Prolonged pudendal nerve terminal motor latency is associated with decreased resting and squeeze pressures in the intact anal sphincter.

AIM: To determine the contribution of the pudendal nerve to the anal continence mechanism by determining the correlation between pudendal nerve terminal motor latency (PNTML) and resting and squeeze anal canal pressures. METHOD: In all, 1051 patients were investigated with anorectal physiology studies between January 1998 and July 2010. Of these, 213 patients had intact anal sphincters on endoanal ultrasound and had undergone PNTML testing and anal manometry with measurement of resting and squeeze pressures. The relationship between PNTML and mean resting and squeeze pressures was compared in these patients with an intact anal sphincter. Values were compared using a two-sample t test with equal variances. A P value of < 0.05 was considered significant. RESULTS: Of these patients 40.8% had normal PNTML bilaterally, 9.9% had slow PNTML bilaterally and 21.6% had a unilateral slow PNTML. Mean resting pressure was significantly reduced in patients with unilateral slow and bilateral slow PNTML compared with normal. The magnitude of the reduction was 28% and 19% respectively. Mean squeeze pressure was significantly reduced in patients with unilateral slow and bilateral slow PNTML compared with normal. The magnitude of the reduction was 18% and 23% respectively. CONCLUSION: In patients with an intact anal sphincter, either unilaterally or bilaterally prolonged PNTMLs are associated with significantly decreased resting and squeeze pressures. Our results suggest that both internal and external sphincter function is impaired with pudendal nerve injury. The inhibition of internal sphincter function may be due to damage of autonomic, principally sympathetic fibres carried in the pudendal nerve.

Galanin receptor 3--a potential target for acute pancreatitis therapy.

BACKGROUND: Galanin participates in the pathogenesis of acute pancreatitis (AP). The galanin receptor (GALR) sub-types involved, however, are unclear. We aimed to determine GALRs messenger RNA (mRNA) expression in mouse pancreas, describe their localization, and ascertain if GALR2 and GALR3 are involved in AP. METHODS: Galanin receptor expression in murine whole pancreas, acinar, and islet cells was quantified by polymerase chain reaction amplification of reverse-transcribed RNA for mRNA, Western blot analysis for protein and in situ hybridization for GALR localization. Isolated acinar cells were used to determine galanin's effect on amylase secretion. Acute pancreatitis was induced in mice by caerulein injections. Mice, with and without AP, were treated with the highly selective GALR2 antagonist M871, or the specific GALR3 antagonist SNAP-37889. Indices of AP were measured at 12 h. KEY RESULTS: Murine pancreas expresses mRNA for GALRs. In islets the expression of all GALR are comparable, whereas in acinar cells GALR3 is predominantly expressed. Western blot analysis confirmed that the GALR proteins are expressed by acinar cells. In situ hybridization analysis confirmed that GALR3 mRNA is present in islet and acinar cells, while mRNA for GALR1 and 2 is confined to islets. Galanin did not influence basal and caerulein-stimulated amylase release from acinar cells. M871 treatment reduced some, whereas SNAP-37889 treatment reduced all indices of AP (by 40-80%). CONCLUSIONS & INFERENCES: Galanin receptor mRNA and protein are expressed in mouse pancreas, with GALR3 mRNA predominating. GALR3 antagonism reduced the severity of AP whereas GALR2 antagonism was less effective. GALR3 is a potential target for treatment of AP.

Galanin receptor antagonist m35 but not m40 or c7 ameliorates cerulein-induced acute pancreatitis in mice.

BACKGROUND/AIMS: We compared the galanin antagonists C7, M35, M40 and galantide, for their ability to ameliorate acute pancreatitis (AP). METHODS: Galanin antagonists were co-administered with 7 hourly cerulein injections used to induce AP. Plasma amylase and lipase activities were measured as indices of AP, and pancreata were harvested at 12 h for histological examination and estimation of myeloperoxidase (MPO) activity. RESULTS: Treatment with galantide, M35 and C7 ameliorated the AP-induced plasma hyperenzymemia by 40-75%. Administration of M40 did not significantly alter plasma hyperenzymemia. Galantide, M35 and M40 significantly reduced the pancreatic MPO activity by 65-80%, whereas C7 increased MPO activity. Galantide and M35 but not C7 or M40 treatment significantly reduced the AP-induced necrosis score by 30-50% compared to the AP alone group. C7 alone increased plasma lipase activity and the pancreatic necrosis score compared with saline treatment alone, whereas the other antagonists were without effect. CONCLUSION: Galantide and M35 ameliorated the severity of AP, but M40 and C7 had mixed effects. Complex galanin pathways may be involved in cerulein-induced AP. M35 and galantide are potential therapeutic peptides for the treatment of AP and further evaluation should be considered. and IAP.

A novel preparation to study rat pancreatic spinal and vagal mechanosensitive afferents in vitro.

The management of pancreatic pain is a significant clinical problem so understanding of how sensory signals are generated in pancreatic tissue is fundamental. We aimed to characterize mechanosensitive and chemosensitive properties of pancreatic spinal and vagal afferents in vitro. Spinal and vagal afferent preparations from Sprague-Dawley rats were established incorporating the left splanchnic nerve or vagus nerves respectively. The common bile duct was cannulated for distension of the pancreatic duct with fluid. Nerve discharge evoked by blunt probing, duct distension or electrical stimulation was obtained from teased nerve bundles using standard extra-cellular recording. Discharge from 197 spinal afferent bundles was recorded, of which 57% displayed spontaneous activity. Blunt probing revealed 61 mechanosensitive receptive fields which were associated primarily with arteries/blood vessels (33/61) and the parenchyma (22/61). All mechanosensitive responses were slowly adapting, with 33% continuing to discharge after termination of the stimulus and 60% displaying a response threshold <10 g. Application of chemical mediators (bradykinin, histamine, 5-hydroxytryptamine, cholecystokinin octapeptide) evoked a response from 31/57 units, with 33% excitatory and 23% inhibitory. Spontaneous discharge was recorded from 72% of 135 vagal bundles. Mechanosensitive receptive fields were not identified in the pancreas but were evident in adjacent organs. No spinal or vagal afferent response to duct distension was obtained. In conclusion, pancreatic mechanosensitive spinal afferents are common, in contrast to pancreatic mechanosensitive vagal afferents indicating that pancreatic sensory innervation is predominantly spinal. Chemosensitive spinal afferent nerve endings are present in the pancreas and respond to a variety of inflammatory and physiological mediators.

Sphincter of Oddi function in the Australian brush-tailed possum is inhibited by intragastric ethanol.

The role of sphincter of Oddi (SO) function in alcoholic acute pancreatitis (AP) is unclear. We aimed to compare the effect of i.v. and intragastric (IG) ethanol on SO function (i.e. trans-sphincteric flow; TSF) and investigate possible neural mechanisms. The involvement of gastric mucosal damage was also investigated by pretreatment with pantoprazole. In anaesthetized Australian possums, blood pressure (BP), TSF and blood ethanol concentrations were measured after i.v. or IG ethanol. Possums were subjected to acute vagotomy, atropine, L-nitro arginine methyl ester (L-NAME) or pantoprazole pretreatment prior to IG ethanol. BP was not significantly altered by ethanol. Ethanol decreased TSF in a dose and route-dependent manner. The lowest dose of IG ethanol reduced TSF but this response was not duplicated by i.v. ethanol producing the same blood ethanol concentrations. Acute vagotomy, atropine or L-NAME pretreatment blocked the ethanol-induced decrease in TSF and simultaneously suppressed the blood ethanol concentration. Pantoprazole pretreatment reduced the TSF response and blood ethanol concentrations implicating mechanisms induced by gastric mucosal damage. We conclude that ethanol (and/or its metabolites) reduces TSF via humoral and neural mechanisms involving vagal pathways, muscarinic receptors and nitric oxide. Reduced TSF could contribute to the onset of AP.

Pancreatobiliary afferent recordings in the anaesthetised Australian possum.

The sensory innervation to the pancreatobiliary system is poorly characterized. Afferent signals from the gastrointestinal tract and biliary tree are transmitted to the central nervous system via the vagus and spinal nerves. We aimed to record afferent discharge in order to characterize the vagal and splanchnic afferent signals from the possum upper gastrointestinal tract, biliary tree and pancreas. In 21 anaesthetised possums nerve fibres were teased from the vagus or splanchnic nerve for multi-unit recording. Mechanical stimuli consisted of balloon distension of the gallbladder and duodenum (2-7 ml) and fluid distension (0-20 mm Hg) of the bile or pancreatic ducts. Approximately 60% of fibres from all nerves displayed spontaneous discharge. Spinal afferent responses to mechanical stimuli were infrequent (n=13). Increased discharge occurred in response to duodenal (12/99 fibres) or gallbladder (7/96 fibres) distension, but not to bile duct (0/73 fibres) or pancreatic duct (0/51 fibres) distension. Vagal afferent responses to distension of the duodenum or stomach (5-30 ml) were more common (n=8). Increased discharge was recorded in response to duodenal (49/134 fibres), or gastric (22/70 fibres) distension. Responses to gallbladder distension were less frequent (6/99 fibres) and as with the spinal afferent no response to bile duct (0/66) or pancreatic duct (0/70) distension were recorded. We conclude that mechanosensitive afferents in the pancreatobiliary system are relatively rare, particularly within the ducts, and/or that they are adapted to monitor stimuli other than luminal distension.

Electrical activation of common bile duct nerves modulates sphincter of Oddi motility in the Australian possum.

BACKGROUND: Sphincter of Oddi (SO) motility is regulated by extrinsic and intrinsic nerves. The existence of neural circuits between the SO and the proximal extrahepatic biliary tree has been reported, but they are poorly understood. Using electrical field stimulation (EFS), we determined if a neural circuit exists between the common bile duct (CBD) and the SO in anaesthetized Australian brush-tailed possums. METHODS: The gallbladder, cystic duct or CBD were subjected to EFS with a stimulating electrode. Spontaneous SO phasic waves were measured by manometry. RESULTS: EFS at sites on the distal CBD (12-20 mm proximal to the SO), but less commonly at more proximal CBD, evoked a variety of responses consisting of an excitatory and/or inhibitory phase. Bi-phasic responses consisting of an excitation followed by inhibition were the most common. Tri-phasic responses were also observed as well as excitation or inhibition only. These evoked responses were blocked by topical application of local anaesthetic to the distal CBD or transection of the CBD. EFS at sites on the gallbladder body, neck or cystic duct did not consistently evoke an SO response. Pretreatment with atropine or guanethidine reduced the magnitude of the evoked response by about 50% (p<0.05), pretreatment with hexamethonium had no consistent effect and pretreatment with a nitric oxide synthase inhibitor increased the response. DISCUSSION: A neural circuit(s) between the SO and the distal CBD modulates SO motility. Damage to this area of the CBD during bile duct exploration surgery could adversely affect SO motility.

Scorpion venom stimulates biliary/duodenal motility and pancreatic exocrine secretion.

Scorpion envenomation causes severe upper abdominal pain associated with nausea and vomiting. Although scorpion venom (SV) stimulates pancreatic and gastric secretion in animal models, its effects on duodenal and biliary motility have not been reported. The aim of this study was to determine the effects of SV on sphincter of Oddi (SO), duodenal and gall bladder motility and pancreatic amylase output. Anaesthetized Australian possums (n = 21) were infused with SV via intravenous or closed intra-arterial routes. Blood pressure, SO, duodenal and gall bladder motility were continuously monitored for 4 h. Trans-sphincteric flow (TSF), an indicator of bile duct resistance, was measured concurrently. The amylase output in pancreatic juice was also measured. SV infusion resulted in profound transient increase in blood pressure, SO motility and a significant decrease in TSF. No significant differences were noted in SO basal pressure changes. A transient increase in gall bladder tone, duodenal contraction amplitude and frequency, and amylase output were noted. Following the peak in blood pressure, amylase output, SO, gall bladder and duodenal motility were depressed. SV induces a rapid but transient increase in biliary and duodenal motility that is associated with stimulation of pancreatic amylase output. These changes may contribute to gastrointestinal symptoms associated with early phases of envenomation.

Anal sphincter tears in patients with rectal prolapse and faecal incontinence.

OBJECTIVE: Faecal incontinence often persists after surgery for rectal prolapse. Multiple mechanisms have been proposed as responsible, however, anal sphincter integrity has only been studied in a handful of cases. This study assesses the incidence of ultrasound detected anal sphincter tears in patients with rectal prolapse and faecal incontinence. METHODS: Retrospective search of medical records at Flinders Medical Centre over a 7-year period to identify patients with full thickness rectal prolapse and faecal incontinence who had undergone endosonographical imaging of the anal sphincter complex. Anal manometry and pudendal nerve terminal motor latency studies were also included. RESULTS: Twenty-one patients were identified (1 male, 20 female) of median age 67.5 years. Fifteen (71%) subjects had an abnormality in the anal sphincter complex on endoanal ultrasound. Of these, the defects in 4 (19%) patients were isolated to the internal sphincter, 3 (14%) to the external sphincter and in the remaining 8 (38%) subjects, defects were found in both internal and external sphincters. The degree of sphincteric defect was variable but at least 6 (29%) of the study group had full-length external sphincter tears. In the 19 patients studied, anal manometry revealed reduced basal and squeeze pressures in the majority. Delayed pudendal nerve terminal motor latency was evident in 9 of 18 patients studied. CONCLUSION: Anal sphincter tears are common in patients presenting with rectal prolapse and faecal incontinence. The faecal incontinence associated with prolapse appears to be multifactorial in aetiology. Anal sphincter defects are likely to contribute to persistent faecal incontinence or recurrence following rectal prolapse. Endoanal ultrasound derived knowledge of anal sphincter injury may guide surgical management in problematic cases.

Characterization of the intrinsic and extrinsic innervation of the gall bladder epithelium in the Australian Brush-tailed possum (Trichosurus vulpecula).

Intrinsic neurones of the gall bladder modulate its function. Nitric oxide synthase (NOS) and vasoactive intestinal polypeptide (VIP) are present in gall bladder neurones and nitric oxide and VIP modulate its epithelial functions. As an extensive extrinsic innervation of the gall bladder is also present, the source of the epithelial innervation is unclear. In this study the source of the gall bladder epithelial innervation is defined. Immunoreactivity for VIP, NOS, substance P (SP), calcitonin gene related peptide (CGRP) and tyrosine hydroxylase (TH) in organotypic cultured and freshly fixed gall bladder were compared. Retrograde tracing in vitro from the epithelium was used to identify putative intrinsic secretomotor neurones, which were then characterized by immunohistochemistry. Abundant spinal afferent and sympathetic innervation of the gall bladder epithelium was demonstrated by CGRP/SP and TH immunohistochemistry, respectively. The intrinsic secretomotor innervation of the epithelium is derived exclusively from neurones of the subepithelial plexus. A majority of these neurones were immunoreactive for NOS. Some of the NOS-immunoreactive neurones of the subepithelial plexus also contained VIP and/or SP. Gall bladder subepithelial plexus neurones, containing NOS and/or VIP/SP, innervate the epithelium, as do extrinsic neurones.

Endothelin-1 stimulates sphincter of Oddi motility and decreases trans-sphincteric flow: a possible mechanism contributes to cholestasis in disease states.

Endothelin-1 (ET-1) is a potent stimulator of gallbladder contractility. Its role in modulation of sphincter of Oddi (SO) motility and trans-sphincteric flow (TSF) has not been evaluated. To characterize the effects of ET-1 on SO motility and TSF, 10 anaesthetized Australian possums (in vivo, n = 6) were given graded doses of ET-1 (5-200 pmol kg-1) via closed intra-arterial injection. Blood pressure, TSF and SO motility (basal pressure, phasic amplitude, contraction frequency) were analysed. For in vitro studies, eight SO rings were subjected to 10-12-10-7 mol L-1 cumulative concentrations of ET-1 in organ bath and SO motility was measured. Data are expressed as mean +/- SEM. Statistical analysis used anova. ET-1 induced a dose-related increase in blood pressure with a maximal increase of 37.5 +/- 2.5 mmHg at 200 pmol kg-1, (P < 0.001). ET-1 also increases SO basal pressure (P < 0.001) and contraction frequency (P < 0.0001). However, the contraction amplitude was not significantly affected. ET-1 decreased TSF in a dose-related manner (P < 0.001) with cessation of TSF at the highest dose (P < 0.001). In vitro studies showed a significant increase in mean SO motility index, and frequency of contractions at higher ET-1 concentrations (10-9-10-7 mol L-1). ET-1 is a potent stimulator of SO motility resulting in a reduction in TSF.

Effects of acute pancreatic duct obstruction on pancreatic perfusion: implication of acute pancreatic duct decompression.

BACKGROUND: Acute pancreatitis can result in pancreatic ischaemia and necrosis. Pancreatic duct (PD) obstruction may be the first step causing ischaemia in acute pancreatitis. Nitric oxide donors can attenuate acute pancreatitis through improvement in compromised pancreatic perfusion (PP). In this study, we determined if (1) PD obstruction altered PP and (2) PD decompression or L-arginine administration reversed this change. METHODS: Fifteen Australian possums were randomly assigned to two groups: Animals in group A (n = 6) were subjected to 30 min of PD obstruction and 60 min of PD decompression. Animals in group B (n = 9) were subjected to 120 min PD ligation and 60 min PD decompression. A subset group B (n = 6) were subjected to intravenous L-arginine (100 microg/kg) at the end of 120 min of ligation and at the end of PD decompression. The PP (Laser Doppler fluxmetry), PD pressure and blood pressure were continuously monitored. RESULTS: PD pressure increased from 2.9 +/- 2.5 to 18.1 +/- 4.9 mmHg following PD ligation. PP was reduced to 67.1% +/- 4.5% (P<0.01) and 46.2% +/- 7.5% (P<0.001) of baseline following 30 and 120 min of PD ligation, respectively. Following 60 min of PD decompression, PP was restored to 89.1% +/- 13.4% (P<0.02) of the baseline in the 30-min group. However, following 120 min PD ligation, PP remained depressed. L-arginine administration after 120 min of PD ligation transiently increased PP from 46.2% +/- 7.5% to 81.1% +/- 8.6% (P<0.03) of baseline. This effect was reproduced if L-arginine was administered at the end of decompression (P<0.05). CONCLUSION: In patients with acute pancreatitis due to obstructive causes, early decompression of the PD may prevent early pancreatic ischaemia.

Secretin induces variable inhibition of motility in different parts of the Australian possum sphincter of Oddi.

The sphincter of Oddi (SO) may not function as a single structure. We aimed to determine the response of the proximal and distal segments of the bile duct (BD-SO) and pancreatic duct (PD-SO) components of the SO to secretin, with and without neural blockade with tetrodotoxin (TTX). In anaesthetized Australian possums, separate manometry catheters were placed in the proximal and distal BD-SO or PD-SO segments to record motility. Secretin, 50-1000 ng kg(-1), was administered, followed by TTX, and re-administration of secretin, 500 and 1000 ng kg(-1). Changes in the motility index (MI, frequency x mean amplitude) were determined. Statistical analysis utilized repeated-measures ANOVA. Secretin produced a dose-dependent decrease in MI from the proximal and distal BD-SO and PD-SO (all P < 0.001). The maximum inhibition, at 1000 ng kg(-1), was 21 +/- 4%, 33 +/- 6% and 42 +/- 5% of control (mean +/- SEM), for proximal and distal BD-SO, and distal PD-SO, respectively. The proximal PD-SO MI, however, was inhibited to 62 +/- 6% of control, at 1000 ng kg(-1). TTX enhanced the secretin-induced response to the same level at the four sites (P < 0.02). We conclude that secretin inhibits the motility of the possum SO in a nonuniform manner and is modulated by neural activity.

Inhibitory motor innervation of the gall bladder musculature by intrinsic neurones containing nitric oxide in the Australian brush-tailed possum (Trichosurus vulpecula).

BACKGROUND: Gall bladder functions are modulated by neurones intrinsic to the organ. Data are available on the neurochemical composition of intrinsic and extrinsic nerves innervating the gall bladder but are lacking on specific functional classes of gall bladder neurones. AIMS: To characterise the intrinsic motor neurones of the gall bladder and identify their roles using pharmacological techniques. METHODS: Retrograde tracing from the possum gall bladder muscle in vitro allowed identification of intrinsic motor neurones. Subsequently, their content of choline acetyltransferase and nitric oxide synthase, markers of acetylcholine and nitric oxide containing neurones, was established using immunohistochemical techniques. Organ bath pharmacology was used to evaluate neurotransmission by acetylcholine and nitric oxide in gall bladder muscle strips. RESULTS: Innervation of the gall bladder musculature by neurones of both the muscular and serosal plexuses was demonstrated. A large proportion (62%) of these motor neurones were immunoreactive for nitric oxide synthase. All gall bladder neurones showed immunoreactivity for choline acetyltransferase. Organ bath pharmacology confirmed the neuroanatomical data, showing acetylcholine and nitric oxide mediating neurotransmission to the gall bladder musculature. CONCLUSIONS: Neurones containing acetylcholine and nitric oxide, located within the muscular and serosal plexuses, provide excitatory and inhibitory motor innervation of the gall bladder, respectively. The large inhibitory innervation suggests active relaxation of the gall bladder during filling, mediated by intrinsic nerves.

Development of a sleeve sensor for measurement of sphincter of Oddi motility.

BACKGROUND AND STUDY AIMS: Unavoidable catheter movement during sphincter of Oddi (SO) manometry can produce considerable variations in the basal pressure, due to movement of the recording sidehole. The sleeve sensor is a perfused channel which records the highest pressure point along its length. The aim of the study was to develop and evaluate a prototype sleeve sensor for SO manometry. MATERIALS AND METHODS: Bench-testing was used to assess the dynamic performance of the sleeve and sidehole assemblies. Recordings were initially made with a standard triple-lumen catheter and then with a purpose-built manometric assembly which had a 15 mm long sleeve sensor. RESULTS: A perfusion rate of 0.04 ml/min gave the best balance between baseline pressure offset and rise rate. Recordings were attempted in nine patients and successfully achieved in four. The sleeve and sidehole recordings of the maximal basal pressure did not differ significantly (mean +/- SEM, 86.1 +/- 26.5 mmHg vs. 90.1 +/- 21.0 mmHg, P = 0.57, r = 0.998). CONCLUSIONS: Unnecessarily high perfusion rates are being used for SO manometry. The sleeve sensor has the potential to monitor SO pressure more reliably than the currently used perfused sidehole method and should enhance the safety of prolonged SO manometry.

Sphincter of Oddi dysfunction produces acute pancreatitis in the possum.

BACKGROUND: Sphincter of Oddi dysfunction has been implicated as a cause of various forms of acute pancreatitis. However, there is no direct evidence to show that sphincter of Oddi dysfunction can cause obstruction of trans-sphincteric flow resulting in acute pancreatitis. AIMS: To determine if induced sphincter of Oddi spasm can produce trans-sphincteric obstruction and, in combination with stimulated pancreatic secretion, induce acute pancreatitis. METHODS: In anaesthetised possums, the pancreatic duct was ligated and pancreatic exocrine secretion stimulated by cholecystokinin octapeptide/secretin to induce acute pancreatitis. In separate animals, carbachol was applied topically to the sphincter of Oddi to cause transient sphincter obstruction. Sphincter of Oddi motility, trans-sphincteric flow, pancreatic duct pressure, pancreatic exocrine secretion, plasma amylase levels, and pancreatic tissue damage (histology score) were studied and compared with variables in ligation models. RESULTS: Acute pancreatitis developed following stimulation of pancreatic exocrine secretion with peptides after pancreatic duct ligation (p<0.05). Neither pancreatic duct ligation nor stimulation of pancreatic exocrine secretion with cholecystokinin octapeptide/secretin alone resulted in acute pancreatitis. Topical carbachol stimulated sphincter of Oddi motility abolished trans-sphincteric flow, and increased pancreatic exocrine secretion (p<0.05) and pancreatic duct pressure to levels comparable with pancreatic duct ligation (p<0.001). Carbachol application (with or without combined peptide stimulation) elevated plasma amylase levels (p<0.01) and produced pancreatic tissue damage (p<0.05). Decompression of pancreatic duct ameliorated these effects (p<0.05). CONCLUSION: Induced sphincter of Oddi dysfunction when coupled with stimulated pancreatic secretion causes acute pancreatitis. This may be an important pathophysiological mechanism causing various forms of acute pancreatitis.

Proximal and distal segments of the possum sphincter of Oddi respond differently to neural and cholecystokinin octapeptide stimulation in vitro.

BACKGROUND/AIMS: Previous studies have demonstrated separate pancreatic duct (PD) and bile duct (BD) components of the sphincter of Oddi (SO) and suggested distinct proximal and distal functional segments. This study was designed to determine if proximal and distal segments of the BD component of the SO (BD-SO) and PD component of the SO (PD-SO) responded equally to (1) activation of SO-duodenal neural pathways, and (2) exogenous cholecystokinin octapeptide (CCK-8). METHODS: Intact SO-duodenum preparations from Australian brush-tailed possums (n = 6) were mounted in organ baths. SO activity was recorded from the proximal and distal segments of BD-SO and PD-SO +/- electrical activation of duodenal nerves at two separate sites. Full thickness muscle strips from the proximal and distal segments of the BD-SO and PD-SO were prepared (n = 8), mounted in organ baths, and exposed to CCK-8 (10(-9)- 10(-6) M), +/- tetrodotoxin. RESULTS: Activation of duodenal nerves evoked different responses in some segments of the BD-SO and PD-SO, depending on the site of duodenal electrical stimulation. CCK-8 induced a concentration-dependent, tetrodotoxin-insensitive decrease in the contraction amplitude of SO muscle strips from the proximal but not the distal SO. BD-SO and PD-SO strips were not different. CONCLUSIONS: The SO is composed of BD and PD components each of which contains proximal and distal segments that can respond independently to appropriate stimuli.

Delayed pudendal nerve conduction and endosonographic appearance of the anal sphincter complex.

PURPOSE: The aim of this study was to test the hypothesis that a delay in pudendal nerve conduction as measured by pudendal nerve terminal motor latency should be associated with atrophy of the external anal sphincter as measured using endoanal ultrasound. METHODS: Sixty-two adult females (median age, 58.9 (range, 22-88) years) presenting for evaluation of fecal incontinence with no evidence of an external anal sphincter tear on ultrasound were recruited. Ultrasound was performed with a 7.5-MHz radial rotating axial endoprobe in the left lateral position. Four measurements were made in the transverse plane--the external anal sphincter thickness in the midanal canal at the 6 o'clock and 9 o'clock positions, the internal sphincter at the 9 o'clock position, and the external anal sphincter in the low canal at the 9 o'clock position. Pudendal nerve terminal motor latency was measured using a transrectal nerve stimulation technique with measurement of the evoked muscle response. RESULTS: Although there was a trend toward thinner external sphincter muscles in those with bilateral prolonged pudendal nerve terminal motor latency, independent sample t-tests and Pearson correlation coefficients showed no statistically significant relationship (right pudendal nerve terminal motor latency: P = 0.083, 0.184, 0.128, 0.910; r = 0.228, 0.175, -0.201, -0.015; left pudendal nerve terminal motor latency: P = 0.946, 0.276, 0.510, 0.123; r = -0.009, -0.143, -0.087, -0.201). CONCLUSIONS: No statistically significant relationship between ultrasound-measured anal sphincter muscle thickness and pudendal nerve terminal motor latency was identified. Although a trend was suggested that could be further evaluated by a study with a larger sample size and a control group with asymptomatic patients, the small differences in muscle thickness involved and the difficulties in measurement suggest that the establishment of clinically useful ultrasound criteria for the detection of the neuropathic anal sphincter complex is unlikely.

Somatostatin stimulates the brush-tailed possum sphincter of Oddi in vitro and in vivo.

BACKGROUND & AIMS: Somatostatin, a neuropeptide and hormone, is found in the biliary tract of several species. The aim of this study was to map the distribution of somatostatin-like immunoreactive nerve fibers in the extrahepatic biliary tract of the Australian possum and to determine the pharmacological effects of somatostatin 1-14 on sphincter of Oddi activity in vitro and in vivo. METHODS: Tissue was harvested for immunohistochemistry and sphincter of Oddi for circular or longitudinal muscle contractility. In anesthetized possums, sphincter of Oddi motility was measured by manometry, and transsphincteric flow was measured gravimetrically. RESULTS: Somatostatin immunoreactivity was evident in gallbladder ganglia nerve cell bodies and in nerve fibers of the common bile duct and sphincter of Oddi. Somatostatin 1-14 increased circular and longitudinal muscle contraction amplitude 3-4-fold (P < 0.05), but only the longitudinal muscle contraction amplitude was tetrodotoxin sensitive. Somatostatin 1-14 stimulated spontaneous sphincter of Oddi motility in a tetrodotoxin-insensitive manner, increasing basal pressure, contraction frequency, and amplitude 2-4-fold (P < 0.05) and reducing transsphincteric flow to 25% of control (P < 0.0001). CONCLUSIONS: Somatostatin-like immunoreactivity is present in the extrahepatic biliary tree, and somatostatin 1-14 stimulates sphincter of Oddi smooth muscle and nerves. The major action is direct stimulation of sphincter of Oddi circular muscle, which reduces transsphincteric flow.

Gastrin-releasing peptide stimulates gallbladder motility but not sphincter of Oddi motility in Australian brush-tailed possum.

The neural distribution and action of gastrin-releasing peptide in the extrahepatic biliary tree of the Australian brush-tailed possum was investigated. Immunohistochemical staining of fixed specimens demonstrated gastrin-releasing peptide-containing nerves throughout the neural plexuses of the gallbladder, sphincter of Oddi, and mucosa of the common bile duct. Gastrin-releasing peptide (5-2000 ng/kg) increased gallbladder tone to a level equivalent to that produced by cholecystokinin octapeptide (160 ng/kg). This action was tetrodotoxin-insensitive. Sphincter of Oddi motility and transsphincteric flow were not altered. Possible mediation of the gallbladder response by gastrin was examined. Gastrin (50-2500 ng/kg) stimulated gastric acid secretion, elevated gallbladder motility to 64% of that produced by gastrin-releasing peptide, and did not alter sphincter of Oddi motility. In conclusion, gastrin-releasing peptide-containing nerves are found in the neural plexus of the possum extrahepatic biliary tree. Gastrin-releasing peptide induces gallbladder contraction in part by a direct action on gallbladder smooth muscle and also via release of gastrin.