URODYNAMIC EVALUATION AND ELECTRICAL AND PHARMACOLOGICAL NEUROSTIMULATION - THE RAT MODEL

We introduce a rat model that allows simultaneous or independent recor ding of bladder and sphincteric activity. Via a polyethylene tube inse rted into the bladder dome, bladder pressure is measured in response t o constant intravesical saline perfusion. The electrical activity of t he intra-abdominal urethra (a well-defined striated muscular tube whic h, in the rat, constitutes the external urethral sphincter) is recorde d simultaneously with an electromyography needle electrode. Thus, prec ise statements can be made about detrusor/sphincter interrelationships . Changes in urodynamic parameters with the anesthetics urethane, meth oxyflurane (Metofane), and thiobutabarbital sodium (Inactin) were inve stigated. High-frequency oscillations in intraluminal bladder pressure could be demonstrated during micturition cycles only in rats anesthet ized with urethane or Metofane. As this high-frequency activity is gen erated by the striated muscle of the intra-abdominal urethra, the exte rnal sphincter of the rat is the force behind urine expulsion. The ane sthetic Inactin combined with a low intravesical perfusion rate attenu ated spontaneous bladder and sphincteric activity and abolished mictur ition cycles. This rat model can provide accurate and reproducible mea surements of urodynamic changes in response to electrical stimulation of the pelvic and pudendal nerves and pharmacologic stimulation with n europeptides at the lumbosacral spinal cord level. We recommend using this model with urethane or Metofane for physiologic studies of mictur ition and with Inactin for meticulous neuropharmacologic and electrost imulatory evaluation of urodynamic parameters.