PRESSOR RESPONSES TO DISTENSION OF THE URETER IN ANESTHETIZED RATS - CHARACTERIZATION OF A MODEL OF ACUTE VISCERAL PAIN

We have characterised presser responses to stimulation of the ureter i n anaesthetised rats (n = 20) as a model of acute visceral pain. The l eft ureter was cannulated close to the bladder and graded stimuli appl ied (5-90 mmHg, 30 s). The threshold was similar to 25 mmHg. Suprathre shold pressures evoked responses proportional to the stimulus intensit y, which were little altered when stimulation of the kidney was preven ted by ligation of the ureteric-pelvic junction. The stimulus response curve was dose-dependently attenuated by morphine (1-3 mg kg(-1) i.v. ), in a naloxone reversible manner. The characteristics of the respons es observed correlate well with pain sensation in man and with the pro perties of ureteric primary afferent neurones in animals.