The aim of this study was to compare the motor pattern (recorded as changes in intraluminal pressure) of isolated duodenum and proximal colon between dystrophic mdx and normal mice. When duodenal recordings from control preparations were compared with mdx mice there was no significant difference in the spontaneous motor pattern, responses to electrical nerve stimulation or sensitivity to pharmacological agents. Colonic segments from mdx mice showed a more complex motor pattern, consisting of contractions with amplitude and frequency similar to those of controls and by additional contractions with lower amplitude and higher frequency. Moreover, 70% of the colonic preparations from mdx mice developed active tone. TTX (1 microM), both in control and in mdx mice, changed the motor pattern, revealing regular rhythmic contractions similar in both preparations. L-NAME (100 microM) in both preparations increased contractile activity, revealing additional low contractions in control and potentiating them in mdx colon. In both control and mdx mice, inhibitory responses elicited by electrical field stimulation (EFS) were significantly attenuated by L-NAME. Our results provide evidence for the presence of a different motor pattern in mdx proximal colon and suggest that mdx mice can be considered a suitable animal model for investigating the dystrophic process.