Luminal stimuli acutely sensitize visceromotor responses to distension of the rat stomach

Open source timed pressure control hardware and software for delivery of air mediated distensions in animal models

Studying the visceral sensory component of peripheral nervous systems can be challenging due to limited options for consistent and controlled stimulation. One method for mechanical stimulation of hollow organs, including the colon and bladder, is controlled distensions mediated by compressed air. For example, distension of the bladder can be used as an assay for bladder nociception. Bladder distension causes a corresponding increase in abdominal electromyography, which increases with distension pressure and is attenuated with analgesics. However, the hardware used to control these distensions are primarily all one-off custom builds, without clear directions on how to build your own. This has made it difficult for these methods to be fully utilized and replicated as not everyone has the access, knowledge, and resources required to build this controller. Here we show an open-source Arduino-based system for controlling a solenoid valve to deliver timed pressure distensions in the experimental model. This device can be controlled by one of two methods through direct TTL pulses from the experimenter's data acquisition software (ex. CED Spike2) or by a graphical user interface, where the user can set the time before, during, and after distension as well as the number of cycles. This system's low cost and relative ease to build will allow more groups to utilize timed pressure distensions in their experiments.

The role of bile acids in functional GI disorders

BACKGROUND

Bile acids are increasingly implicated in the pathogenesis of functional GI disorders. New mechanisms have recently been described in the irritable bowel syndrome, chronic diarrhea and chronic idiopathic constipation. Identification of bile acid signaling through farnesoid X receptor (FXR), transmembrane G-coupled receptor 5 (TGR5) and fibroblast growth factor 19 (FGF19) has led to the development of new, directly acting therapeutic agents. Despite these advances primary bile acid diarrhea remains under-recognized partly because of the lack of a widely available diagnostic test.

PURPOSE

In this review we will summarize the effects of bile acids on bowel function throughout the gastrointestinal tract and their roles in the pathogenesis of functional diseases. We will review established diagnostic tests and therapies for functional heartburn, dyspepsia and bile acid diarrhea. There will be a particular emphasis on recent trial data for emerging therapies such as Elobixibat and Obeticholic acid and novel diagnostic tests for bile acid diarrhea such as 7α-Hydroxy-4-cholesten-3-one (C4) and FGF19. Finally we will discuss future directions for research in this rapidly evolving field, such as bacterial bile acid modification and identification of genetic anomalies associated with functional disorders.

Pain without nociception?

We describe a young woman with complete cervical spinal cord transsection, who developed significant abdominal pain, triggered by gastric distension and deep abdominal palpation. On the basis of the nature of her spinal cord injury, her brain-gut axis was limited to vagal pathways. Studies in mammalian models of human visceral sensation consistently showed that the subdiaphragmatic vagus contains a homogeneous population of afferents that are activated by low-intensity stimuli, which are generally believed to be important in regulating autonomic function and perhaps contributing to visceral sensory experiences triggered by such low-intensity stimuli (e.g. fullness, nausea), but not pain, although many fibers encode stimuli well into the noxious range. In contrast, spinal afferent pathways include fibers with high-activation thresholds that are thought to represent specialized nociceptors. This illustrative case argues against an exclusive role of specialized nociceptive pathways in visceral pain, but supports a concept of intensity coding with the composite of vagal and spinal input contributing to conscious perception and pain.

Neurogenic inflammation in the upper digestive tract of the mule duck: effect of a chemical algogen and force-feeding

1.The objectives were to quantify the presence of neurogenic inflammation in 4 regions of the upper digestive tract of anaesthetised ducks (post-pharynx, pseudo-crop, transition between the pseudo-crop and the proventriculus, and proventriculus) after application of HCl stimulation of up to 4 M in the pseudo-crop. 2.The second objective was to quantify the presence of neurogenic inflammation in the same digestive tract regions as mentioned above during 4 feeding periods of foie gras production (rearing, preparation to force-feeding, and second and last meals of the force-feeding period). 3. Extravasation increased above a HCl stimulation threshold of 2 M. Furthermore, more extravasation was observed in the proventriculus compared to the other regions (P < 0·001). 4.Highest extravasation responses were observed in the proventriculus and the pseudo-crop at the end of the preparation period, and in the proventriculus after the second forced meal, compared with the rearing period (P < 0·01), with a return to rearing level at the end of force-feeding. 5.Such a kinetic could be indicative of a relative mildness of the irritant components associated with this feeding practice.