Cholinergic giant migrating contractions in conscious mouse colon assessed by using a novel noninvasive solid-state manometry method: modulation by stressors

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Abstract
There is a glaring lack of knowledge on mouse colonic motility in vivo, primarily due to unavailability of adequate recording methods. Using a noninvasive miniature catheter pressure transducer inserted into the distal colon, we assessed changes in colonic motility in conscious mice induced by various acute or chronic stressors and determined the neurotransmitters mediating these changes. Mice exposed to restraint stress (RS) for 60 min displayed distal colonic phasic contractions including high-amplitude giant migrating contractions (GMCs), which had peak amplitudes >25 mmHg and occurred at a rate of 15–25 h−1 of which over 50% were aborally propagative. Responses during the first 20-min of RS were characterized by high-frequency and high-amplitude contractions that were correlated with defecation. RS-induced GMCs and fecal pellet output were blocked by atropine (0.5 mg/kg ip) or the corticotrophin releasing factor (CRF) receptor antagonist astressin-B (100 μg/kg ip). RS activated colonic myenteric neurons as shown by Fos immunoreactivity. In mice previously exposed to repeated RS (60 min/day, 14 days), or in transgenic mice that overexpress CRF, the duration of stimulation of phasic colonic contractions was significantly shorter (10 vs. 20 min). In contrast to RS, abdominal surgery abolished colonic contractions including GMCs. These findings provide the first evidence for the presence of frequent cholinergic-dependent GMCs in the distal colon of conscious mice and their modulation by acute and chronic stressors. Noninvasive colonic manometry opens new venues to investigate colonic motor function in genetically modified mice relevant to diseases that involve colonic motility alterations.

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