title: Ascending excitatory neural pathways modulate slow phasic myogenic contractions in the isolated human colon.
abstract: BACKGROUND
  In animal models, enteric reflex pathways have potent effects on motor activity; their roles have been much less extensively studied in human gut. The aim of this study was to determine if ascending excitatory interneuronal pathways can modulate spontaneous phasic contractions in isolated preparations of human colonic circular muscle.
  
  
  METHODS
  Human colonic preparations were cut into T shapes, with vertical bar of the 'T' pharmacologically isolated. Electrical stimulation and the nicotinic agonist, 1,1-dimethyl-4-phenylpiperazinium iodide (DMPP), were applied to the isolated region and circular muscle contractile activity was measured from the cross-bar of the T, more than 10 mm orally from the region of stimulation.
  
  
  RESULTS
  The predominant form of spontaneous muscle activity consisted of tetrodotoxin-resistant, large amplitude, slow phasic contractions (SPCs), occurring at average intervals of 124 ± 68 s. Addition of a high concentration of hexamethonium (1 mmol L(-1)) to the superfusing solution significantly increased the interval between SPCs to 278.1 ± 138.3 s (P < 0.005). Focal electrical stimulation more than 10 mm aboral to the muscle recording site advanced the onset of the next SPC, and this effect persisted in hexamethonium. However, the effect of electrical stimulation was blocked by tetrodotoxin (TTX, 1 μmol L(-1)). Application of the nicotinic agonist DMPP (1 mmol L(-1)) to the aboral chamber often stimulated a premature SPC (n = 4).
  
  
  CONCLUSIONS
  The major form of spontaneous contractility in preparations of human colonic circular muscle is SPCs, which are myogenic in origin. Activation of ascending excitatory neural pathways, which involve nicotinic receptors, can modulate the timing of SPCs and thus influence human colonic motility.
authors: Discipline of Human Physiology, Flinders Medical Science and Technology, Flinders University, Adelaide, South Australia, Australia.
authors: S E
authors: SE
authors: Carbone
authors: P G
authors: PG
authors: Dinning
authors: M
authors: M
authors: Costa
authors: N J
authors: NJ
authors: Spencer
authors: S J H
authors: SJ
authors: Brookes
authors: D A
authors: DA
authors: Wattchow
mesh_terms: D000368:Aged; D003106:Colon / Q000294:innervation* / Q000502:physiology*; D004558:Electric Stimulation / Q000379:methods; D005260:Female; D005769:Gastrointestinal Motility / Q000502:physiology*; D006801:Humans; D008297:Male; D008875:Middle Aged; D009119:Muscle Contraction / Q000502:physiology*; D009130:Muscle, Smooth / Q000294:innervation / Q000502:physiology; D009434:Neural Pathways / Q000502:physiology; D009924:Organ Culture Techniques; D013997:Time Factors
keywords: excitatory neurotransmission; human colon; motility