Migration of the myoelectric complex after interruption of the myenteric plexus: Intestinal transection and regeneration of enteric nerves in the guinea pig

Abstract

The effects of surgical interruption of the myenteric plexus (myectomy), extrinsic denervation of a length of small intestine, or transection and reanastomosis of the intestinal wall on migration of phase III of the migrating myoelectric complex was studied in guinea pigs. In addition, the recovery of phase III migration and the regrowth of intestinal nerves and muscle across the reanastomosis was studied at various times up to 60 days after surgery. At 6–9 days after surgery, phase III did not migrate past the myectomy during 50%–60% of recorded migrating myoelectric complexes and transection and reanastomosis of the intestinal wall blocked aboral progression of phase III in 90% of cases. Extrinsic denervation did not alter phase III migration through the denervated segment. Phase III migration past the reanastomosis recovered with time after surgery; 80% recovery occurred by 60 days after surgery. Immunoreactivities for vasoactive intestinal peptide, gastrin-releasing peptide, and somatostatin were used as markers for intestinal nerves that were cut by transection. Immunoreactivities for vasoactive intestinal peptide and gastrinreleasing peptide are contained in myenteric neurons that project in an oral to anal direction to other myenteric ganglia and to the circular muscle. Immunoreactivity for somatostatin is contained in nerve fibers projecting aborally to other myenteric ganglia. At 7–15 days after surgery, there were accumulations of immunoreactivities for vasoactive intestinal peptide, gastrin-releasing peptide, and somatostatin in nerve fibers on the oral side of the reanastomosis, but nerve fibers containing these peptides were not observed in myenteric ganglia or circular muscle close to the anal edge. At 23–28 days, immunoreactivities for vasoactive intestinal peptide, gastrin-releasing peptide, and somatostatin nerve fibers were traced across the reanastomosis and nerve terminals were detected in ganglia and muscle close to the lesion on the anal side. Nerve fibers traversed the lesion in all cases at 57–60 days and vasoactive intestinal peptide-, gastrin-releasing peptide-, and somatostatin-immunoreactive nerve terminals were detected in the first two to three rows of myenteric ganglia on the anal side. Regrowth of intestinal muscle followed a similar timecourse to that observed for nerves. These data suggest that interruption of the myenteric plexus alone does not completely block phase III migration. In addition, recovery of phase III migration past a reanastomosis is associated with a restoration of both nervous and mechanical connections.