Influence of papaverine on rat bladder contractions in vivo

In an acute rat model (in vivo) spontaneous rhythmic bladder contractions were induced by ligation of the urethra. In addition single bladder contractions were recorded during neurostimulation of the pelvic nerve. Spontaneous and electrically induced bladder contractions were sensitive to papaverine and isoprenaline in vivo. The basal bladder pressure and bladder contraction parameters were reduced more potently by isoprenaline. Blood pressure decreased significantly after isoprenaline injection (0.5-50 micrograms/kg = 4.73 x 10(-6)-4.73 x 10(-4) mol/l) and high concentration of papaverine (5 mg/kg = 2.95 x 10(-2) mol/l). Compared to isoprenaline papaverine was less toxic. These results are different to previous in vitro investigations in rat bladder strips. In vivo papaverine seems to be less effective on nerve-mediated bladder contractions and decreases bladder pressure. Our results indicate that beta-adrenergic receptors play a potent role in the inhibition of spontaneous and pelvic nerve-induced bladder contraction.