Reflex activities of the urinary bladder in intact and spinally transected rats with bladder filling and sacral neuromodulation

The aim of this study was to investigate the bladder responses with different grades of bladder filling in intact and spinal cord injury (SCI) rats. The study also examined the effects of sacral neuromodulation (SNM) on bladder reflex responses in the rat model following complete SCI. Eight adult female Sprague Dawley rats were divided into three groups: group 1, intact rats (n=4); group 2, spinally transected (T9-T10) rats (n=4); group 3, spinally transected rats with SNM treatment (n=1). For group 3, the rats were treated by SNM for 6 hours with the cathode electrode placed in the S1 foramen unilaterally. The intravesical pressure induced by continuous infusion of saline with different grades under general anesthesia was recorded in all groups. The SCI rats displayed neurogenic detrusor overactivity characterized by non-voiding contractions during bladder filling. The bladder contractions in the SCI rats, unlike in the intact rats, were independent of the rate of bladder filling. With SNM, the peak intravesical pressure was increased, indicating an improvement of bladder reflex function. These data are discussed in the context of understanding the bladder reflex activity before and after SCI, as well as the effects with SNM.