Prostaglandin E₂: Actions on the Circular and Longitudinal Contractions of the Canine Colon

Abstract

The effect of prostaglandin E₂ (PGE₂) on the circular and longitudinal contractions of the canine colon was studied in chronic conditions. A mechanical transducer capable of recording simultaneously the variations of length in two perpendicular directions at 90° to each other was developed and implanted on the canine colon 10 cm distal to the ileocaecal junction. The recording sessions started on the 6th postoperative day. The colonic motility was recorded two hours before (control period) and two hours after the intravenous injection of PGE₂ in three different doses (0.1, 1.0 and 10 µg/kg). Two sorts of mechanical activity were identified: contractile phases (mean duration: 8.8 min for longitudinal and 6.7 min for circular contractions) and sporadic contractions (mean duration: 0.37 min for longitudinal and 0.28 min for circular contractions).

PGE₂ in the three different doses used induces an important reduction in the duration and in the amplitude of the circular contractions. These reductions become important only in the 2nd hour after the injection of PGE₂. The duration of the longitudinal contractions was modified by 10 µg/kg of PGE₂, provoking an important and immediate increase of this value. Although the amplitude of longitudinal contractions remains constant, each dose of PGE₂ induces strong premature bursts of longitudinal colonic contractions.

It is concluded that PGE₂ has a regulating effect on colonic motility, even at small doses, with a different action on the two muscular layers. According to the dose used, it leads to hypokinesia (relaxation) in the circular and to strong contractions in the longitudinal colonic muscles.

Correspondence