Rapid evaluation of the efficacy of pharmacologic agents and their analogs in enhancing bladder capacity and reducing the voiding frequency.

We report here the results of a simplified screening method to rapidly compare the pharmacologic action of drugs relevant to the urinary tract. This method avoids the use of anesthesia and of external infusion into the bladder relying on the physiological stimulation of the volume-evoked micturition reflex (VEMR) by diuresis. Mature female rats weighing 240-310 g were placed in restrainer cages that afforded access to food and water but limited movement. Under the rear of the rat, a collecting funnel and weight measuring device was secured. For each VEMR, the weight of the volume voided was recorded on a polygraph which also provided a record of the time of voiding. To evaluate the relative pharmacologic efficacy of the drug under study, 1 mg/kg furosemide along with the drug to be evaluated was diluted in 5 ml of saline and injected subcutaneously. Rats received approximately equimolar concentrations of thiphenamil and 15 other analogs, Ca2+ channel blockers, and K+ channel openers. The furosemide was given to obtain a controlled level of diuresis and avoid the effects of circadian variations in urine flow. Parameters considered were 1) mean volume voided per VEMR, 2) frequency, 3) output, and 4) latency. This model allows the rapid evaluation of drugs designed to increase bladder capacity and decrease the frequency of voiding, and it is particularly useful in evaluating the relative efficacy of drugs that are chemical analogs.