Stimulation of extrinsic sympathetic nerves differentially affects neurogenic motor activity in guinea pig distal colon.

The speed of pellet propulsion through the isolated guinea pig distal colon in vitro significantly exceeds in vivo measurements, suggesting a role for inhibitory mechanisms from sources outside the gut. The aim of this study was to investigate the effects of sympathetic nerve stimulation on three different neurogenic motor behaviors of the distal colon: transient neural events (TNEs), colonic motor complexes (CMCs), and pellet propulsion. To do this, segments of guinea pig distal colon with intact connections to the inferior mesenteric ganglion (IMG) were set up in organ baths allowing for simultaneous extracellular suction electrode recordings from smooth muscle, video recordings for diameter mapping, and intraluminal manometry.

TRPV1 and TRPM8 antagonists reduce cystitis-induced bladder hypersensitivity via inhibition of different sensitised classes of bladder afferents in guinea pigs.

Background And Purpose: Interstitial cystitis (=painful bladder syndrome) is a chronic bladder syndrome characterised by pelvic and bladder pain, urinary frequency and urgency, and nocturia. Transient receptor potential (TRP) channels are an attractive target in reducing the pain associated with interstitial cystitis. The current study aims to determine the efficacy of combination of TRP vanilloid 1 (TRPV1) and TRP melastatin 8 (TRPM8) channel inhibition in reducing the pain associated with experimental cystitis in guinea pigs.

The effects of loperamide on excitatory and inhibitory neuromuscular function in the human colon.

Background: In most animal species, opioids alter colonic motility via the inhibition of excitatory enteric motor neurons. The mechanisms by which opioids alter human colonic motility are unclear. The aim of this study was to describe the effects of loperamide on neuromuscular function in the human colon.

Mechanisms underlying initiation of propulsion in guinea pig distal colon.

Colonic motor complexes (CMCs) are a major neurogenic activity in guineapig distal colon. The identity of the enteric neurons that initiate this activity is not established. Specialized intrinsic primary afferent neurons (IPANs) are a major candidate.

Novel intrinsic neurogenic and myogenic mechanisms underlying the formation of faecal pellets along the large intestine of guinea-pigs.

Soft faecal material is transformed into discrete, pellet-shaped faeces at the colonic flexure. Here, analysis of water content in natural faecal material revealed a decline from cecum to rectum without significant changes at the flexure. Thus, pellet formation is not explained by changes in viscosity alone.

Motor patterns in the proximal and distal mouse colon which underlie formation and propulsion of feces.

Background: In herbivores, the proximal and distal colonic regions feature distinct motor patterns underlying formation and propulsion of fecal pellets, respectively. Omnivores, such as mice and humans, lack a similar clear anatomical transition between colonic regions. We investigated whether distinct processes form and propel content along the large intestine of a mouse (an omnivore).

Identification of neurogenic intestinal motility patterns in silver perch (Bidyanus bidyanus) that persist over wide temperature ranges.

Background: Fish are increasingly being utilized as a model species for genetic manipulation studies related to gastrointestinal (GI) motility. Our aim was to identify whether patterns of GI motility in fish and the mechanisms underlying their generation are similar to those recorded from mammals (including humans).

Methods: The entire intestine was removed from euthanized adult Silver Perch (n = 11) and lesioned at the midway point to obtain two equal lengths.

Characterization of alternating neurogenic motor patterns in mouse colon.

Background: Colonic motor complexes (CMCs) have been widely recorded in the large intestine of vertebrates. We have investigated whether in the smooth muscle, a single unified pattern of electrical activity, or different patterns of electrical activity give rise to the different neurogenic patterns of motility underlying CMCs in vitro.

Methods: To study differences of the CMCs between proximal and distal colon, we used a novel combination of techniques to simultaneously record muscle diameter and force at multiple sites along the whole mouse colon ex vivo.

Neural motor complexes propagate continuously along the full length of mouse small intestine and colon.

Cyclical propagating waves of muscle contraction have been recorded in isolated small intestine or colon, referred to here as motor complexes (MCs). Small intestinal and colonic MCs are neurogenic, occur at similar frequencies, and propagate orally or aborally. Whether they can be coordinated between the different gut regions is unclear.

Roles of three distinct neurogenic motor patterns during pellet propulsion in guinea-pig distal colon.

Key Points: Enteric neural circuits enable isolated preparations of guinea-pig distal colon to propel solid and fluid contents by a self-sustaining neuromechanical loop process. In addition there are at least three neural mechanisms which are not directly involved in propulsion: cyclic motor complexes, transient neural events and distal colon migrating motor complexes. In excised guinea-pig colon we simultaneously recorded high resolution manometry, video-imaging of colonic wall movements and electrophysiological recordings from smooth muscle, which enabled us to identify mechanisms that underlie the propulsion of colonic content.

Functional changes in low- and high-threshold afferents in obstruction-induced bladder overactivity.

Neural mechanisms of lower urinary tract symptoms in obstruction-induced bladder overactivity remain unclear. We made the first single unit recordings from different types of spinal afferents to determine the effects of bladder outlet obstruction in guinea pigs. A model of gradual bladder outlet obstruction in male guinea pigs was used to produce overactive bladder.

Identification of multiple distinct neurogenic motor patterns that can occur simultaneously in the guinea pig distal colon.

In the guinea pig distal colon, nonpropulsive neurally mediated motor patterns have been observed in different experimental conditions. Isolated segments of guinea pig distal colon were used to investigate these neural mechanisms by simultaneously recording wall motion, intraluminal pressure, and smooth muscle electrical activity in different conditions of constant distension and in response to pharmacological agents. Three distinct neurally dependent motor patterns were identified: transient neural events (TNEs), cyclic motor complexes (CMC), and distal colon migrating motor complexes (DCMMC).

Conscious voiding during bladder obstruction in guinea pigs correlates with contractile activity of isolated bladders.

Purpose: There are many hypotheses accounting for detrusor overactivity; however, the exact mechanisms are still incompletely understood. We used a model of bladder outlet obstruction in male guinea pigs as a way to produce detrusor overactivity. The objective was to determine whether changes in voiding of obstructed guinea pigs correlates with specific changes in contractile activity of their isolated bladders in vitro.