Exercise Training Attenuates Proinflammatory Cytokines, Oxidative Stress and Modulates Neurotransmitters in the Rostral Ventrolateral Medulla of Salt-Induced Hypertensive Rats

It is known that the RVLM is a key area that controls blood pressure and sympathetic activity. This study focused on a few of the mechanisms that are taking place within RVLM during exercise and how they could affect adjacent pathways.

The authors suggest that pro-inflammatory cytokines such as TNF-alpha, IL-1b and IL-6 are involved in high blood pressure. To study the neural activity in the RVLM, the researchers focus on two mechanisms. GAD67 is an enzyme that regulates the production of GABA, which is known to inhibit the RVLM sympathetic activity. Fra-LI is a gene that, when expressed, demonstrates overexcitation. To assess these mechanisms, rats were fed high salt diets to induce high blood pressure.

One group of rats received a normal salt diet (NS), while another group was given a high salt diet (HS). For a period of twelve weeks, the rats were selected to receive exercise or sedentary conditions. Therefore, four different groups were formed: HS exercise, HS Sed, NS exercise, and NS Sed.

Beginning at week eight, blood pressure had significantly increased in the rats with high salt diets compared to the rats with normal salt diets. Within the group of rats fed a HS diet, the sedentary group continued to significantly increase whereas the exercise rats began to plateau. Following a similar pattern as blood pressure, higher RSNA was observed in the HS Sed rats than in the HS exercise rats. Although the HS exercise rats had lower RSNA, it was significantly higher than either the NS exercise or Sed rats. Pro-inflammatory cytokines were also detected in elevated levels in the RVLM and plasma of HS rats, but was shown to be less in exercise rats. The difference in PICs between HS Sed rats and HS exercise rats was very dramatic, yet the levels of TNF-alpha in NS Sed rats was less than half of the levels in HS exercise rats. 

In regards to the neural activity in the RVLM, the number of neurons containing GAD67 were much higher in NS exercise and Sed rats. HS exercise and Sed rats showed a higher level on neurons containing Fra-LI, which makes sense because it has the opposite effect of the inhibitory pathway of GAD67.

This study suggests that exercise can reduce neural activity of the RVLM and reduce blood pressure. What I found interesting about this study was the research into the imbalance between excitatory and inhibitory neurotransmitters. I'm interested in learning more about how this imbalance could possibly lead to many other pathways being affected which could bring about other damage.

Paul M