Objectives: 

To characterize the possible changes in the peristaltic propulsion in the distal colon of guinea pig and the underlying mechanisms.

Materials: 

Peristalsis was assessed by measuring the speed (mm/sec) of video recorded propulsion of artificial pellets in segments of guinea pig distal colon pinned in a sylgard-coated horizontal organ bath with constant perfusion. Guinea pigs were divided in two groups: young (age 3-6 months) and old (24-30 months). The effect of drugs was expressed as percentage change respect the previous resting state. Contractility of colon muscle strips was studied in organ bath. Significance was assessed by paired or unpaired t test as required.

Results: 

In the resting condition, peristaltic propulsion of pellets was significantly faster in aged than in young animals. This was in keeping with the finding in organ bath experiments that the cholinergic contractility, responsible for force generation in the oral limb of the peristaltic reflex, is significantly enhanced in aged colon. Inhibition of nitrergic neurotransmission with L-NAME accelerated significantly the propulsion in aged but not in young colon. A similar pattern was observed in response to treatment with MRS2179, a selective antagonist of the relaxant P2Y receptors. These results suggest that in aged colon the peristaltic reflex can be under nitrergic and purinergic inhibitory influences. Paradoxically, aging decreases the direct inhibitory effect of ATP treatment on propulsion.

Conclusions: 

Aging accelerates the propulsive peristalsis of guinea pig colon likely associated to an enhanced cholinergic contractility. Paradoxically, the aging process in this tissue involves a predominant inhibitory nitrergic innervation that would favor propulsion.

Supported by BFU2011-24365, RETICEF, ISCII, GR10009-JEX, FEDER.