RESUMO
The effects of tiropramide on the isolated detrusor and intravesical pressure of the bladder in situ in rats were compared with those of flavoxate, oxybutynin and terodiline. The IC50 values (x 10(-5) M) of tiropramide for carbachol (CCh)-, K+ (60 mM)-, Ba2+ (10 mM)-, and electrical stimulation-induced contractions were 3.6, 4.2, 5.8, and 2.9, respectively. The four antispasmodics used (2 and 4 mg/kg, i.v., each) abolished the rhythmic bladder contractions in situ in anesthesized rats. Of the four compounds, oxybutynin was most potent and no significant differences were observed between the inhibitory effects of tiropramide, flavoxate and terodiline. The administration of flavoxate (30 and 60 mg/kg) into the duodenum little influenced the rhythmic bladder contractions. Tiropramide, flavoxate, oxybutynin and terodiline (8 and 12 mg/kg, i.v., each) dose-dependently prolonged the time to the volume-evoked micturition reflex, and the activity of tiropramide was not statistically different from those of the other three antispasmodics. Under unilateral pelvic and bilateral hypogastric nerve transection, both of the contractions induced by electrical stimulation of the peripheral and central cut ends of the pelvic nerve were dose-dependently inhibited to the same extent by tiropramide and terodiline. These results suggest that the effects of tiropramide on the function of urinary bladder in rats may be mainly due to direct actions on the smooth muscle, and that tiropramide is more potent than flavoxate and less potent than oxybutynin and terodiline.