A new intelligent distension system for hollow organs

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.

Heightened central affective response to visceral sensations of pain and discomfort in IBS

BACKGROUND Typically, conventional functional imaging methods involve repeated exposures to sensory stimulation. In rectal distension (RD) studies that involve multiple distensions, however, it is difficult to disambiguate the central response to RD from pathological alterations in peripheral neural responses associated with relaxation and accommodation of the rectum. METHODS This study addressed potential confounders found in previous imaging studies by collecting functional magnetic resonance imaging studies (fMRI) data during a single slow ramp-tonic distension paradigm and analysing fMRI signal changes using independent component analysis. KEY RESULTS Compared with controls, IBS participants showed increased activation of the anterior cingulate cortices, insula and ventral medial prefrontal regions suggesting heightened affective responses to painful visceral stimuli. In addition, the failure by IBS patients to down-regulate activity within ventral medial prefrontal and the posterior cingulate/precuneus regions was suggestive of reduced sensitivity to somatic changes and delayed shifts away from rest in ;default network' activity patterns. Controls showed heightened activation of the thalamus, striatal regions and dorsolateral prefrontal cortex suggesting greater arousal and salience-driven sustained attention reactions and greater modulation of affective responses to discomfort and pain. CONCLUSION&INFERENCES This work points to alterations in the central response to visceral pain and discomfort in IBS, highlighting diminished modulation and heightened internalization of affective reactions.

Vagal dysfunction in irritable bowel syndrome assessed by rectal distension and baroreceptor sensitivity

Autonomic nervous system dysfunction has been implicated in the pathophysiology of irritable bowel syndrome (IBS). This study characterized the autonomic response to rectal distension in IBS using baroreceptor sensitivity (BRS), a measure of autonomic function. Rectal bag pressure, discomfort, pain, ECG, blood pressure and BRS were continuously measured before, during and after rectal distension in 98 healthy volunteers (34 +/- 12 years old, 52 females) and 39 IBS patients (39 +/- 11 years old, 35 females). In comparison with the healthy volunteers, IBS patients experienced significantly more discomfort (69 +/- 2.2% vs 56 +/- 3.6%; P < 0.05), but not pain (9 +/- 1.4% vs 6 +/- 2.4%; ns) with rectal distension despite similar distension pressures (51 +/- 1.4 vs 54 +/- 2.4 mmHg; ns) and volumes (394 +/- 10.9 vs 398 +/- 21.5 mL; ns). With rectal distension, heart rate increased in both healthy volunteers (66 +/- 1 to 71 +/- 1 bpm; P < 0.05) and IBS patients (66 +/- 2 to 74 +/- 3 bpm; P < 0.05). Systolic blood pressure also increased in both healthy volunteers (121 +/- 2 to 143 +/- 2 mmHg; P < 0.05) and patients (126 +/- 3 to 153 +/- 4 mmHg (P < 0.05) as did diastolic blood pressure, 66 +/- 2 to 80 +/- 2 mmHg (P < 0.05), compared with 68 +/- 3 to 84 +/- 3 mmHg (P < 0.05) in IBS patients. The systolic blood pressure increase observed in IBS patients was greater than that seen in healthy volunteers and remained elevated in the post distension period (139 +/- 3 mmHg vs 129 +/- 2 mmHg; P < 0.05). IBS patients had lower BRS (7.85 +/- 0.4 ms mmHg(-1)) compared with healthy volunteers (9.4 +/- 0.3; P < 0.05) at rest and throughout rectal distension. Greater systolic blood pressure response to rectal distension and associated diminished BRS suggests a compromise of the autonomic nervous system in IBS patients.