Aim: 

To elucidate whether colonic mucosa may influence mouse colonic motility and the effects of aging.

Methods: 

Colonic contractility was assessed by isometric tension recordings in circular orientated strips from proximal and distal colon. Young (3 months old) and senescent (22-24 months old) mice were used in the study. The following preparations were used: (i) full-thickness strips (ii) muscle strips without mucosa and (iii) muscle strips without mucosa and submucosa (myenteric preparation). Spontaneous phasic and KCl- and bethanechol-induced contractions were registered. Intrinsic nerve-induced contractions were elicited by electrical field stimulation (EFS, 0.3 ms, 350 mA, 0.5-25 Hz, for 10 s every 3 min).

Results: 

The presence of mucosa reduced the frequency but increased the amplitude of spontaneous colon activity. In adult animals, the presence of the mucosa reduced KCl-and bethanechol-induced contractions (KCl: 88 and 93%; bethanechol: 79 and 91% of reduction in proximal and distal strips, respectively). The mucosa also inhibited smooth muscle contraction induced by EFS. When myenteric strips were incubated with mucosa there was a reduction in the responses to the agonists, suggesting the release of an inhibitory factor. In full-thickness strips, pre-treatment with indomethacin, L-NAME and TTX improved contractility in some specimens. In senescent mice, the mucosa exerted weaker inhibitory effects, which were only significant in distal colon.

Conclusion: 

Our data suggest an inhibitory role of the mucosa in colonic motility. Aging impairs these negative influences, which would be a protective mechanism taking into account the decreased contractility of aged colon.

Supported by BFU2007-60563 and RETICEF.