Induction of urethral closure and inhibition of bladder contraction by continuous magnetic stimulation

Magnetic stimulation has been considered to be a technique for stimulating nervous system noninvasively and it has been;used for experimental and clin ical testings on the central and peripheral nervous systems. However, comme rcially available magnetic stimulators can only discharge single pulses for less than several minutes because the coil soon overheats. We newly devise d a continuous magnetic stimulator assuring long-time stimulation, and this study was designed to confirm whether continuous magnetic stimulation woul d result in urethral closure and inhibition of bladder contraction in anest hetized canine models. Twelve female beagle dogs, weighing 9 to 12 kg, were anesthetized with a mi xture of alpha-chloralose and urethane. In six beagles, a 4 F microtip tran sducer was inserted transurethrally, and maximum intraurethral pressure was monitored. In the remaining six animals, urethra was ligated at the bladde r neck and a 4 F double lumen catheter was inserted from the dome of the bl adder to infuse physiological saline, monitoring isovolumetric rhythmic bla dder contraction: The stimulating coil, of which temperature was kept at 20 -25 degrees C by the built-in cooling system, was placed on the ishio-recta l fossa to stimulate the pudendal nerve at 10 Hz. The intraurethral pressur e increased by 69.1 +/- 27.8 cm H2O, and iso-volumetric rhythmic bladder co ntraction was inhibited during the stimulation with 80% (240 Joule) of maxi mum output. In conclusion, continuous magnetic stimulator was found effective for ureth ral closure and inhibition of bladder contraction. (C) 1999 Wiley-Liss, Inc .