排尿反射時の内尿道括約筋弛緩反応における nitric oxide の作用に関する実験的研究

: Effects of L-arginine and the inhibitors of nitric oxide/cyclic GMP pathway on the internal urethral relaxation were examined in anesthetized rats. The bladder pressure and internal urethral pressure were continuously recorded during the rhythmic bladder contractions before and after intraarterial administration of the following drugs. Used drugs were L-arginine from which nitric oxide is synthesized, NG-monomethyl-L-arginine (L-NMMA), NG-nitro-L-arginine methyl ester (L-NAME) which inhibit the synthesis of nitric oxide from L-arginine, and methylene blue which inhibits the activation of soluble guanylyl cyclase. In anesthetized rats, rhythmic bladder contractions with concomitant urethral relaxations were occurred. Administration of L-arginine (30 mg/kg, i.a.) produced a decrease in the internal urethral pressure. Administration of L-NMMA (3-30 mg/kg, i.a.), L-NAME (3-10 mg/kg, i.a.), and methylene blue (3-30 mg/kg, i.a.) produced an inhibition of the relaxations of the internal urethral sphincter during rhythmic bladder contractions. Present study suggests that nitric oxide/cyclic GMP pathway takes an important role for the relaxation of the internal urethral sphincter during rhythmic bladder contractions.