Electroacupuncture decreases c-fos expression in the spinal cord induced by noxious stimulation of the rat bladder

Purpose: The present study investigated the effects of noxious stimulation of the lower urinary tract on neuronal fos protein expression in the spinal micturition center of rats and also examined the effects of electroacupuncture (EA) on fos expression induced by noxious stimulation of the lower urinary tract. Materials and. Methods: Experiments were conducted on 21 female Sprague-Dawley rats divided into four groups. Group 1 rats (n = 5) served as normal controls. Group 2 rats (n 5) received EA at the Sanyinjiao acupoint. Group 3 animals (n = 6) were catheterized through the urethra and instilled with 1% acetic acid, and group 4 (n = 5) animals received EA 1 hour before 1% acetic acid instillation. All animals underwent arterial perfusion, laminectomy, and spinal cord removal. Spinal cords were sectioned and processed for immunohistochemical staining for fos protein. Results: No fos protein was detected in any spinal neurons in normal control animals, and either none or few (0 to 4 cells/section) fos-immunoreactive (fos-IR) cells were seen in animals treated with EA. Noxious stimulation of the lower urinary tract with 1% acetic acid drastically increased the number of fos-IR neurons (39 to 127 cells/L-6 section, mean 76.17 +/- 13.98; 28 to 77, cells/S-1 section, mean 59 +/- 8.30; 7 to 35 cells/S-2 section, mean 19.83 +/- 4.10). However, EA administered I hour before 1% acetic acid instillation significantly decreased the number of fos-IR neurons resulting from chemical irritation (0 to 50 cells/L-6 section, mean 19.8 +/- 9.33; 0 to 47 cells/S-1 section, mean 13.2 +/- 9.12; 0 to 37 cells/S-2 section, mean 13.6 +/- 7.31). Conclusions: Our study demonstrates that bladder instillation with 1% acetic acid induces fos protein expression in the spinal micturition center of the rat and that electroacupuncture can reduce this expression. These results suggest a link between electroacupuncture and reduction in spinal neuronal cell activity.