Colonic formation of soft feces in rabbits: a role for endogenous prostaglandins.

Rabbits produce hard and soft feces in a circadian rhythm. The motor activity of the haustrated proximal colon is inhibited during the formation of soft feces, whereas the spiking activity of the distal colon is stimulated. A potential role for endogenous prostaglandins (PG) in the control of the soft-feces elaboration by the rabbit colon was investigated in conscious animals by using PGE2 and PGF2 alpha and by inhibiting them with indomethacin. The infusion of both PGE2 and PGF2 alpha induced typical electromechanical events consisting of inhibition of the proximal and stimulation of the distal colon and was followed by soft-pellet defecation. Rabbits accustomed to be fed twice daily produced soft feces at fixed intervals of 252 +/- 32 min after the evening meal, with a soft-to-hard feces ratio of 1.45. After indomethacin treatment, this ratio was significantly (P less than 0.01) reduced to 0.92. These results are consistent with the concept that endogenous prostaglandins play a major role in the motor function involved in soft-feces formation by the rabbit.