| The number of spinal cord injury (SCI) patients in China has be more than 100 million and increased with a rate of 60,000 per year. Bladder dysfunction after SCI does not only affect the patient quality of life but also develop life-threatening complications, for example, renal failure. Electrical stimulation of the sacral nerves throng electrodes in the sacral foraminal (sacral neuromodulation, SNM) to modulate the neural circuits has become an effective and promising method for treating bladder dysfunctions invalid by the traditional treatment , especially spinal cord injured patients.The aim of this study was to investigate the effects of SNM on bladder dysfunction following complete SCI in rat as a reference for the clinical application SNM.The methods used in this sudty are as follows:First, to set a rat model with bladder dysfucntion following complete SCI. The adult female Sprague-Dawley rats (200-300g) are completely transected in the T9-T11 vertebra after laminectomy in general anesthesia. Following SCI, the bladder of rats was manually expressed once a day (Crede's maneuver). And the weight of expressed urine is used to reflect the residual volume and assess the recovery of bladder activity.Second, to compare the bladder pressure differences under different grades of bladder filling in 4 intact rats and 3 spinal cord injuried (SCI) rats. The rats were general anaesthetized and incised along the midline abdominal to expose the bladder, then a polyethylene tube (PE-60) for intact rat or a intravenous needle for SCI rat is inserted into the dome of the empty bladder to infuse saline with 37°C. The infusion rates are 0.05ml/min, 0.1ml/min, 0.2ml/min and 0.5ml/mim. At the same time the bladder pressure is recorded and analized finally.Third, to treat 7 SCI rats with SNM for 6 hours with the stimulation electrode placed in the S1 foramen unilaterally and the reference electrode placed 2-3 cm away under skin. Monophasic stimulus pulses with frequency of 20 Hz, pulse duration of 0.1ms, train duration of 30s, and train period of 180s were delivered to the electrodes. The stimulation amplitude was adjusted to 80% of the value which firstly induced a visible tail tremor. Before and after SNM treatment the bladder pressure under continuous infusion is recorded and analized.The main results in this study are as follows:First, after SCI surgery, the rat had paraplegia and urinary retention. The weight of urine expressed manually increases initially and reached to a peak at 1-week post-spinalization followed by a gradual decline. This maybe indicate that the function of spinal cord was coming back after shock period similar to clinlical symptoms. The survival rate of SCI rats was increased to 80% from 20% because of improved surgical techniques and postoperative care.Second, for intact rats, the bladder produced periodic complete voiding contractions, and the bladder contraction period were dependent on rates of bladder filling, while the bladder contraction duration and peak intravesical pressure were not sensitive to the infusion rates. For SCI rats, they showed uninhibited non-voiding contractions with increasing pressure baseline and a smaller void contraction at larger bladder volumes with high and sustained intravesical pressures. The bladder contractions in the SCI rats were not sensitive to the infusion rates, and bladder contraction period and peak pressure were much less than those in the intact rats.Third, with SNM treatment, bladder contraction period and duration were increased and reached peak value at 27 days post SCI surgery, and the peak intravesical pressure was decreased and reached the lowest value at 20 days post SCI surgery. Those changes indicated an improvement of bladder reflex function and the effect of SNM related with the time post SCI surgery.In this study, we find that the bladder of T9-T11 complete SCI rat model has similar clinical symptoms and could be used to study the effect of SNM. The bladder contraction activities in rat have changed after SCI and improved to some extent with SNM treatment for some hours. And the earlier SNM treatment after spinal shock, the better effect. This may be related with irreversible changes of bladder after SCI. |
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