EFFECT OF CHOLECYSTOKININ OCTAPEPTIDE AND SOMATOSTATIN ON THE MECHANICAL AND ELECTRICAL-ACTIVITY OF THE COLON OF CONSCIOUS DOGS

Intraluminal pressure and electrical activity of the colon of conscious dogs were recorded using silver bipolar electrodes and a pressure transducer. Two phases in the mechanogram of the transverse colon were observed: a quiescent phase (lack of contractions) lasting 12.05 +/- 0.54 min and a contractile phase lasting 14.46 +/- 0.88 min. The electrical activity was characterized by a quiescent phase (only slow waves in the electrogram) with a duration of 13.55 +/- 1.73 min. Groups of spike potentials bursting in the rhythm of the slow waves appeared during the activity phase lasting 15.60 +/- 2.02 min. Cholecystokinin octapeptide (CCK8) (10-20 ng/kg i. v.) significantly increased the duration of 1-3 active phases and shortened the duration of the quiescent phases. The percentage of slow waves with spike potentials during the active phase in the electrogram increased. Colonic contractions also increased, i.e. CCK8 evoked an enhanced motility of the colon. Somatostatin (1-2 mug/kg i.v.) increased by two to three times the duration of the quiescent phases. Atropine (50-100 mug/kg i.v.) or somatostatin (1-2 mug/kg i.v.) inhibited both the spontaneous and the CCK8-induced colonic motility. It is suggested that the inhibitory effect of somatostatin on spontaneous and CCK8-induced colonic activity in conscious dogs is mediated by a decrease in cholinergic neurotransmission.