Experimental Disc Herniation in the Rat Causes Downregulation of Serotonin Receptor 2c in a TNF-dependent Manner

Background

During recent decades, the knowledge of the pathophysiology of disc herniation and sciatica has drastically improved. What previously was considered a strict biomechanical process is now considered a more complex interaction between leaked nucleus pulposus and the tissue in the spinal canal. An inflammatory reaction, with tumor necrosis factor (TNF) playing an essential role, has been demonstrated. However, the exact mechanisms of the pathophysiology of disc herniation remain unknown.

Questions/purposes

In this study we use an animal model to investigate (1) if and/or how experimental disc herniation affects gene expression in the early phase (24 hours postsurgery) in the dorsal root ganglion; and (2) if TNF inhibition can reduce any observed changes.

Methods

A rat model of disc herniation was used. Twenty rats were evenly divided into four groups: naïve, sham, disc herniation, and disc herniation with TNF inhibition. The dorsal root ganglion of the affected nerve root was harvested 24 hours after surgery and analyzed with a TaqMan Low Density Array^® quantitative polymerase chain reaction assay. Gene expression levels in sham were compared with disc herniation to assess question 1 and disc herniation to disc herniation with TNF inhibition to assess question 2.

Results

Experimental disc herniation caused a decrease in the expression of the serotonin receptor 2c gene (p = 0.022). TNF inhibition was found to reduce the observed decrease in expression of serotonin receptor 2c (p = 0.037).

Conclusions

Our results suggest that a decrease in the expression of the serotonin receptor 2c gene may contribute to the pathophysiology of disc herniation. Further research on its involvement is warranted.

Clinical Relevance

This pilot study gives a brief insight into cellular changes that may contribute to the pathophysiology of disc herniation. This knowledge may contribute to the development of more and better treatment options for patients with disc herniation and sciatica.     

Is there a trend of decreasing prevalence of TMD-related symptoms with ageing among the elderly?

Objective. Older adults have not been studied as much as younger ones regarding prevalence of TMD-related symptoms. The aim was to assess the prevalence of TMD-related symptoms in two population samples, 70 and 80 years old. Materials and methods. Identical questionnaires were in 2012 sent to all subjects born in 1932 and 1942 living in two Swedish counties. The response rate was 70.1%, resulting in samples of 5697 70- and 2922 80-year-old subjects. The questionnaire comprised 53 questions. Answers to questions on problems regarding TMD-related symptoms and awareness of bruxism were analysed. Results. Twelve per cent of the women and 7% of the men in the 70-year-old group reported some, rather great or severe problems regarding TMD pain. In the 80-year-olds the prevalence was 8% and 7%, respectively. Subjects who had problems with TMJ sounds reported difficulty to open the jaw wide 6-times and TMJ pain 10–13-times more frequently than subjects without such problems. Changes of taste and awareness of bruxism were the only variables significantly associated with TMD symptoms in both age groups. Number of teeth was not significantly associated with any of the TMD-related symptoms. Conclusions. Most of the elderly subjects had no severe problems with TMD-related symptoms, but 12% of the 70-year-old women reported some, rather great or severe problems. The marked gender difference at age 70 had disappeared in the 80-year-old group. The prevalence was lower among the 80- compared with the 70-year-old subjects of both sexes. The results support the comorbidity between TMD-related symptoms and general health problems.