheter fitted with a saline lock was used to sample blood before, immediately after, and 15 minutes after intervention. Plasma NE and E concentrations were determined using an enzyme-linked immunosorbent assay. Changes in plasma catecholamine concentrations were analyzed within and between groups using 1- and 2-sample t tests, respectively.

RESULTS

The plasma samples of 36 subjects (18 treatment, 18 control) were used in the analysis. Mean plasma concentrations of NE and E did not significantly differ between the 2 groups at any time point and did not change significantly after either the manipulative or sham intervention.

CONCLUSIONS

The results of this study indicate that a manipulative thrust directed to a hypomobile segment in the upper thoracic spine of asymptomatic subjects does not have a measurable effect on the plasma concentrations of NE or E. These results provide a baseline measure of the sympathetic response to spinal manipulation.

Measurement of the Vertebral Canal Dimensions of the Neck of the Rat with a Comparison to the Human

The aim of this study was to determine the dimensions of the vertebral canal in the neck of the rat, because little is known about the morphology of the rat's cervical spine. A comparison then was made to the vertebral canal in the neck of the human. In part 1 of this study, we determined the precision of three different methods to measure the vertebral canal. The error (coefficient of variation) in these methods was found to range from 1 to 8%. In part 2, we used a computer-based system to measure digital images of the vertebra and determined the anterior to posterior and the transverse vertebral canal dimensions in the neck of 19 young adult Sprague-Dawley rats. The anterior to posterior dimension of the vertebral canal was greatest at the upper cervical (C1-C2) level and progressively decreased in the more caudal segments (C3-T1). The transverse dimension was greatest at the atlas (C1) vertebra and smallest at the axis (C2) vertebra with a steady increase in the transverse dimension with more caudal segments and a maximum transverse dimension at the level of the C6 and C7 vertebra. This study has demonstrated that the vertebral canal in the neck of young adult rats is similar in some regards to that of human. However, there are clear differences between the rat and human. These may be associated with differences in the morphology of the spinal cord or postural differences such as the cervicothoracic lordosis in bipeds compared with that in quadrupeds.