A Possible Role of Nitric Oxode in The Relaxations Induced by Electrical Field Stimulation of Isolated frog Oesophageal Strips

Electrical field stimulation (EFS) caused voltage dependent relaxations in the isolated frog upper oesophageal circular segments precontracted with carbachol (CCh). The influence of NG-nitro L-arginine (L-NOARG) on these relaxations was investigated. 10-6 M, 10-5 M, 5x10-5 M and 10-4 M concentrations of this substance inhibited them in a dose dependent manner. 4x10-4 M L-arginine (L-ARG) prevented the inhibitory action of 5x10-5 M and 10-4 M L-NOARG while 4x10-4 M D-arginine (D-ARG) did not protect against the effect of L-NOARG. Neither L-ARG nor D-ARG had any significant effects on the electrically-induced
relaxations. The results suggested that nitric oxide (NO) is involved in the relaxations induced by EFS possibly mediated by non adrenergic non cholinergic (NANC) nerves.