Cecocolonic motility in the chicken. Effects of cholecystokinin

The aims of this work were 1) to define electromyographically the motility pattern of chicken ceca and colon; 2) to study the changes induced by photoperiod and food intake on the motility of this area and 3) to characterize the motor effects of intravenous (i.v.) cholecystokinin in vivo, measuring changes in electrical activity and intracecal pressure. Electromyographical studies show that in ceca, the spike burst frequency is higher during the day than during the night and in the fed than in the fasted state; about 90% of the bursts propagate towards the apex and corresponde to filling movements. In the colon the spike burst frequency during the day is 2.9 bursts/min in animals fed ad libitum. Nocturnal recordings in animals fed ad libitum and diurnal recordings in fasted animals show a significantly decreased electrical activity. Both CCK-8s and CCK-4 induce a dose-dependent decrease of colonic electrical activity and a dose-dependent increase in the number of colonic defecations. CCK-4 also causes a slight inhibition in the cecum, whereas CCK-8s induces an increase in cecal electrical activity. Intracecal pressure recordings performed in anaesthetized animals provide similar results. In conclusion, the cecocolonic motility of the chicken displays a circadian pattern and undergoes substantial modifications in the fed compared to the fasted state. CCK-8s is not mediating the increased colonic activity that follows food intake, as its effects on colonic motility are inhibitory. In contrast, i.v. CCK-8s induces defecation and a dose dependent increase in cecal electrical activity, intraluminal pressure and colonic defecation. Intravenous CCK-4 induces inhibitory effects both on ceca and colon.