The effect of duodenal and mid small bowel transection on the frequency gradient of the pacesetter potential in the canine small intestine

Abstract

SUMMARY1. The effect of surgical transection and reunion of the small bowel on its pacesetter potenial (PP) frequency gradient was studied over periods of 3 months in six conscious, healthy dogs, using fourteen platinum electrodes previously implanted along the bowel.2. Duodenal transection and reunion abolished the gradient of the pacesetter potential distal to the transection and this effect persisted throughout 3 months of observation.3. In dogs with two transections, one in the duodenum and another in the mid small bowel, the mid small bowel transection and reunion further reduced the frequency of the PP caudad to it and this effect also persisted throughout the 3 months of observation.4. We conclude that the gradient in intact bowel occurs because the frequency of the duodenal pace-maker is considerably more rapid than the natural frequency of the PP in the rest of the bowel, and because the bowel is composed of collections or populations of smooth muscle cells with differing natural or intrinsic PP frequencies arranged in a progression of diminishing frequencies from orad to caudad location. The natural frequency of a segment is unmasked by transection of the bowel just orad to it because this eliminates the influence or drive of the orad pace-maker. The findings are in agreement with the concept that in intact bowel, as the PP passes caudadward, distal populations of cells are eventually encountered which cannot follow the faster orad pacesetter because of the slowness of their natural frequency. Thus, during caudad passage, some cycles of the PP are not transmitted and this, occurring over the length of the bowel, accounts in part, at least, for the gradient of frequency of PP over the small bowel. CHARLES F. CODE AND JOSEPH H. SZURSZEWSKI

The Effects of Transections on the Basic Electrical Rhythm in the Canine Jejunum

“…In our experiments the transection was performed at 20 cm from the ligament of Treitz. The results are in agreement with those of C ode and Szurszewski [4] who made transections at about the same level. The effects of a sec ond transection, done caudally from the first one, are not clearly estab lished.…”

“…After the proximal transection, this frequency dropped to 12.0+0.4 cpm (p <0.05) and, after the distal transection, it dropped to 10.9+0.4 cpm (p <0.05). This last frequency change shows the influence of the distal intestine on the electrical behaviour of the jejunum.The intestinal smooth muscle exhibits an electrical activity consisting of spike potentials appearing on a slow wave often called 'basic electrical rhythm' (BER) [4]. The existence of a decreasing BER frequency gra dient is well established since the studies of A lvarez and Starkweather [1].…”

Electrophysiology of smooth muscle of the small intestine of some mammals.

“…The frequency of activity in each cell was obtained by determining the inter-slow-wave or burst interval during at least 10 min ofcontinuous recording. The mean frequency observed in vitro in this study corresponds well with the mean frequency recorded in vivo from the whole wall of the transacted small intestine (Code & Szurszewski, 1970).…”

Effects of Resection on the Electrical Slow Wave in Canine Jejunum

“…The question arises if reanastomosis will produce recoupling. The effects of immediate reunion of the intestine after transection have been studied, in vivo, in unanesthetized dogs [2,4,7,11,15,19]. There are some discrepancies among the obtained results.…”

“…The SW was found to become again fully coordinated at both sides of the anastomosis in the stomach [2], In the small bowel. Code and Szurszewski [7] found that the frequency reduction per sisted throughout the entire period of obser vation of 3 months. On the other hand.…”