An ultrasonographic method for the evaluation of dexmedetomidine on micturition in intact rats.

We describe a simple, noninvasive, nontraumatic, and reproducible ultrasonographic method to determine the effect of the alpha 2-adrenoceptor agonist dexmedetomidine in anesthetic dose (300 micrograms/kg subcutaneously) on the micturition reflex in intact rats. The bladder volumes were estimated by an ellipsoid equation. To validate the reliability of the method, an in vitro model assessment also was performed. The mean difference between estimated and instilled volumes were 27.3 microL (-21.61, 76.23). The highly significant correlation (r = 0.98, p < .001) indicates that the ultrasonography with the equation is a reliable tool. After the dexmedetomidine administration to intact rats, urine dribbling occurred at 30 +/- 4.8 min. The volume threshold for urination was 2100 +/- 100 microL. Although dribbling of the urine was observed almost continuously, significant differences were not observed between bladder volumes obtained at any time (from 10 to 100 min). This study indicates that the alpha 2-adrenoceptor agonist dexmedetomidine inhibits the micturition reflex in intact rats. The method described, which is both noninvasive and nonpainful, may therefore be widely used to quantify in small animals pharmacological effects on the urinary bladder.