RABBIT SPHINCTER OF ODDI AND DUODENAL PRESSURE AND SLOW-WAVE ACTIVITY- EFFECTS OF CHOLECYSTOKININ

Background: The presence of sphincter of Oddi (SO) slow waves has been noted in earlier studies on the effect of cholecystokinin (CCK) on th e SO, but a more thorough description of changes in SO slow-wave and p ressure activity induced by CCK is needed. Methods: The SO and duodenu m in anaesthetized rabbits were prepared with perfused catheters and b ipolar electrodes. Increasing, successive doses of CCK (1/32 to 1/1 Iv y Dog Units (IDU)/kg) were administered intravenously every 15th mint The digitized recordings were scored on a computer in control and stim ulatory CCK sequences. Results: CCK had a significantly stimulatory ef fect on SO and duodenum when estimated as area below pressure peaks (p < 0.001), but quantitatively, this effect did not differ in the two o rgans (p = 0.59). CCK significantly decreased SO slow-wave frequency ( p < 0.05), whereas a similar trend in duodenal slow-wave frequency fai led to reach statistical significance. Most pressure peaks recorded fr om the SO were associated with only one slow wave ('simple peaks'), bu t the incidence of broad, irregular peaks belonging to more than one s low wave ('complex peaks') was significantly higher in CCK sequences ( p < 0.02). Spectral analysis of SO pressure and slow-wave activity con firmed the dominating one-to-one relation between SO slow-wave and pre ssure peaks up to 1/4 IDU/kg, but also showed the disturbance caused b y the increasing number of complex peaks generated by doses of at leas t 1/2 IDU/kg. Conclusions: CCK increases SO and duodenal activity equa lly. Up to a CCK dose of 1/4 IDU/kg the SO slow-wave regulatory mechan ism is undisturbed, but higher doses lead to a fall in slow-wave frequ ency and qualitative changes in the relation between SO pressure and s low-wave activity.