Different modulation of spontaneous activities by nitrergic inhibitory nerves between ileum and jejunum in W/Wv mutant mice

We compared the spontaneous electrical and mechanical activities between the jejunum and ileum in the W/Wv mutant mouse, where ICC in the myenteric region (ICC-MY) are deficient. Electrical slow waves (SWs) superimposed with spike potentials, and synchronous circular and longitudinal muscle mechanical activities at a regular rhythm under ∼ 1 cm H2O were recorded in the jejunum and ileum of wild-type mice. However, in the jejunum and ileum of W/Wv mice, irregular electrical and mechanical activities without discernable SWs were recorded. N-nitro-l-arginine methyl ester (l-NAME) significantly decreased the mean interval of longitudinal muscle contractions from 4.43 ± 3.39 to 2.50 ± 1.23 s in the ileum of W/WV mice. l-NAME also significantly decreased mean coefficient of variance (decreased irregularity) in the intervals from 2.59 ± 0.84 to 0.48 ± 0.46 in the ileum. Tetrodotoxin also significantly decreased mean interval and coefficient of variance in the ileum. Neither l-NAME nor tetrodotoxin affected contractile activity in the jejunum. These results suggest that enteric nitrergic nerves in the ileum, but not the jejunum, mediate a steady-state inhibition of myogenic activity in W/Wv mice.