BACKGROUND: Nitric oxide acts as a non-adrenergic and non-cholinergic neurotransmitter in the bladder and urethra. It activates the guanilatocyclase that transforms GMP in cGMP which promotes muscle relaxation. Sildenafil citrate increases the cGMP concentration by inhibiting the phosphodiesterase responsible for its hydrolysis. METHODS: 6 female rats weighing 200g were anesthetized with urethane at a dosage of 1.25mg/kg. All animals underwent cystostomy with a catheter P50 connected by a Y to an infusion pump and to a polygraph Narco-Biosystem. The cystometry was performed trice in each animal: right after the cystostomy, after surgical of bladder denervation and 1h after gastric infusion of 1mg/kg of sildenafil citrate. Maximum (MaP) and minimum (MiP) vesical pressure were compared in the following moments: I - before bladder denervation, II - after bladder denervation and III - after bladder denervation and sildenafil administration. Wilcoxon test was used for a level of significance of 5%. RESULTS: Mean values of MaP were: I - 86.6±10.1, II - 42.6±15.0 and III - 30.8±12.4. The corresponding values of MiP were: : I - 72.1±18.9, II - 31.1±9.8 and III - 14.5±9.5. The comparison between MaP and MiP in each moment showed difference only in moment III (p<0.01). For MaP p value was <0.002 in IxII and IxIII and >0.05 in IIxIII. For MiP the p values were <0.004 in IxII, <0.002 in IxIII and <0.01 in IIxIII. CONCLUSION: 1) Bladder denervation reduces maximum and minimum urethral pressure; 2) Sildenafil citrate reduces the minimum urethral pressure widening the interval between the peak and bottom pressures; and, 3) Sildenafil citrate does not interfere on the peak urethral pressure after bladder denervation.
Sildenafil citrate; Denervation; Urethra; Bladder; Urodynamics
