Neuromodulation reduces c-fos gene expression in spinalized rats: a double-blind randomized study

Area of Science:

• Neuroscience
• Urology
• Physiology

Background:

• Sacral neuromodulation is a recognized treatment for various voiding dysfunctions.
• The precise mechanism underlying sacral neuromodulation remains incompletely understood.
• Investigating the role of afferent c-fiber activity is crucial for elucidating treatment mechanisms.

Purpose of the Study:

• To determine if the inhibition of afferent c-fiber activity is the primary mechanism behind sacral nerve root neuromodulation.
• To evaluate the impact of sacral neuromodulation on bladder hyperreflexia and neuronal activity in a rat model.

Main Methods:

• Female Sprague-Dawley rats underwent spinal cord transection at T9 to induce bladder hyperreflexia.
• Electrical stimulation of sacral nerve roots (S1) was applied for three weeks.
• Immunocytochemistry was used to quantify c-fos protein expression, a marker of neuronal activity, in the L6 spinal cord segment.

Main Results:

• Neuromodulation significantly reduced peak bladder pressure in hyperreflexic rats (from 82.4 cm H2O to 30.4 cm H2O).
• A significant decrease in c-fos positive neurons was observed in the neuromodulation group compared to the acetic acid sham group (93.2 vs. 160.6 cells/section).
• No significant difference in c-fos expression was found between the saline sham and neuromodulation groups.

Conclusions:

• Sacral dorsal root neuromodulation effectively reduces bladder hyperreflexia in spinalized rats.
• The observed reduction in c-fos gene expression suggests that neuromodulation inhibits afferent c-fiber activity.
• These findings support the hypothesis that afferent c-fiber inhibition is a key mechanism in sacral neuromodulation for voiding dysfunction.