The effect of arylazido aminopropionyl ATP (ANAPP3) on inhibition of pelvic nerve evoked contractions of the cat urinary bladder.

Previously reported work has provided evidence that arylazido aminopropionyl ATP (ANAPP3), a P2-receptor antagonist, blocks the effects of ATP and other purine analogs, in the urinary bladder of the cat. This antagonism appeared limited to those effects mediated by P2-receptors, such as contraction of the urinary bladder. However, it was noted that ANAPP3 did alter the effects of adenosine, mediated through P1-receptors, in some preliminary experiments. A series of experiments was undertaken to determine if ANAPP3 blocks the P1-receptors and/or has effects on inhibition of bladder contractions. The urinary tract of anesthetized cats was exposed by a midline abdominal incision. The pelvic and hypogastric nerves were isolated and prepared for electrical stimulation. Bladder contractions were induced by stimulation of the pelvic nerves every 30 s with square wave pulses. These contractions were inhibited by hypogastric nerves and the exogenous administration of ATP, noradrenaline, adenosine or beta,gamma-methylene ATP (APPCP), a hydrolysis resistant analog of ATP. ANAPP3 (0.5 mumol, i.a.) was administered, but it did not antagonize the inhibition induced by any of the exogenously administered agents or hypogastric nerve stimulation. This study indicates that ANAPP3 is specific for P2-receptors and is not an effective antagonist of P1-receptors, at least in the urinary tract of the cat.