Aim: 

To investigate age-related changes in colonic contractility and to assess the possible benefits of melatonin treatment.

Methods: 

Colonic contractility was assessed by isometric tension recordings in circular orientated mucosa-free strips from proximal and distal mouse colon. Young (3 months old) and senescent (22-24 months old) mice were used in the study. A group of senescent animals was treated with melatonin (10 mg/Kg/day) for 6 months. In every strip 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: 

Aging reduced the myogenic responses to both KCl and bethanechol (60 and 70% of reduction, respectively). EFS induced a sustained relaxation followed by a rebound contraction (OFF response) that was frequency-dependent. Aging reduced the OFF contractions in both proximal and distal colon. The cholinergic and nitrergic components of these contractions were decreased in old animals, especially in distal colon, suggesting an age-dependent reduction in cholinergic and nitrergic nerves. In addition, in old animals, sensitive contractile nerves collaborate in the motor response, which could be the result of a subjacent chronic inflammation. Melatonin normalized the cholinergic contribution, reduced the sensitivity of afferent fibers and consistently restored neuromuscular function. The parallel improvement in agonist-induced responses can collaborate in the general improvement of colonic motor activity induced by the hormone.

Conclusion: 

Melatonin treatment restored colonic contractility, which supports its use to palliate age-related colonic dysfunctions.

Supported by BFU2007-60563 & RETICEF