New insight on the enteric cholinergic innervation of the pig colon by central and peripheral nervous systems: reduction by repeated loperamide administration.

Introduction: The central and peripheral nervous systems provide cholinergic innervation in the colon. The ability to assess their neuroanatomical distinctions is still a challenge. The pig is regarded as a relevant translational model due to the close similarity of its enteric nervous system (ENS) with that of human. Opioid-induced constipation is one of the most common side effects of opioid therapy. Methods: We developed an approach to differentiate the central and peripheral cholinergic innervation of the pig colon using double immunolabeling with a novel mouse anti-human peripheral type of choline acetyltransferase (hpChAT) antibody combined with a rabbit anti-common type of ChAT (cChAT) antibody, a reliable marker of cholinergic neurons in the central nervous system. We examined their spatial configurations in 3D images of the ENS generated from CLARITY-cleared colonic segments. The density was quantitated computationally using Imaris 9.7. We assessed changes in the distal colon induced by daily oral treatment for 4 weeks with the µ opioid receptor agonist, loperamide (0.4 or 3 mg/kg). Results: The double labeling showed strong cChAT immunoreactive (ir) fibers in the cervical vagus nerve and neuronal somata and fibers in the ventral horn of the sacral (S2) cord while hpChAT immunoreactivity was visualized only in the ENS but not in the vagus or sacral neural structures indicating the selectivity of these two antibodies. In the colonic myenteric plexus, dense hpChAT-ir neurons and fibers and varicose cChAT-ir fibers surrounding hpChAT-ir neurons were simultaneously visualized in 3D. The density of cChAT-ir varicose fibers in the outer submucosal plexus of both males and females were higher in the transverse and distal colon than in the proximal colon and in the myenteric plexus compared to the outer submucosal plexus and there was no cChAT innervation in the inner submucosal plexus. The density of hpChAT in the ENS showed no segmental or plexus differences in both sexes. Loperamide at the highest dose significantly decreased the density hpChAT-ir fibers + somata in the myenteric plexus of the distal colon. Discussion: These data showed the distinct density of central cholinergic innervation between myenteric and submucosal plexuses among colonic segments and the localization of cChAT-ir fibers around peripheral hpChAT neurons in 3D. The reduction of cholinergic myenteric innervation by chronic opiate treatment points to target altered prokinetic cholinergic pathway to counteract opiate constipation.

Involvement of acid sensing ion channel (ASIC)-3 in an acute urinary bladder-colon cross sensitization model in rodent.

Introduction: Irritable bowel syndrome and bladder pain syndrome are both characterized by pain in response to organ distension. Epidemiologic studies showed that these two syndromes are often overlapped. Such overlap may be due to sharing of common extrinsic innervations between the colorectum and the urinary bladder, where cross-sensitization of the urinary bladder and the colon would occur in response to mechanical distension of either organ. The aim of this project was to develop and characterize a rodent model of urinary bladder-colon sensitization and to assess the role of the acid sensing ion channel (ASIC)-3. Methods: Double retrograde labelling was performed to identify extrinsic primary afferent neurons innervating both the colon (Fluororuby) and urinary bladder (Fluorogold) in the L6-S1 dorsal root ganglia (DRG) in Sprague Dawley rats. The phenotype of the colon/urinary bladder co-innervating primary afferent neurons was assessed using immunohistochemistry directed against ASIC-3. Cross-organ sensitization was induced in Sprague Dawley rats by using an echography-guided intravesical administration of acetic acid (0.75%) under brief isoflurane anesthesia. Colonic sensitivity was assessed in conscious rats by measuring abdominal contraction during isobaric colorectal distension (CRD). Measurement of urinary bladder and colonic paracellular permeabilities and tissue myeloperoxidase assay were performed. The involvement of ASIC-3 was assessed by use of S1 intrathecal administration of the ASIC-3 blocker, APETx2 (2.2 µM). Results: Immunohistochemistry showed that 73.1% of extrinsic primary afferent neurons co-innervating the colon and the urinary bladder express ASIC-3. By contrast, extrinsic primary afferent neurons innervating the colon only or the urinary bladder only were positive for ASIC-3 in 39.3% and 42.6%, respectively. Echography-guided intravesical administration of acetic acid resulted in colonic hypersensitivity to colorectal distension. This effect started 1 h post-injection and lasted up to 24 h, and was not longer seen after 3 days after injection. No colonic hyperpermeability and no difference in urinary bladder and colon MPO activity was observed between control and acetic acid-treated rats. Colonic sensitization by intravesical acetic acid administration was prevented by S1 intrathecal administration of APETx2. Conclusion: We developed an acute pelvic cross-organ sensitization model in conscious rat. In this model, cross-organ sensitization is likely to involve S1-L6 extrinsic primary afferents co-innervating the colon and urinary bladder through an ASIC-3 pathway.

Bladder-colon chronic cross-sensitization involves neuro-glial pathways in male mice.

BACKGROUND: Irritable bowel syndrome and bladder pain syndrome often overlap and are both characterized by visceral hypersensitivity. Since pelvic organs share common sensory pathways, it is likely that those syndromes involve a cross-sensitization of the bladder and the colon. The precise pathophysiology remains poorly understood. AIM: To develop a model of chronic bladder-colon cross-sensitization and to investigate the mech-anisms involved. METHODS: Chronic cross-organ visceral sensitization was obtained in C57BL/6 mice using ultrasound-guided intravesical injections of acetic acid under brief isoflurane anesthesia. Colorectal sensitivity was assessed in conscious mice by measuring intracolonic pressure during isobaric colorectal distensions. Myeloperoxidase, used as a marker of colorectal inflammation, was measured in the colon, and colorectal permeability was measured using chambers. c-Fos protein expression, used as a marker of neuronal activation, was assessed in the spinal cord (L6-S1 level) using immunohistochemistry. Green fluorescent protein on the fractalkine receptor-positive mice were used to identify and count microglia cells in the L6-S1 dorsal horn of the spinal cord. The expression of NK1 receptors and MAPK-p38 were quantified in the spinal cord using western blot. RESULTS: Visceral hypersensitivity to colorectal distension was observed after the intravesical injection of acetic acid vs saline (P < 0.0001). This effect started 1 h post-injection and lasted up to 7 d post-injection. No increased permeability or inflammation was shown in the bladder or colon 7 d post-injection. Visceral hypersensitivity was associated with the increased expression of c-Fos protein in the spinal cord (P < 0.0001). In green fluorescent protein on the fractalkine receptor-positive mice, intravesical acetic acid injection resulted in an increased number of microglia cells in the L6-S1 dorsal horn of the spinal cord (P < 0.0001). NK1 receptor and MAPK-p38 levels were increased in the spinal cord up to 7 d after injection (P = 0.007 and 0.023 respectively). Colorectal sensitization was prevented by intrathecal or intracerebroventricular injections of minocycline, a microglia inhibitor, by intracerebroventricular injection of CP-99994 dihydrochloride, a NK1 antagonist, and by intracerebroventricular injection of SB203580, a MAPK-p38 inhibitor. CONCLUSION: We describe a new model of cross-organ visceral sensitization between the bladder and the colon in mice. Intravesical injections of acetic acid induced a long-lasting colorectal hypersensitivity to distension, mediated by neuroglial interactions, MAPK-p38 phosphorylation and the NK1 receptor.

Ghrelin inhibits autonomic response to gastric distension in rats by acting on vagal pathway.

Ghrelin is the only orexigenic peptide currently known and a potent prokinetic by promoting gastric motility but novel insights suggest that its role extends beyond satiety regulation. Whereas ghrelin was shown to provide somatic and colonic antinociception, its impact on gastric sensitivity is unknown even though stomach is a major ghrelin secreting tissue. Autonomic response to gastric mechanosensitivity was estimated by measuring blood pressure variation as a surrogate marker in response to gastric distension (GD) before and after ghrelin (or vehicle) administration. Involvement of spinal and vagal pathways in the ghrelin effect was studied by performing celiac ganglionectomy and subdiaphragmatic vagotomy respectively and by evaluating the expression of phosphorylated extracellular-regulated kinase 1/2 (p-ERK1/2) in dorsal root and nodose ganglia. Finally the phenotype of Ghrelin receptor expressing neurons within the nodose ganglia was determined by in situ hybridization and immunofluorescence. Ghrelin reduced blood pressure variation in response to GD except in vagotomized rats. Phosphorylated-ERK1/2 levels indicated that ghrelin reduced neuronal activation induced by GD in nodose ganglion. The effect of ghrelin on gastric mechanosensitivity was abolished by pre-treatment with antagonist [D-Lys3]-GHRP-6 (0.3 mg/kg i.v.). Immunofluorescence staining highlights the colocalization of Ghrelin receptor with ASIC3 and TRPV1 within gastric neurons of nodose ganglion. Ghrelin administration reduced autonomic response to gastric distension. This effect likely involved the Ghrelin receptor and vagal pathways.

Stress-induced intestinal barrier dysfunction is exacerbated during diet-induced obesity.

Obesity and irritable bowel syndrome (IBS) are two major public health issues. Interestingly previous data report a marked increase of IBS prevalence in morbid obese subjects compared with non-obese subjects but underlying mechanisms remain unknown. Obesity and IBS share common intestinal pathophysiological mechanisms such as gut dysbiosis, intestinal hyperpermeability and low-grade inflammatory response. We thus aimed to evaluate the link between obesity and IBS using different animal models. Male C57Bl/6 mice received high fat diet (HFD) for 12 weeks and were then submitted to water avoidance stress (WAS). In response to WAS, HFD mice exhibited higher intestinal permeability and plasma corticosterone concentration than non-obese mice. We were not able to reproduce a similar response both in ob/ob mice and in leptin-treated non-obese mice. In addition, metformin, a hypoglycemic agent, limited fasting glycaemia both in unstressed and WAS diet-induced obese mice but only partially restored colonic permeability in unstressed HFD mice. Metformin failed to improve intestinal permeability in WAS HFD mice. Finally, cecal microbiota transplantation from HFD mice in antibiotics-treated recipient mice did not reproduce the effects observed in stressed HFD mice. In conclusion, stress induced a more marked intestinal barrier dysfunction in diet-induced obese mice compared with non-obese mice that seems to be independent of leptin, glycaemia and gut microbiota. These data should be further confirmed and the role of the dietary composition should be studied.

Development of a Remote-Controlled Implantable Rat Sacral Nerve Stimulation System.

OBJECTIVES: Sacral nerve stimulation (SNS) is a surgical treatment of urinary and fecal incontinence. Despite its clinical efficacy, the mechanisms of action of SNS are still poorly known. This may be related to the use of acute stimulation models. Up to date, no rodent model of chronic SNS implants has been developed. Therefore, the aim of this study was to create a fully implantable and remotely controllable stimulating device to establish an animal model of chronic SNS. MATERIALS AND METHODS: The stimulating device consisted of an implantable pulse generator linked to a platinum electrode. The communication with the device was made through an inductive link which allowed to adjust the stimulation parameters; that is, to turn the device on and off or check the battery status remotely. Rats underwent two surgical procedures. In the first procedure, we achieved chronic sacral stimulation but the implanted electrode was not fixated. In the second procedure, the electrode was fixated in the sacral foramen using dental resin. In both cases, the correct positioning of the electrode was evaluated by computed tomography (CT) imaging and the presence of tail tremor in response to high intensity stimulation. We only tested the function of implanted electrode with fixation using micturition frequency assessment following bipolar or unipolar SNS for three days after recovery. RESULTS: CT imaging showed that implantation of the electrode required fixation as we found that the second surgical procedure yielded a more precise placement of the implanted electrode. The correct placement of implanted electrode observed with imaging was always correlated with a successful tail tremor response in rats, therefore we pursued our next experiments with the second surgical procedure and only assessed the tail tremor response. We found that both bipolar and unipolar SNS reduced micturition frequency. CONCLUSION: This stimulating device provides an efficient method to perform chronic SNS studies in rats.

Preferential hyperacuity perimeter in best vitelliform macular dystrophy.

PURPOSE: To determine the visual field patterns obtained by the preferential hyperacuity perimetry (PHP) in patients with Best vitelliform macular dystrophy with mutations in the BEST1 gene. METHODS: Consecutive patients with Best vitelliform macular dystrophy underwent a complete ophthalmologic examination, including functional assessment by best-corrected visual acuity and Foresee PHP and morphologic assessment by fundus biomicroscopy, fundus autofluorescence, and spectral-domain optical coherence tomography. The functional "PHP visual field defect index" (which is the max peak value of the metamorphopsia [maximal distortion value at the visual field] + the max peak value of the scotoma [maximal scotoma value at the visual field]) and best-corrected visual acuity were analyzed about the disease stage. RESULTS: Thirty eyes of 15 consecutive patients (8 men and 7 women; mean age 39 ± 24 years) were included for analysis. Based on fundus biomicroscopy, fundus autofluorescence, and spectral-domain optical coherence tomography, the macular lesions could be counted as follows: previtelliform lesions in 5 eyes of 3 patients (Stage 1), vitelliform lesions in 2 eyes of 2 patients (Stage 2), pseudohypopyon lesions in 6 eyes of 5 patients (Stage 3), vitelliruptive lesions in 4 eyes of 3 patients (Stage 4), atrophic lesions in 7 eyes of 5 patients (Stage 5), and fibrotic lesions in 6 eyes of 4 patients (Stage 6). Best-corrected visual acuity and PHP visual field defect index were averaged for each stage. Best-corrected visual acuity showed a good correlation (P = 0.01) with the morphologic severity (stage) of the disease (Pearson correlation = -0.88). Similarly, the PHP visual field defect index showed a good correlation (P = 0.03) with the morphologic severity (stage) of the disease (Pearson correlation = 0.78). Finally, best-corrected visual acuity showed a good correlation (P = 0.02) with the functional PHP visual field defect index (Pearson correlation = -0.83) about the morphologic stage of the disease. CONCLUSION: Preferential hyperacuity perimetry could be considered an adjunctive useful tool in the evaluation of functional impairment and disease progression in patients with Best vitelliform macular dystrophy.

Analysis of retinal flecks in fundus flavimaculatus using high-definition spectral-domain optical coherence tomography.

PURPOSE: To assess morphologic changes associated with retinal flecks in fundus flavimaculatus using spectral-domain optical coherence tomography (SD-OCT). DESIGN: Observational case series. METHODS: Simultaneous recordings of SD-OCT and confocal scanning laser ophthalmoscope (cSLO) fundus autofluorescence images were obtained in fundus flavimaculatus patients. Morphologic aspects of the retinal flecks were analyzed and classified. RESULTS: Thirty-one eyes of 17 consecutive patients (8 male, 9 female; mean age 47.9 +/- 17.1 years) were included for analysis. SD-OCT revealed 5 distinct types of lesions. Group A lesions were limited to the outer segment (OS) of the photoreceptors, the retinal pigment epithelium (RPE) interdigitations, and the RPE/Bruch membrane complex. Group B showed a protrusion of the hyper-reflective material through the interface of inner segment (IS)/OS of the photoreceptors up to the external limiting membrane. A further protrusion of the hyper-reflective material into the outer nuclear layer was seen in group C lesions. Group D lesions were characterized by an accumulation of the hyper-reflective material limited to the outer nuclear layer. Type E lesions can be described as drusen-like retinal pigment detachments. No significant correlation between the different types of flecks and visual acuity was observed (P > .05). CONCLUSIONS: SD-OCT allows one to distinguish at least 5 different types of lesions associated with retinal flecks in fundus flavimaculatus. The ability to characterize the different types of flecks and to analyze the photoreceptor layers surrounding these lesions suggests that SD-OCT might have a potential clinical role in the evaluation and follow-up of the structural changes in fundus flavimaculatus.

Angiographic analysis of retinal-choroidal anastomosis by confocal scanning laser ophthalmoscopy technology and corresponding (eye-tracked) spectral-domain optical coherence tomography.

PURPOSE: The purpose of this study was to analyze the angiographic (confocal scanning laser ophthalmoscopy technology) and corresponding (eye-tracked) spectral-domain optical coherence tomography (SD-OCT) features and to propose a classification for the progressive phases establishing retinal-choroidal anastomosis (RCA). METHODS: We reviewed all consecutive eyes with RCA that underwent Heidelberg Retina Angiograph angiography and tracked Spectralis SD-OCT at the University Eye Clinic of Creteil between September 2007 and March 2009. RESULTS: Twenty-six eyes of 23 patients (8 men and 15 women, aged 70-88 years) showing RCA naïve to any treatment were included for analysis. In 6 of 7 eyes showing a discrete focal hyperfluorescence (focal staining), the corresponding (eye-tracked) SD-OCT scan showed a focal retinal pigment epithelium (RPE) erosion ("erosion sign") over a small, localized RPE elevation (which appeared filled with a hyperreflective material); in 7 of 8 eyes showing a typical "hot spot" in the late angiographic frames (focal leakage) and absence of a serosanguineous pigment epithelium detachment, the corresponding (eye-tracked) SD-OCT scan showed a focal RPE break leaving 2 free RPE flaps ("flap sign") at the level of a small, localized RPE elevation. In 10 of 11 eyes showing a typical hot spot in the late angiographic frames and presence of a serosanguineous pigment epithelium detachment, the corresponding (eye-tracked) SD-OCT scan showed, at the level of a large serosanguineous RPE detachment, a focal funnel-shaped RPE joining (kissing) an inverted focal funnel-shaped inner neuroepithelium ("kissing sign"). CONCLUSION: An early neovascularization (a discrete focal hyperfluorescence) arising from the choroid initially simply erodes the basement membrane/RPE (erosion sign; Phase 1) and later breaks the basement membrane/RPE (flap sign), infiltrating first into the outer retina forming an early RCA (Phase 2, a typical hot spot without a serosanguineous pigment epithelium detachment) and later into the inner retina (kissing sign) forming an established RCA (Phase 3, a typical hot spot with a serosanguineous pigment epithelium detachment).