Change of Bladder Afferent Neuron after Intravesical Electrical Stimulation

Hong, Chang Hee; Kim, Young Sik; Kim, Jang Hwan; Noh, Ji Yeun; Ko, Hae Kyung; Kim, Chan Soo; Han, Sang Won

Abstract

PURPOSE: There have been reports on the clinical benefits of intravesical electrical stimulation (IVES) in patients with an increased residual urine or reduced bladder capacity. However, studies on the underlying mechanism of IVES have been limited to the A delta afferent and parasympathetic neurons. This study sort to investigate the changes in the expression of the C-fos protein in the thoracolumbar and lumbosacral spinal cord in order to determine the effect of IVES on the C fiber afferent nerve.
MATERIALS AND METHODS
Twenty Sprague-Dawley rats were divided into four groups; group 1 (n=5) served as a sham operation, groups 2 (n=5) were instilled with normal saline, groups 3 (n=5) were instilled with 1% acetic acid, and group 4 (n=5) received IVES prior to the administration of 1% acetic acid. The spinal cord was removed at the thoracolumbar (T13-L2) and lumbosacral (L5-S1) levels. Changes in the levels of the C-fos protein in the spinal cord were measured by western-blot analysis.
RESULTS
The relative density of the C-fos expression, 2 hours after IVES, was significantly higher, and the fos protein expression induced by IVES was decreased to the sham levels by the 5th day following the IVES. Therefore, it was decided that a 5 day interval between the IVES and the noxious stimulation with acetic acid should be used to avoid the superimposition of C-fos expression. The relative density of the C-fos protein, following noxious stimulation with 1% acetic acid, was significantly higher compared to the saline distension in both the T13-L2 and L5-S1 levels of the spinal cord. However, the IVES prior to the administration of 1% acetic acid significantly decreased the relative density of the C-fos protein at both the T13-L2 and L5-S1 levels of the spinal cord compared to the rats with noxious stimulation alone.
CONCLUSIONS
IVES reduces the expression of C-fos, which is mainly conveyed by the unmyelinated C fibers in the noxiously stimulated rats. These results suggest that the bladder C fiber afferent is also involved in modulating the micturition reflex caused by IVES.