Urodynamic evaluation and electrical and pharmacologic neurostimulation. The rat model.

We introduce a rat model that allows simultaneous or independent recording of bladder and sphincteric activity. Via a polyethylene tube inserted into the bladder dome, bladder pressure is measured in response to constant intravesical saline perfusion. The electrical activity of the intra-abdominal urethra (a well-defined striated muscular tube which, in the rat, constitutes the external urethral sphincter) is recorded simultaneously with an electromyography needle electrode. Thus, precise statements can be made about detrusor/sphincter interrelationships. Changes in urodynamic parameters with the anesthetics urethane, methoxyflurane (Metofane), and thiobutabarbital sodium (Inactin) were investigated. High-frequency oscillations in intraluminal bladder pressure could be demonstrated during micturition cycles only in rats anesthetized with urethane or Metofane. As this high-frequency activity is generated by the striated muscle of the intra-abdominal urethra, the external sphincter of the rat is the force behind urine expulsion. The anesthetic Inactin combined with a low intravesical perfusion rate attenuated spontaneous bladder and sphincteric activity and abolished micturition cycles. This rat model can provide accurate and reproducible measurements of urodynamic changes in response to electrical stimulation of the pelvic and pudendal nerves and pharmacologic stimulation with neuropeptides at the lumbosacral spinal cord level. We recommend using this model with urethane or Metofane for physiologic studies of micturition and with Inactin for meticulous neuropharmacologic and electrostimulatory evaluation of urodynamic parameters.