Role of somatostatin neurons in intestinal peristalsis: facilitatory interneurons in descending pathways.
The role of somatostatin neurons in the regulation of peristalsis was examined in segments of rat colon that permit separate characterization of the ascending contraction and descending relaxation components of the peristaltic reflex. Release of somatostatin and vasoactive intestinal peptide (VIP) increased significantly only during descending relaxation. Preincubation of the segment with somatostatin antiserum (final concentration 1:40) decreased VIP release and descending relaxation. Addition of somatostatin (1 nM to 1 microM) augmented VIP release and descending relaxation in a concentration-dependent manner. Together the results implied that the increase in somatostatin release was coupled to, and responsible for, the increase in VIP release, which in turn was responsible for descending relaxation. The results are consistent with the topography of myenteric VIP neurons (which project into circular muscle) and somatostatin neurons (which project caudad within the plexus) and the pharmacological properties of the two peptides. Somatostatin antiserum had no effect on basal VIP release or ascending contraction, indicating that somatostatin neurons were not involved in the regulation of ascending contraction. The study suggests that somatostatin neurons of the myenteric plexus act as facilitatory interneurons in descending pathways.
D000818:Animals; D003106:Colon / Q000294:innervation*; D004305:Dose-Response Relationship, Drug; D005769:Gastrointestinal Motility; D007106:Immune Sera; D009474:Neurons / Q000166:cytology*; D051381:Rats; D012016:Reference Values; D013004:Somatostatin / Q000276:immunology / Q000502:physiology*; D014660:Vasoactive Intestinal Peptide / Q000378:metabolism
D007106:Immune Sera; D014660:Vasoactive Intestinal Peptide; D013004:Somatostatin