Dynamics of the partial restoration of slow-wave frequency of the duodenum below transection.
Transection of the proximal duodenum of dogs was followed by end-to-end anastomosis. The electrical activity of the duodenal wall of both segments was recorded. On the background of decreased slow-wave frequency below the section single slow waves were observed with duration similar to that of the slow waves above the section. In the days after surgery their number increased, small groups of such waves appearing during and after spike activity. In some of the experiments from the end of the first month of the sixth month after surgery the slow wave frequency below the section approached the slow wave rhythm above the section as evidenced by the histograms. This was a temporary phenomen, which was partly eliminated by cholinergic and alpha- and beta-adrenergic antagonists. Such a phenomenon was also observed in definitively spearated distal segments of the duodenum. Histological examination of intestinal wall taken from the area of anastomosis showed on the 3rd day the presence of single smooth-muscle cells among the granulation tissue, filling the gap between the wound edges; on the 6th day the number of these cells increased and on the 9th and 12th day they formed small groups. From the end of the first month to the sixth month small sheaves of smooth-muscle cells were observed in the cicatricial tissue. It is concluded that the intrinsic nervous system keeps the slow wave frequency below the duodenal transection at a higher level than the smooth muscle cell regeneration might ensure.