Serio R, Mulè F, Postorino A
Dipartimento di Biologia cellulare e dello Sviluppo, Laboratorio di Fisiologia generale, Palermo, Italia.
Can J Physiol Pharmacol. 1995 Jan;73(1):79-84. doi: 10.1139/y95-011.
Using a single sucrose gap apparatus, experiments were performed to determine the involvement of nitric oxide (NO) in the generation of nonadrenergic, noncholinergic (NANC) inhibitory junction potentials in circular muscle of rat proximal colon. Inhibitors of NO synthase, N omega-nitro-L-arginine and its methyl ester, reduced the amplitude of the electrically evoked inhibitory junction potentials, without affecting membrane resting potential. Such an effect was stereospecific and it was prevented by L-arginine but not by D-arginine. Sodium nitroprusside induced a tetrodotoxin-resistant hyperpolarization, which was not affected by NO synthase inhibitors. Apamin reduced sodium nitroprusside induced hyperpolarization, as well as NANC inhibitory junction potentials, and alpha-chymotrypsin decreased the amplitude of electrical field stimulation evoked responses. Residual responses after NO synthase inhibitors or after alpha-chymotrypsin were further reduced by pretreatment with alpha-chymotrypsin or NO synthase inhibitors, respectively. These results suggest that, in rat colonic circular muscle, NO plays an important role in NANC inhibitory junction potential generation. However, another mechanism, peptidergic in nature, is also involved.
使用单一蔗糖间隙装置进行实验，以确定一氧化氮（NO）在大鼠近端结肠环形肌非肾上腺素能、非胆碱能（NANC）抑制性接头电位产生中的作用。NO合酶抑制剂Nω-硝基-L-精氨酸及其甲酯降低了电诱发抑制性接头电位的幅度，但不影响膜静息电位。这种作用具有立体特异性，L-精氨酸可阻止其发生，而D-精氨酸则不能。硝普钠诱导了一种对河豚毒素有抗性的超极化，该超极化不受NO合酶抑制剂的影响。蜂毒明肽降低了硝普钠诱导的超极化以及NANC抑制性接头电位，而α-糜蛋白酶则降低了电场刺激诱发反应的幅度。分别用α-糜蛋白酶或NO合酶抑制剂预处理后，NO合酶抑制剂或α-糜蛋白酶处理后的残余反应进一步降低。这些结果表明，在大鼠结肠环形肌中，NO在NANC抑制性接头电位的产生中起重要作用。然而，另一种本质上为肽能的机制也参与其中。
