Effects of cathodal trans-spinal direct current stimulation on lower urinary tract function in normal and spinal cord injury mice with overactive bladder

Objective. Lower urinary tract (LUT) dysfunction is a monumental problem affecting quality of life following neurotrauma, such as spinal cord injury (SCI). Proper function of the bladder and its associated structures depends on coordinated activity of the neuronal circuitry in the spinal cord and brain. Disconnection between the spinal and brain centers controlling the LUT causes fundamental changes in the mechanisms involved in the micturition and storage reflexes. We investigated the effects of cathodal trans-spinal direct current stimulation (c-tsDCS) of the lumbosacral spine on bladder and external urinary sphincter (EUS) functions. Approach. We used cystometry and electromyography (EMG), in mice with and without SCI. Main results. c-tsDCS caused initiation of the micturition reflex in urethane-anesthetized normal mice with depressed micturition reflexes. This effect was associated with normalized EUS-EMG activity. Moreover, in urethane-anesthetized normal mice with expressed micturition reflexes, c-tsDCS increased the firing frequency, amplitude, and duration of EUS-EMG activity. These effects were associated with increased maximum intravesical pressure (P-max) and intercontraction interval (ICI). In conscious normal animals, c-tsDCS caused significant increases in P-max, ICI, threshold pressure (P-thres), baseline pressure (P-base), and number and amplitude of non-voiding contractions (NVCnumb and P-im, respectively). In conscious mice with severe contusive SCI and overactive bladder, c-tsDCS increased P-max, ICI, and P-thres, but decreased P-base, NVCnumb, and P-im. c-tsDCS reduced the detrusor-overactivity/cystometry ratio, which is a measure of bladder overactivity associated with renal deterioration. Significance. These results indicate that c-tsDCS induces robust modulation of the lumbosacral spinal-cord circuitry that controls the LUT.