ABSTRACT
PURPOSE: Homozygous mutant Ncx/Hox11L.1-deficient (Ncx-/-) mice develop mega-ileo-ceco-colon with a caliber change in the proximal colon. This study investigated the mechanism of intestinal motility in these mice. METHOD: Five-week-old male and female Ncx-/- mice with mega-ileo-ceco-colon (n = 8) were compared with age-matched male BDF1 mice used as controls (n = 8). All mice were sacrificed, and uniform-sized strips of jejunum, ileum, proximal colon, and distal colon were exposed to electrical field stimulation and pretreatment with atropine sulfate, guanethidine, or tetrodotoxin. Contractile responses were recorded and compared. RESULTS: Longitudinal muscle from strips of jejunum and ileum from all mice (BDF1 and Ncx-/-) did not respond to electrical field stimulation, whereas ileal circular muscle contracted in BDF1 mice and contracted and relaxed in Ncx-/- mice. Pretreatment with atropine sulfate and guanethidine inhibited the responses of circular muscle of distal colon and ileum in BDF1 mice significantly (P < .05), but no effect was observed in Ncx-/- mice. CONCLUSION: In ileum, BDF1 mice have cholinergic and adrenergic dominant contraction patterns, whereas Ncx-/- mice have relaxation-dominant patterns because of nonadrenergic, noncholinergic nerves. Based on this, there would appear to be some kind of variation in the gastrointestinal nerve supply in Ncx-/- mice.
Subject(s)
Enteric Nervous System/pathology , Gastrointestinal Motility/genetics , Intestinal Diseases/physiopathology , Muscle, Smooth/innervation , Acetylcholine/pharmacology , Animals , Disease Models, Animal , Electric Stimulation , Female , Ganglia/drug effects , Gastrointestinal Motility/drug effects , Gastrointestinal Motility/physiology , Hirschsprung Disease/physiopathology , Homeodomain Proteins , Male , Mice , Mice, Inbred Strains , Mice, Neurologic Mutants , Muscle Contraction/drug effects , Muscle Contraction/physiology , Muscle, Smooth/physiology , Random Allocation , Reference Values , Sensitivity and Specificity , Statistics, Nonparametric , Submucous Plexus/physiologyABSTRACT
BACKGROUND/PURPOSE: Homozygous mutant Ncx/Hox11L.1-deficient (Ncx-/-) mice develop mega-ileo-ceco-colon (mega-ICC) with a caliber change in the proximal colon. The authors investigated the mechanism of intestinal dysmotility in these mice. METHODS: Five-week-old Ncx-/- mice with mega ICC were compared with age-matched BDF1 control mice. Jejunum, ileum, and colon were excised from all mice and 1.0-cm-long strips of each organ, each with a resting tension of 0.5g, were suspended in an organ bath filled with Tyrode's solution at 37 degrees C and bubbled with a mixture of 95% oxygen and 5% carbon dioxide. Contractile responses to acetylcholine chloride (ACh), histamine, serotonin, and barium chloride (BaCl2) were recorded isometrically. RESULTS: For ACh, Ncx-/- mice had decreased distal colon circular muscle contraction only at lower doses and decreased distal colon longitudinal muscle contraction for all doses compared with controls (P <.05 or P <.01). In the proximal colon, Ncx-/- mice had increased circular muscle contraction only at higher doses and decreased longitudinal muscle contraction only at lower doses compared with controls (P <.01 or P <.05). ACh did not affect jejunum, and there were no significant effects on ileum. There was no response to histamine and serotonin by any part of the bowel, and the response to BaCl2 was the same for both Ncx-/- mice and controls. CONCLUSIONS: Only ACh differentially affected muscle contraction in Ncx-/- mice in the proximal and distal colon. Thus, ACh is implicated in causing the bowel dysmotility seen in Ncx-/- mice and human IND.
Subject(s)
Acetylcholine/physiology , Gastrointestinal Motility/physiology , Hirschsprung Disease/etiology , Homeodomain Proteins/physiology , Muscle, Smooth/drug effects , Neurons/pathology , Submucous Plexus/abnormalities , Acetylcholine/pharmacology , Animals , Barium Compounds/pharmacology , Chlorides/pharmacology , Colon/drug effects , Dose-Response Relationship, Drug , Ganglia, Autonomic/abnormalities , Ganglia, Autonomic/pathology , Gastrointestinal Motility/drug effects , Genes, Homeobox , Hirschsprung Disease/genetics , Hirschsprung Disease/pathology , Hirschsprung Disease/physiopathology , Histamine/pharmacology , Homeodomain Proteins/genetics , Ileal Diseases/congenital , Ileal Diseases/etiology , Ileal Diseases/genetics , Ileal Diseases/pathology , Ileal Diseases/physiopathology , Ileum/drug effects , Jejunum/drug effects , Mice , Mice, Inbred C57BL , Mice, Inbred DBA , Mice, Knockout , Muscle Contraction/drug effects , Muscle, Smooth/physiopathology , Serotonin/pharmacology , Submucous Plexus/pathologyABSTRACT
Effects of geissoschizine methyl ether, an indole alkaloid isolated from the hook of Uncariae Ramulus et Uncus, on vascular responses were examined using isolated strips of rat aorta. Geissoschizine methyl ether (10(-7)-10(-4) M) relaxed norepinephrine (5x10(-8) M)-induced contraction in a dose-dependent manner. The potency (50% efficacy concentration, EC(50)=0.744 microM) was approximately 14 times greater than that (EC(50)=10.6 microM) of hirsutine, one of the indole alkaloids isolated from Uncariae Ramulus et Uncus that demonstrates a vasorelaxant effect by Ca(2+)-channel blocking. The vasorelaxant effect of geissoschizine methyl ether found at the lower concentrations (10(-7)-3x10(-6) M) on the norepinephrine-induced contraction was abolished by pretreatment with N(G)-nitro-L-arginine (10(-4) M), an inhibitor of nitric oxide synthesis, or by denuding aortas of endothelium, while the effects at the higher concentrations (10(-5)-10(-4) M) were not completely prevented by either N(G)-nitro-L-arginine and deendothelialization. Furthermore, geissoschizine methyl ether did not relax high K(+)-, Ca(2+)- and a Ca(2+)-channel agonist Bay K8644-induced contractions at the lower concentrations that markedly relaxed the norepinephrine-induced contractions, while the higher concentrations of geissoschizine methyl ether relaxed the high K(+)-, Ca(2+)- and Bay K8644-induced contractions. These results suggest that the vasorelaxant effect of geissoschizine methyl ether is composed of two different mechanisms: endothelial dependency with nitric oxide and endothelial independency with voltage-dependent Ca(2+)-channel blocking.
