Peptide immunoreactive nerves and cells of the guinea pig gall bladder and biliary pathways

Development of pancreatic islet cells in the extrahepatic bile ducts of rats with experimentally-induced metabolic syndrome

CONTEXT

There is data about the existence of some endocrine cells in the epithelial layer of the bile duct in humans and rats.

OBJECTIVE

We evaluated Ghrelin-, Insulin-, Glucagon- and Somatostatin-positive cells in peribiliary glands, mast cells, and nerve fibres.

MATERIALS AND METHODS

Wistar rats were used for dietary manipulation with a 15% fructose solution for 12 weeks. Tissue samples were elaborated with immunohistochemistry for Insulin, Glucagon, Ghrelin, and Somatostatin. Glucose and lipid parameters were studied.

RESULTS

In treated animals, Ghrelin+ and Insulin+ cells in perybiliary glands (PBGs) were significantly increased. In the male fructose group there was a significant increase of the homeostasis model assessment insulin resistance (HOMA-IR).

CONCLUSIONS

Stem/progenitor cells in extrahepatic bile tree (EHBT) could be a source of Insulin-producing cells in metabolic syndrome. Fructose treatment induces the increase of Ghrelin+ and Insulin+ cells in PBGs and the elevation of Insulin and Ghrelin plasma concentration.

The distribution and chemical coding of neurons supplying the sphincter of Oddi in mammals

The major duodenal papilla (papilla of Vater) is an important structure associated with the biliary tract and, in some species, the pancreas. It usually represents a slight elevation on the intestinal mucosa where the dilated junction (ampulla of Vater) of the commmon bile duct and pancreatic duct enters the duodenum. The ampulla is surrounded by a specifically arranged muscle structure called the sphincter of Oddi (SO) which controls the flow of bile and pancreatic fluid. The function of the sphincter is regulated by a complex system that involves many hormonal and neural factors. The literature in the field contains detailed data on the morphology of the SO in a number of mammalian species. However, the comprehensive information about the anatomy and neurochemistry of the innervation of this structure is very limited. The present review article summarizes the current knowledge on the innervation of the SO in mammals. Special emphasis has been put on the localization and chemical coding of neurons contributing to this nerve supply.

Effect of somatostatin on human sphincter of Oddi motility

Native somatostatin is a gut hormone and neuropeptide, widely distributed in the nervous and gastrointestinal system, and has a broad range of biological actions. In gastrointestinal tract (GIT), somatostatin is mainly produced by the delta cells of the pancreas and gastrointestinal mucosal. The inhibitory effects of somatostatin on gastrointestinal motility and hormone secretion are mediated by a family of G protein-coupled receptors: the somatostatin receptors (SSTR1-5). The sphincter of Oddi (SO) located near the duodenum papillae is an anatomically and functionally distinct organ, SO motility is controlled and regulated by nerve, hormone and interstitial cells of Cajal. The effect of somatostatin on SO motility is still controversial. This article reviewed effect of somatostatin on human sphincter of oddi motility.

Neural connections between the hypothalamus and the liver

After receiving information from afferent nerves, the hypothalamus sends signals to peripheral organs, including the liver, to keep homeostasis. There are two ways for the hypothalamus to signal to the peripheral organs: by stimulating the autonomic nerves and by releasing hormones from the pituitary gland. In order to reveal the involvement of the autonomic nervous system in liver function, we focus in this study on autonomic nerves and neuroendocrine connections between the hypothalamus and the liver. The hypothalamus consists of three major areas: lateral, medial, and periventricular. Each area has some nuclei. There are two important nuclei and one area in the hypothalamus that send out the neural autonomic information to the peripheral organs: the ventromedial hypothalamic nucleus (VMH) in the medial area, the lateral hypothalamic area (LHA), and the periventricular hypothalamic nucleus (PVN) in the periventricular area. VMH sends sympathetic signals to the liver via the celiac ganglia, the LHA sends parasympathetic signals to the liver via the vagal nerve, and the PVN integrates information from other areas of the hypothalamus and sends both autonomic signals to the liver. As for the afferent nerves, there are two pathways: a vagal afferent and a dorsal afferent nerve pathway. Vagal afferent nerves are thought to play a role as sensors in the peripheral organs and to send signals to the brain, including the hypothalamus, via nodosa ganglia of the vagal nerve. On the other hand, dorsal afferent nerves are primary sensory nerves that send signals to the brain via lower thoracic dorsal root ganglia. In the liver, many nerves contain classical neurotransmitters (noradrenaline and acetylcholine) and neuropeptides (substance P, calcitonin gene-related peptide, neuropeptide Y, vasoactive intestinal polypeptide, somatostatin, glucagon, glucagon-like peptide, neurotensin, serotonin, and galanin). Their distribution in the liver is species-dependent. Some of these nerves are thought to be involved in the regulation of hepatic function as well as of hemodynamics. In addition to direct neural connections, the hypothalamus can affect metabolic functions by neuroendocrine connections: the hypothalamus-pancreas axis, the hypothalamus-adrenal axis, and the hypothalamus-pituitary axis. In the hypothalamus-pancreas axis, autonomic nerves release glucagon and insulin, which directly enter the liver and affect liver metabolism. In the hypothalamus-adrenal axis, autonomic nerves release catecholamines such as adrenaline and noradrenaline from the adrenal medulla, which also affects liver metabolism. In the hypothalamus-pituitary axis, release of glucocorticoids and thyroid hormones is stimulated by pituitary hormones. Both groups of hormones modulate hepatic metabolism. Taken together, the hypothalamus controls liver functions by neural and neuroendocrine connections.

Identification of dorsal root ganglion neurons that innervate the common bile duct of rats

Pain originating in the bile duct is common and many patients who have suffered from it report that it is one of the most intense forms of pain that they have experienced. Many uncertainties remain about the mechanisms underlying pain originating in the bile duct. For example, the dorsal root ganglion (DRG) neurons that give rise to the sensory innervation of the common bile duct (CBD) have not been identified and examined in any species. The goal of the present study was to determine the number, distribution, and size of DRG neurons that innervate the CBD in rats. Injections of WGA-HRP or CTB-HRP were restricted to the lumen of the bile duct. Injections of WGA-HRP labeled a mean number of about 500 DRG neurons bilaterally throughout all thoracic and upper lumbar levels. Injections of CTB-HRP labeled smaller numbers of DRG neurons. Application of colchicine onto the surface of the CBD reduced the number of cells labeled following injections of WGA-HRP into the lumen of the CBD by roughly 86%, suggesting that tracer had not spread in large amounts out of the CBD and labeled afferent fibers in other tissues. Approximately 85% of the neurons labeled with WGA-HRP had cell bodies that were classified as small; the remainder were medium in size. Injections of CTB-HRP labeled cell bodies of varying sizes, including a few large diameter cell bodies. These results indicate that a large number of primarily small DRG cells, located bilaterally at many segmental levels, provide a rich innervation of the common bile duct.

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.

Opioid agonists inhibit excitatory neurotransmission in ganglia and at the neuromuscular junction in Guinea pig gallbladder

BACKGROUND & AIMS

Opiates administered therapeutically could have an inhibitory effect on the neuromuscular axis of the gallbladder, and thus contribute to biliary stasis and acalculous cholecystitis.

METHODS

Intracellular recordings were made from gallbladder neurons and smooth muscle, and tension measurements were made from muscle strips. Opioid receptor-specific agonists tested: delta, DPDPE; kappa, U-50488H; and mu, DAMGO.

RESULTS

Opioid agonists had no effect on gallbladder neurons or smooth muscle. Each of the opioid agonists potently suppressed the fast excitatory synaptic input to gallbladder neurons, in a concentration-dependent manner with half-maximal effective concentration values of about 1 pmol/L. Also, each agonist caused a concentration-dependent reduction in the amplitude of the neurogenic contractile response (half-maximal effective concentration values: DPDPE, 189 pmol/L; U-50488H, 472 pmol/L; and DAMGO, 112 pmol/L). These ganglionic and neuromuscular effects were attenuated by the highly selective opioid-receptor antagonist, naloxone. Opioid-receptor activation also inhibited the presynaptic facilitory effect of cholecystokinin in gallbladder ganglia. Immunohistochemistry with opioid receptor-specific antisera revealed immunostaining for all 3 receptor subtypes in nerve bundles and neuronal cell bodies within the gallbladder, whereas opiate-immunoreactive nerve fibers are sparse in the gallbladder.

CONCLUSIONS

These results show that opiates can cause presynaptic inhibition of excitatory neurotransmission at 2 sites within the wall of the gallbladder: vagal preganglionic terminals in ganglia and neuromuscular nerve terminals. These findings support the concept that opiates can contribute to gallbladder stasis by inhibiting ganglionic activity and neurogenic contractions.

PHI-like immunoreactivity in the gallbladder and in vitro effect of porcine PHI on smooth muscle of the gallbladder

The occurrence and distribution of PHI-like immunoreactivity in the guinea pig gallbladder has been analysed by radioimmunoassay and immunocytochemistry. Chromatography of gallbladder extracts by gel permeation and high-performance liquid chromatography revealed that guinea pig PHI-like immunoreactivity is of a similar size to that of porcine PHI but may differ in its amino acid sequence. Immunocytochemistry showed PHI-immunoreactivity to be localised to nerves found predominantly in the ganglionated plexus and the mucosal plexus of the gallbladder. Pure natural porcine PHI induced a dose-dependent relaxation of the isolated guinea pig gallbladder muscle which was not blocked by antagonists to acetylcholine, catecholamines, histamine, and 5-hydroxytryptamine. PHI may thus be one of the local factors involved in controlling gallbladder function.

Pathophysiology of the intrahepatic biliary epithelium

The intrahepatic bile duct epithelium modulates the fluidity and alkalinity of the primary hepatocellular bile from which it reabsorbs fluids, amino acids, glucose and bile acids, while secreting water, electrolytes and immunoglobulin A. The transport function of the intrahepatic biliary epithelium is finely regulated by a number of gastrointestinal hormones, neuropeptides and neurotransmitters that promote either secretion or absorption. The intrahepatic biliary epithelium appears to be a primary target in a broad group of chronic cholestatic disorders that represent an important cause of morbidity and mortality. The spectrum of cholangiopathies ranges from conditions in which a normal epithelium is damaged by disordered autoimmunity, infectious agents, toxic compounds or ischaemia, to genetically determined disorders arising from an abnormal bile duct biology, such as cystic fibrosis or biliary atresia. Probably as a result of the known heterogeneity in cholangiocyte function, different portions of the biliary tree appear to be preferentially affected in specific cholangiopathies. From a pathophysiological point of view, cholangiopathies are characterized by the coexistence of cholangiocyte loss (by apoptotic or lytic cell death) with cholangiocyte proliferation and various degrees of portal inflammation, fibrosis and cholestasis. These basic disease mechanisms are discussed in detail. Better understanding of cholangiocyte pathophysiology, in particular the immune regulation of cholangiocyte function, will help in designing newer genetic or pharmacological approaches to treat cholangiopathies.

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.

Substance P stimulates sphincter of Oddi motility and inhibits trans-sphincteric flow in the Australian brush-tailed possum

Substance P containing nerves are widely distributed throughout the gastrointestinal tract. The aims of this study were to determine the distribution of substance P containing nerves in the extrahepatic biliary tree of the Australian brush-tailed possum and to characterize the effect of exogenous substance P on the sphincter of Oddi (SO) motility and transphincteric flow in vivo. Immunohistochemical staining of fixed specimens (n = 8) found moderate numbers of substance P containing nerve cell bodies and fibres throughout the neural plexuses of the SO, in particular in the serosal and intraluminal nerve trunks of the SO and gallbladder. Synthetic porcine substance P (1-2000 ng kg-1), administered by close intra-arterial injection (i.a.; n = 7), produced a dose-dependent elevation in basal pressure [P < 0.01] and an associated dose-dependent reduction in trans-sphincteric flow [P < 0.0001]. Substance P had no significant dose-dependent effect on SO phasic contraction amplitude or frequency. Tetrodotoxin (9 micrograms kg-1, i.a.) did not inhibit the effect of substance P on SO motility and trans-sphincteric flow (n = 5). In conclusion, substance P containing nerves are found throughout the possum extrahepatic biliary tree. Exogenous substance P stimulates SO motility and reduces trans-sphincteric flow in vivo by acting directly on the sphincter smooth muscle.

Tachykinins in the gut. Part I. Expression, release and motor function

The preprotachykinin-A gene-derived peptides substance P and neurokinin (NK) A are expressed in distinct neural pathways of the mammalian gut. When released from intrinsic enteric or extrinsic primary afferent neurons, tachykinins have the potential to influence both nerve and muscle by way of interaction with three different types of tachykinin receptor, termed NK1, NK2 and NK3 receptors. Most prominent among the effects of tachykinins is their excitatory action on gastrointestinal motor activity, which is seen in virtually all regions and layers of the mammalian gut. This action depends not only on a direct activation of the muscle through NK1 and/or NK2 receptors, but also on stimulation of excitatory enteric motor pathways through NK3 and/or NK1 receptors. In addition, tachykinins can inhibit motor activity by stimulating either inhibitory neuronal pathways or interrupting excitatory relays. A synopsis of the available data indicates that endogenous substance P and NKA interact with other enteric transmitters in the physiological control of gastrointestinal motor activity. Derangement of the regulatory roles of tachykinins may be a factor in the gastrointestinal dysmotility associated with infection, inflammation, stress and pain. In a therapeutic perspective, it would seem conceivable, therefore, that tachykinin agonists and antagonists are adjuncts to the treatment of motor disorders that involve pathological disturbances of the gastrointestinal tachykinin system.

Gastrin-releasing peptide stimulates possum gallbladder contractility in vitro

Reports of the action of gastrin-releasing peptide (GRP) on gallbladder contraction are limited to a few species. We compared the action of GRP, acetyl gastrin-releasing peptide 20-27 (GRP 20-27), and cholecystokinin-octapeptide (CCK-8) on gallbladder contractility with and without pretreatment with the neural inhibitor tetrodotoxin (TTX) and the bombesin antagonist [D-Phe 6, Des-Met 14]-bombesin 6-14 ethylamide (BBS 6-14 E). Full-thickness muscle strips were prepared and suspended in organ baths. The maximum GRP, GRP 20-27, and CCK-8 responses were 54.2 +/- 4.2%, 74.6 +/- 6.4%, and 69.3 +/- 6.9% of that of carbachol, respectively. Pretreatment with TTX influenced the action of GRP 20-27, and pretreatment with BBS 6-14 E influenced that of GRP and GRP 20-27. These studies show that GRP and GRP 20-27 are potent agonists of gallbladder contractility, acting via GRP-preferring receptors, and that GRP 20-27 also acts via a neural component.

Peptidergic innervation of the human gallbladder

The human gallbladder was investigated by means of immunohistochemical methods for the occurrence of peptidergic nerve fibres. In the gallbladder 11 types of peptidergic nerve fibres were observed. These were somatostatin-, pancreatic polypeptide (PP)-, peptide YY (PYY)-, neuropeptide Y (NPY)-, vasoactive intestinal peptide (VIP)-, gastric inhibitory peptide (GIP)-, neurotensin-, cholecystokinin (CCK)/gastrin C-terminus, substance P-, galanin- and serotonin-immunoreactive nerve fibres. NPY- and GIP-containing neurones were occasionally observed in the ganglionated plexus in the fibromuscular coat. Somatostatin-, NPY-, neurotensin-, and galanin-immunoreactive nerve fibres were abundant. The other nerve fibres were few. Peptidergic nerve fibres occurred in the lamina propria mucosae around and in close contact with the basement membrane of the epithelial cells. In the fibromuscular coat, they lied mainly around the muscle bundles. They showed no special arrangement in the perimuscular connective tissue. In both arteries and veins somatostatin-, neurotensin, and galanin nerve fibres were detected in both tunica media and tunica adventitia. NPY-nerve fibres were found in tunica media and substance P- and GIP- nerve fibres in tunica adventitia. The peptidergic nerve fibres observed in the gallbladder outnumbered those observed with the peripheral nerve markers used in this study. It has been speculated that this might be due to the coexistence of several neuropeptides in the same nerve fibre and/or the coexistence of these neuropeptides with a classical neurotransmitter.

Calcitonin gene-related peptide innervation of the rat hepatobiliary system

The digestive system is densely innervated by calcitonin gene-related peptide (CGRP)-immunoreactive neurons. The present study investigated a) the distribution and origin of CGRP-immunoreactive fibers in the rat hepatobiliary tract, and b) their relation with substance P/tachykinin (SP/TK) immunoreactivity using immunohistochemical and radioimmunoassay techniques. CGRP-containing fibers form dense networks in the fibromuscular layer of the biliary tree and surrounding the portal vein. Thin, varicose fibers are present at the base of the mucosa of the ducts. In the liver, labeled fibers are restricted to the portal areas and the stromal compartment. Neonatal treatment with capsaicin, a neurotoxin for primary afferent neurons, or celiac/superior mesenteric ganglionectomy depletes CGRP-containing fibers in the biliary tract, and reduces those associated with the portal vein. In contrast, subdiaphragmatic vagotomy does not appreciably modify the density of these fibers. Radioimmunoassay studies show a reduction of CGRP-immunoreactive contents in the biliary tract and portal vein by 84% and 65%, respectively, following capsaicin treatment, and by 80% and 66%, respectively, following ganglionectomy. By contrast, CGRP concentrations in vagotomized animals are comparable to those of controls. Most CGRP-positive fibers appear to contain SP/TK immunoreactivity, as indicated by double-label studies. These results demonstrate that the rat hepatobiliary tract is prominently innervated by CGRP- and CGRP/SP/TK-immunoreactive fibers, which are likely to originate from spinal afferent neurons. The abundance of these fibers and their association with a variety of targets are in line with the involvement of these peptidergic visceral afferents in regulating hepatobiliary activities, including hemodynamic functions of the hepatic vasculature.

Immunohistochemical identification of neurons in ganglia of the guinea pig sphincter of Oddi

The sphincter of Oddi is a smooth muscle sphincter that regulates the flow of bile into the duodenum. To identify potential chemical coding in sphincter of Oddi neurons, immunohistochemistry and histochemistry were employed to assay for putative neurotransmitters and related synthetic enzymes in wholemount preparations, with and without colchicine treatment. Immunoreactivities for enkephalin-endorphin (ENK-END), substance P (SP), nitric oxide synthase, vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), and calcitonin gene-related peptide (CGRP) were demonstrated within the ganglionated plexus. Roughly half of the neurons in the sphincter of Oddi expressed immunoreactivity for both SP and ENK-END, but not for nitric oxide synthase. About 25% of the neurons expressed nitric oxide synthase immunoreactivity as well as NADPH-diaphorase activity. This contingent of neurons was made up of two subgroups: one that expressed immunoreactivity for VIP, the other for NPY. Neurons that expressed CGRP immunoreactivity were sparse in sphincter of Oddi ganglia; however, many axons immunoreactive for both CGRP and SP were present in the ganglionated plexus. The CGRP/SP fibers are probably visceral afferents that may influence ganglionic output through axon reflex circuits. These results, along with studies of the actions of these neuroactive compounds on sphincter tone, support the view that ganglia of the sphincter of Oddi are largely comprised of excitatory (SP/ENK-END-immunoreactive) and inhibitory (nitric oxide synthase/VIP- or NPY-immunoreactive) neurons, and that sphincter of Oddi tone is controlled by the regulation of the outputs of these two groups of cells.

Peptide immunoreactivities in the ganglionated plexuses and nerve fibers innervating the human gallbladder

The mammalian gallbladder is innervated by a well-developed intrinsic neural network. However, little is known about the neurochemistry and organization of the innervation of this organ in humans. The aim of this study was to analyze the distribution of immunoreactivity (IR) for the neuropeptides, vasoactive intestinal polypeptide (VIP), neuropeptide Y (NPY), tachykinins (TK) and calcitonin gene-related peptide (CGRP) in the human gallbladder by means of immunohistochemistry. Neuropeptide-IRs are found in neurons and processes of the two ganglionated plexuses, i.e., the innermost plexus located in the lamina propria at the base of the mucosal folds, and the outermost plexus situated within the fibro-muscular layer. In these two plexuses, VIP-, NPY- and TK-IRs are present in ganglion cells and varicose fibers, whereas CGRP-IR is confined to nerve processes. VIP-IR is present in most, if not all, neurons. NPY- and TK-IRs are also found in many neurons. The densities of the peptide-IR nerves in the mucosa are NPY and VIP > TK >> CGRP, and in the fibro-muscular layer are NPY > VIP and TK > CGRP. The vasculature is richly innervated by NPY-IR nerves, which are mostly perivascular. CGRP-, VIP- and TK-IR processes are found only occasionally around blood vessels and in a paravascular position. Double-label studies demonstrated that a large number of VIP-containing neurons expresses NPY- or TK-IR. On the other hand, all neurons positive for either NPY- or TK-IR are immunostained for VIP. In agreement with these findings, most of the NPY-IR fibers in the lamina propria and fibro-muscular layer contain VIP-IR, and numerous TK-IR fibers are positive for VIP. However, the perivascular NPY-IR processes do not contain VIP-IR, suggesting an extrinsic origin. In addition, a population of TK-IR processes contains CGRP-IR and presumably originates from extrinsic sources, since CGRP/TK-IR intrinsic neurons could not be detected in the gallbladder. Peptide-IRs have a similar distribution in the neck, body and fundus of the gallbladder. No peptide-containing endocrine/paracrine cells are observed in the epithelium. The presence of peptide-IRs in the ganglionated plexuses and the abundance of peptidergic innervation suggest that peptides exert their effects on gallbladder function by acting directly on tissue targets and influencing intrinsic ganglion cells. Furthermore, the co-localization of more than one peptide in the same neuron raises the possibility that peptides are co-released upon stimulation and might interact at the same target.

The distribution and colocalization of neuropeptides and catecholamines in nerves supplying the gall bladder of the toad, Bufo marinus

The indirect immunofluorescence technique was used to determine the distribution of peptide-containing axons in the gall bladder of the cane toad, Bufo marinus. In addition, the adrenergic innervation of the gall bladder was examined by use of immunoreactivity to the catecholamine-synthesizing enzyme, tyrosine hydroxylase, and glyoxylic acid-induced fluorescence. On the basis of peptide coexistence, two intrinsic populations of neurones and their projecting fibres could be distinguished substance P neurones and vasoactive intestine peptide neurones. Neither of these two types of neurones contained any other colocalized neuropeptides. Four populations of nerve fibres arising from cell bodies outside the gall bladder were identified: nerves containing colocalized galanin, somatostatin and vasoactive intestinal peptide; nerves containing colocalized calcitonin gene-related peptide and substance P; adrenergic nerves containing neuropeptide Y; and nerves containing only adrenaline.

Peptidergic innervation of human sphincter of Oddi

The innervation of the sphincter of Oddi (SO) has been extensively studied experimentally, but human studies have not been published, which is why this study was undertaken. Biopsies, taken by gastroscopy-biopsy forceps from duodenal epithelium of the papilla of Vater and from ampullary epithelium after sphincterotomy, did not demonstrate nerves and could not be used for studying SO innervation. Therefore SO specimens were obtained from brain-dead organ donors (N = 5) and from autopsies (N = 14). By staining with a myelin marker S-100, a rich network of nerves was demonstrated in SO. The occurrence of vasoactive intestinal polypeptide (VIP), peptide histidine-isoleucine (PHI) (or its immunologically similar human equivalent peptide histidine methioninamide, PHM), neuropeptide Y, calcitonin gene-related peptide (CGRP), galanin, substance P, enkephalin, bombesin, and somatostatin were studied by immunohistochemical technique. SO demonstrated immunoreactivity for VIP, PHI (PHM), neuropeptide Y, CGRP, galanin, somatostatin, substance P, and enkephalin, but no immunoreactivity was observed for bombesin. The SO immunoreactivity was similar in specimens from organ donors and from autopsies of victims of violence without pancreatobiliary diseases (N = 3) when the specimens were taken within 48 hr of death. Autopsy specimens of SO from subjects with gallstone disease (N = 5), recurrent pancreatitis (N = 3) or periampullary carcinoma (N = 3) also demonstrated similar immunoreactivity. We conclude that VIP-, PHI- (PHM-), neuropeptide Y-, CGRP-, galanin-, substance P-, somatostatin-, and enkephalin-like immunoreactivity occur in human SO. These neuropeptides may have role in the neural control of human SO function.

Physiology of motor function of the sphincter of Oddi

Human and experimental studies of the sphincter of Oddi have established that the sphincter is not a simple and passive smooth muscle portion of the biliary system; rather, it plays an active role in modulating bile flow into the duodenum in both the fasted and the postprandial states. The sphincter of Oddi in the opossum, and likely in man, demonstrates spontaneous phasic and perhaps peristaltic activity that affects bile flow into the duodenum. The sphincter appears to be under the control of a smooth muscle pacemaking-like region in the proximal sphincter that controls the frequency and direction of propagation of the phasic contractions. Immunohistochemical studies have documented the presence of dense concentrations of neuropeptide-containing myenteric nerves in the sphincter of Oddi. Physiologic studies have confirmed that these peptides, in combination with the classic gastrointestinal hormones, exert significant effects on biliary motility. Experimental studies of the motor physiology of the sphincter of Oddi have advanced our understanding of human biliary motility and dysmotility. A subset of patients experiences biliary-like pain after cholecystectomy. This pain may be attributable to either mechanical stenosis of the papilla or dysfunction of the sphincter of Oddi. No definitive test currently exists to establish the diagnosis with adequate sensitivity or specificity. It is hoped that further development of ultrasonographic, scintigraphic, manometric, or electromyographic techniques will allow a clearer definition of patients who truly have sphincter dysfunction and who might benefit from medical, endoscopic, or surgical therapy.

Peptidergic innervation and endocrine cells in the human liver

Histologically normal liver biopsy specimens from patients with Hodgkin's lymphoma were investigated with three immunohistochemical methods for the occurrence of peptidergic nerve fibers and endocrine cells. Numerous immunoreactive nerve fibers were seen with antisera against peripheral nerves markers (neuron-specific enolase, neurofilament protein, and S-100). These nerve fibers were localized in the tunica media of branches of both the hepatic artery and portal vein, around the bile ducts, and in the connective tissue of the interlobular septa. In the liver, 10 types of peptidergic nerve fibers were detected: glucagon-, glucagon-like peptide- (GLP), somatostatin-, neuropeptide Y- (NPY), vasoactive intestinal polypeptide-, neurotensin-, gastrin/cholecystokinin C-terminus-, substance P-, serotonin-, and galanin-immunoreactive nerve fibers. GLP-, somatostatin-, NPY-, neurotensin-, substance P-, and galanin-immunoreactive nerve fibers were abundant; the other nerve fibers were scarce. The nerve fibers showed two distinct patterns of distribution: they occurred in the blood vessel wall and in connective tissue of the interlobular septum. Pancreatic polypeptide- and NPY-immunoreactive cells were found among the lining epithelial cells of the bile ducts in the interlobular septum.

Neuropeptides in pig sphincter of Oddi, bile duct, gallbladder, and duodenum

To better understand the complex structure and function of the sphincter of Oddi (SO), the occurrence and localization of nine neuropeptides, including vasoactive intestinal polypeptide (VIP), bombesin, neuropeptide Y, peptide histidine-isoleucine (PHI), calcitonin gene-related peptide (CGRP), galanin, substance P, serotonin, and somatostatin, were studied by immunohistochemical methods in the pig SO. The SO innervation was compared to gallbladder, common bile duct, and duodenal innervation. Specimens from the SO, gallbladder, common bile duct, and duodenum demonstrated a rich network of nerves, as suggested by light microscopy and confirmed by a myelin marker S-100. SO demonstrated very strong immunoreactivity for VIP, strong immunoreactivity for neuropeptide Y and galanin, moderate immunoreactivity for PHI and CGRP, and borderline immunoreactivity for bombesin and substance P. Serotonin and somatostatin immunoreactivity was also observed, not in the nerves, but in some of the epithelial cells. The gallbladder innervation was virtually identical to the SO innervation, whereas common bile duct and duodenal innervation were slightly different. To our knowledge this is the first time that galanin- and PHI-like immunoreactivities have been observed in the SO. Our observations suggest that these peptides, along with VIP, neuropeptide Y, and CGRP, might play a role in the neural control of biliary motility.

Transmitter diversity in ganglion cells of the guinea pig gallbladder: an immunohistochemical study

Several neurotransmitters have been reported to exist in the ganglionated plexus of the guinea pig gallbladder. These include substance P, neuropeptide Y (NPY), calcitonin gene-related peptide, vasoactive intestinal peptide (VIP), acetylcholine, norepinephrine, serotonin, and dopamine. To determine which neuropeptides are intrinsic to gallbladder ganglia, we performed immunohistochemistry on colchicine-treated preparations. In separate, single-labeled preparations, a majority of neurons contained substance P-, NPY-, or somatostatin-like immunoreactivity. In double-labeled preparations, a large majority of the neurons that contained substance P-like immunoreactivity also contained NPY-like immunoreactivity and somatostatin-like immunoreactivity. Immunoreactivity for VIP was present in a small percentage of the gallbladder neurons which did not contain substance P-like immunoreactivity. Additional experiments were done to test for the presence of other compounds, known to exist in the neurons of the gut. Although immunoreactivity was found in control preparations of small intestine, the ganglionated plexus of the gallbladder lacked immunoreactivity for galanin, dynorphin, enkephalin, gastrin-releasing peptide, or gamma-aminobutyric acid. We conclude that ganglia of the guinea pig gallbladder contain at least two populations of neurons, based on transmitter phenotype. One of these populations appears to contain substance P, NPY, and somatostatin. Another population, which represents a small contingent of the total population of neurons, contains VIP.

Structure of neurons and ganglia of the guinea pig gallbladder: light and electron microscopic studies

This study was undertaken to examine the morphological features of cells within ganglia of the guinea pig gallbladder, and to examine the ultrastructure of the ganglionated plexus. Gallbladder neurons are large, with a relatively simple form, having only one or two major processes. Neurobiotin often filled axons to their varicose arbors on smooth muscle in close proximity to the interganglionic connectives. With the exception of connective tissue clefts that sometimes penetrated into them, ganglia were devoid of intercellular spaces, capillaries, or connective tissue elements such as collagen and basal laminae. However, ganglia were surrounded by a single, continuous basal lamina that was enclosed within a fibroblast and collagen capsule. Within ganglia, neurons were insulated by the processes of cells that resembled the astrocyte-like glia of enteric ganglia. Although few classical synapses were observed, numerous sites of direct apposition were identified between vesicle-rich profiles and processes of gallbladder neurons. Direct appositions between vesicle-rich profiles and the ganglion-limiting basal laminae were also observed. Vesiculated profiles contained small clear vesicles and large dense-core vesicles. Within interganglionic connectives, axons were unmyelinated and were isolated from one another by processes of glia that resembled Schwann cells. As was seen in the ganglia, direct appositions between vesicle-rich profiles and the connective-limiting basal laminae were observed. The results of this study demonstrate that gallbladder ganglia are similar, ultrastructurally, to enteric ganglia in the CNS-like composition of the neuropil. However, the greater degree of glial investment, lesser degree of innervation, and simpler neurons indicated differences from the enteric nervous system that may be functionally significant.

Distribution of opioidergic, sympathetic and neuropeptide Y-positive nerves in the sphincter of Oddi and biliary tree of the monkey, Macaca fascicularis

The opioidergic, sympathetic and neuropeptide Y-positive innervation of the sphincter of Oddi (common bile duct sphincter and pancreatic duct sphincter), as well as other segments of the extrahepatic biliary tree was studied in the monkey by use of immunohistochemistry. Methionine-enkephalin-positive nerves were seen to innervate the smooth muscle of all portions of the sphincter of Oddi and also local ganglion cells. No methionine-enkephalin-positive nerves could be detected in the common bile duct, pancreatic duct or gallbladder. Tyrosine hydroxylase-positive nerves occurred between smooth muscle bundles and also ran to local ganglion cells as well as along the common bile duct. Neuropeptide Y-positive nerves were observed within smooth muscle of the sphincter of Oddi (all portions), common bile duct, pancreatic duct and gallbladder. No evidence of any differential innervation of the pancreatic duct and common bile duct sphincters could be detected with these markers.

Biliary tract motor dysfunction

Gallbladder and sphincter of Oddi motility regulates the flow of bile from the liver to the duodenum. During the interdigestive period most secreted bile is diverted into the gallbladder where it is concentrated, but a significant minority of the biliary secretion passes directly into the duodenum. Regulation of this flow is mainly via the phasic contractions of the sphincter of Oddi and the sphincter basal tone. The phasic contractions expel small volumes of fluid into the duodenum, but most of the flow occurs between the contractions and is therefore not dependent on peristaltic pumping, but rather on a small pressure gradient. During fasting, just prior to duodenal phase III activity, the gallbladder expels up to 40% of its volume and the sphincter phasic contractions increase. Following a meal, the gallbladder empties its contents, and the sphincter of Oddi resistance is reduced via a fall in basal pressure and inhibition of the amplitude of phasic contractions. Control of this activity is via an interplay of both neuronal and hormonal factors which together have an effect on both gallbladder and sphincter of Oddi motility. Abnormalities in motility are recognized for both the gallbladder and the sphincter of Oddi. Gallbladder dyskinesia is objectively diagnosed using the radionuclide GBEF. In patients with a GBEF less than 40% cholecystectomy results in relief of symptoms. In postcholecystectomy patients sphincter of Oddi dysfunction presents as either biliary-like pain or idiopathic recurrent pancreatitis. Endoscopic sphincter of Oddi manometry provides the most objective diagnostic information. In patients with a sphincter of Oddi stenosis, characterized manometrically as an elevated basal pressure, division of the sphincter results in relief of symptoms. For patients with biliary-like pain, division is performed as an endoscopic sphincterotomy, whereas for patients with idiopathic recurrent pancreatitis, a sphincteroplasty and pancreatic duct septectomy are required.

Innervation of the sphincter of Oddi: physiology and considerations of pharmacological intervention in biliary dyskinesia

The sphincter of Oddi is a small sphincter which is strategically placed at the junction of the bile duct and pancreatic duct with the duodenum. It regulates the flow of bile and pancreatic juice into the duodenum and prevents reflux of duodenal contents into the ducts. The structure of the sphincter of Oddi differs from species to species and consequently its physiological action varies in different species. Anatomical and immunohistochemical investigations have demonstrated that the sphincter of Oddi is richly innervated by cholinergic, adrenergic and peptidergic neurons. In addition, neural connections exist between the sphincter, gallbladder and proximal gastrointestinal tract. These nerves in addition to hormones are important in the control of sphincter of Oddi motility and function. The normal human sphincter of Oddi is characterized by prominent phasic contractions which are superimposed on a modest basal pressure. These contractions are present throughout the interdigestive period. The contractions and basal pressure are inhibited by ingestion of a meal or infusion of cholecystokinin octapeptide, thus enhancing the flow of bile and pancreatic juice into the duodenum. Sphincter of Oddi dysfunction has been described in patients who present with recurrent biliary type pain and no evidence of a structural cause for the pain. Motility disorders characterized as an elevated basal pressure, rapid contraction frequency, paradoxical response to cholecystokinin octapeptide or excess of retrograde contractions have been identified. A number of pharmacologically active substances have been used in an attempt to treat these patients. Such pharmaceuticals include nitrites, Ca2+ channel blockers and smooth muscle relaxants. Their effect is transient and side effects relating to cardiovascular actions preclude their longterm use. Division of the sphincter either endoscopically or by open operation has been demonstrated by prospective clinical trials to be the most efficacious treatment for patients with a stenosed sphincter manometrically demonstrated by a high basal pressure. Improved understanding of the controlling mechanisms of sphincter of Oddi motility and the pathophysiology of sphincter of Oddi dysfunction should assist in the development of effective pharmacotherapy for these disorders.

Substance P stimulates the opossum sphincter of Oddi in vitro

We have previously shown that substance P (SP) regulates sphincter of Oddi (SO) motility in vivo. However, its mechanism of action remains unclear. Our aim was to develop an in vitro model to measure spikeburst (SB) an contractile frequency (CMC) of the SO and to characterize further SP effects. In 16 opossums, SO rings were excised, mounted within a Kreb's tissue bath with bipolar electrodes and force transducers, allowed to equilibrate, and exposed to increasing SP concentrations with washout between each test solution. Spikeburst and CMC frequencies were recorded on a polygraph, quantitated, expressed as differences before and during SP, and statistically analyzed with Student's test. Although SP induced a significant concentration-dependent increase in phasic SB frequency and CMC, the amplitude of concentrations was not affected by SP. A close correlation was found between basal and SP-stimulated SB and CMC, suggesting myoelectric and mechanical coupling. Previous exposure of SO to SP antagonist [D-Arg1, D-Pro2, D-Trp7,9, Leu11]-SP significantly decreased the response to SP. Tetrodotoxin (TTX), did not affect the delta CMC response to SP. In conclusion an in vitro preparation was developed to study the effect of SP on the SO. Substance P increased SB and CMC of the SO in a concentration-dependent fashion, thus acting as a stimulatory peptide. Perfusion of SO rings with SP antagonist had no effect on basal CMC but significantly inhibited the action of SP in a competitive manner. The effect of SP was not altered by TTX. These data suggest that the action of SP on the SO is primarily myogenic.

Duodenal osmolality drives gallbladder emptying in humans

The effect of duodenal osmoreceptor stimulation on gallbladder motility was evaluated in 18 normal subjects during intraduodenal infusion of 280, 560 and 840 mosm/liters NaCl solutions. Gallbladder emptying was found to be dose-dependent between 560 and 840 mosm/liter (P less than 0.01 vs basal volume). The effect of duodenal infusion of hypertonic saline on gallbladder emptying was prevented by atropine and partially antagonized by naloxone, indicating that cholinergic and endorphinergic pathways may be involved in regulating this reflex. Since proglumide, a cholecystokinin (CCK) antagonist, did not affect gallbladder emptying induced by hypertonic saline, it seems likely that CCK is not released by increasing duodenal osmolality. A significant reduction in gallbladder volume was obtained when hyperosmolar saline was delivered into the duodenum, whereas no emptying was seen when infused into the gastric antrum or the jejunum, suggesting that osmoreceptors that activate gallbladder emptying are located only in the duodenum. Additionally, all subjects manifested central symptoms (nausea or vomiting) during duodenal infusion of hypertonic saline, suggesting that central mechanisms might be activated by a change in duodenal osmolality. Our data indicate that the osmolality of duodenal contents might regulate gallbladder motility by neural atropine- and naloxone-sensitive pathways.

Pathogenesis of acute cholecystitis after gastrectomy

The increased incidence of gallbladder diseases after gastrectomy is discussed with regard to contractile motility of the gallbladder. Ultrasonographic findings and contraction of the gallbladder in response to egg yolk or caerulein were studied before and after gastrectomy at intervals ranging from 2 weeks to 6 months. Enlargement of the gallbladder with accumulation of biliary sludge and hypomotility were frequently observed within a month of operation for gastric cancer, suggesting that biliary stasis is an important contributing factor in postoperative acute cholecystitis. Within 3 months of operation, contraction had recovered to close to preoperative levels and the incidence of biliary sludge formation gradually decreased. Daily administration of an opiate antagonist, naloxone (0.8 mg), significantly improved gallbladder dyskinesia and decreased the incidence of biliary sludge formation within 1 month of gastrectomy.

Nerve-mediated contractile and electrical activity of the guinea-pig choledocho-duodenal junction

The intrinsic motor innervation of the guinea-pig choledocho-duodenal junction was investigated by recording the contractile and intracellular electrical activity of smooth muscle from different regions of this tissue. Electrical transmural nerve stimulation evoked phasic contractions in rings of muscle from the ampulla (0.45 s-1) and tonic contractions in rings of muscle from the choledochal sphincter. Intracellular microelectrode recordings from muscle strips from these two regions revealed that excitatory junction potentials (peak amplitude 7 mV) evoked by transmural nerve stimulation were more conspicuous in muscle strips from the choledochal sphincter, but inhibitory junction potentials (peak amplitude 13 mV) were of larger amplitude in muscle strips from the ampulla. Contractions and membrane depolarization evoked by transmural nerve stimulation were sensitive to 1.4 microM atropine and abolished by 3.1 microM tetrodotoxin. Histological studies on the choledocho-duodenal junction also revealed that the distribution of smooth muscle was non-uniform along the tissue. These results suggest that the two regions may have different functions in the motility of the choledocho-duodenal junction.

Effect of thiorphan on response of the guinea-pig gallbladder to tachykinins

Tachykinins produced a concentration-related contraction of the isolated guinea-pig gallbladder, with a rank order of potency neurokinin A (NKA) greater than Arg-neurokinin B = neurokinin B (NKB) greater than substance P (SP). Only the effect of SP was potentiated by thiorphan (0.1-10 microM). A significant enhancement of the response to SP was also produced by captopril (1 microM). [Nle10]NKA-(4-10) and [beta-Ala8]NKA-(4-10), selective NK-2 receptor agonists, were active, whereas [Pro9]SP sulfone (selective NK-1 agonist) was almost ineffective. [MePhe7]NKB (selective NK-3 agonist) had some activity but only at high concentrations. Septide was almost ineffective and DiMeC7 had an action comparable to that of [MePhe7]NKB. None of the effects induced by these synthetic tachykinin analogs were significantly potentiated by thiorphan. Capsaicin (10 microM) produced a contraction which was unaffected by thiorphan. Both capsaicin and NKA-induced contractions were antagonized by Spantide at concentrations (5-10 microM) which had no effect against the atropine-sensitive contractions produced by electrical field stimulation. Capsaicin (1 microM) produced a consistent release of SP-like immunoreactivity (SP-LI) and a second application of the drug had no further effect, indicating complete desensitization. SP-LI release by capsaicin was almost doubled in the presence of thiorphan. These findings indicate that NK-2 and possibly some NK-3 receptors mediate the contractile response of the guinea-pig gallbladder to tachykinins. Both exogenous and endogenous (released by capsaicin) SP were degraded to a significant extent in this organ via a thiorphan-sensitive mechanism, the identity of which remains to be established.

Contractile response of canine gallbladder and sphincter of Oddi to substance P and related peptides in vitro

Substance P (SP) is a neurotransmitter peptide that is widely distributed in the body. Since SP has been demonstrated in the gallbladder (GB) and bile ducts of dogs, it may have a role in biliary motility. The objective of this study was to examine the effect of SP on the GB and sphincter of Oddi (SOD) of dogs in vitro, to evaluate the structure-activity relationship of SP, and to compare the contractile effect of SP with that of cholecystokinin octapeptide (CCK-8) and acetylcholine (Ach). Isolated longitudinal strips of GB and SOD from dogs were suspended in oxygenated Krebs buffer and the isometric tension responses to various doses of CCK-8, Ach, SP, and SP homologs [SP-free acid (SPFA), Octa-SP (O-SP), physalaemin (PHY)] were measured. We found that all the SP homologs, other than SPFA, stimulated GB and SOD contractions in vitro in a dose-dependent manner. The potency of SP and its homologs on GB and SOD was SP greater than or equal to PHY greater than O-SP; SPFA was without effect. CCK-8 was significantly more effective than SP on GB contraction, but unlike SP, CCK had no effect on SOD. The maximum contraction achieved by Ach was 1.3 (SOD) to 2.3 (GB) times greater than that achieved by SP, but the ED50 of SP was approximately 100- to 200-fold lower than that of Ach. The contractile effect of SP was partially blocked by 10(-5) M atropine.(ABSTRACT TRUNCATED AT 250 WORDS)

Structure, afferent innervation, and transmitter content of ganglia of the guinea pig gallbladder: relationship to the enteric nervous system

Although a well-developed plexus of nerves and ganglia is known to be present in the wall of the gallbladder, little has previously been learned about the function or organization of this innervation. The current study was undertaken in order to evaluate the hypothesis that the ganglionated plexus of the gallbladder is analogous to elements of the enteric nervous system (ENS). The ganglionated plexus of the gallbladder was found to resemble closely the submucosal plexus of the small intestine in its organization into two irregular anastomosing and interwoven networks of ganglia, in the numbers of neurons per ganglion, and in the manifestation of histochemically demonstrable acetylcholinesterase activity in virtually all ganglion cells. In common with enteric ganglia, laminin immunoreactivity was observed to be excluded from the interiors of gallbladder ganglia, which were surrounded by a periganglionic laminin-immunoreactive sheath. As in the submucosal plexus, intrinsic substance P-, vasoactive intestinal polypeptide (VIP)-, and neuropeptide Y (NPY)-immunoreactive neurons were seen in the ganglionated plexus of the gallbladder. Extrinsic nerves in the gallbladder that degenerated following chemical sympathectomy with 6-hydroxydopamine (6-OHDA), and which contained NPY, tyrosine hydroxylase (TH), and dopamine-beta-hydroxylase (DBH) immunoreactivities, formed a perivascular plexus closely associated with blood vessels. Endogenous catecholamines could also be demonstrated in these perivascular nerves by aldehyde-induced histofluorescence. In addition to perivascular nerves, paravascular nerve bundles were observed that were loosely associated with vessels, did not degenerate following administration of 6-OHDA, and contained NPY immunoreactivity. Other paravascular nerves, probably visceral sensory axons, coexpressed substance P and calcitonin-gene-related peptide (CGRP) immunoreactivities. The ganglionated plexus of the gallbladder resembled enteric ganglia in having intrinsic 5-hydroxytryptamine (5-HT)-immunoreactive cells and highly varicose nerve fibers. The 5-HT-immunoreactive gallbladder axons were, like those of the gut, resistant to 6-OHDA, and separate from fibers that expressed TH immunoreactivity. Differences between the ganglionated plexus of the gallbladder and enteric ganglia of the small intestine included in the gallbladder are 1) the presence of TH-immunoreactive cells that contain an endogenous catecholamine, but not DBH; 2) DBH-immunoreactive neurons, some of which coexpress substance P immunoreactivity, but which contain neither a catecholamine nor TH immunoreactivity; 3) an apparent absence of CGRP-immunoreactive cell bodies.(ABSTRACT TRUNCATED AT 400 WORDS)

Characterization of substance P effects on sphincter of Oddi myoelectric activity

We examined the effects of substance P (SP) on the myoelectric activity of the opossum sphincter of Oddi (SO). Myoelectric data from the SO in five adult opossums were recorded using thin stainless steel electrodes and computer-assisted analog-to-digital conversion. In fully awake and conscious animals, baseline spikeburst activity during phase I of the MMC occurred at a frequency of 28.6 +/- 3.1 spikebursts (SB) per 20-min period. Intravenous infusion of graded doses of substance P (from 0.5 to 8.0 micrograms/kg) stimulated SO myoelectric activity in a dose-related manner (from 80 +/- 8 to 235 +/- 11 SB/20 min, respectively, P less than 0.05 when compared to baseline). The effect of substance P on SO myoelectric activity was antagonized by administration of the H2-blocker, cimetidine (92.0 +/- 6.1 vs 48.2 +/- 7.0, n = 5, P less than 0.05). Administration of the antimuscarinic drug atropine only slightly affected the SO spikeburst frequency when infused prior to SP (73.0 +/- 10.4 vs 70.8 +/- 8.2, P greater than 0.05). We conclude that SP stimulated the SO spikeburst frequency in a dose-dependent fashion. Cimetidine markedly inhibited the response of the SO to SP but atropine did not. The excitatory effect of substance P on the opossum SO is mediated at least in part by a histaminergic, noncholinergic pathway.

Release of substance P- and calcitonin gene-related peptide-like immunoreactivity and motor response of the isolated guinea pig gallbladder to capsaicin

The aim of this study was to assess whether a local motor response to capsaicin could be observed in the isolated guinea pig gallbladder and to discover the mechanism involved. Capsaicin produced a contraction of this organ that exhibited desensitization, suggesting a specific action on sensory nerves. In preparations preexposed to capsaicin to produce a functional blockade of the capsaicin-sensitive sensory fibers, the contractile response to field stimulation was unaffected as compared with controls. Tachykinins (substance P and neurokinin A) produced a concentration-related contraction of this organ, neurokinin A being more potent than substance P. Spantide, a tachykinin antagonist, markedly inhibited the capsaicin-induced gallbladder contraction, leaving the atropine-sensitive response to field stimulation unaffected. Calcitonin gene-related peptide (CGRP) produced a concentration-related relaxation, which was tetrodotoxin-resistant, suggesting a direct effect on muscle cells. Repeated administration of CGRP produced desensitization. At this stage, application of capsaicin produced a contractile response much larger than in controls. Both substance P- and CGRP-like immunoreactivity were detected in the guinea pig gallbladder by radioimmunoassay and were significantly reduced after systemic capsaicin desensitization. Capsaicin induced the simultaneous release of substance P- and CGRP-like immunoreactivity from superfused isolated gallbladders. These findings indicate that capsaicin-sensitive nerves in the guinea pig gallbladder can produce a local motor response involving the release of multiple neuropeptides. In the guinea pig gallbladder, tachykinins and CGRP might act as "physiologic antagonists," as observed in other viscera from rats and guinea pigs.

Neuroendocrine innervation of the hepatic vessels in the rat and in man

An extensive array of nerve fibers ramify around the afferent blood vessels of the liver and the extrahepatic and intrahepatic biliary pathways, and are thought to be involved in regulation of blood flow. Although the role of sympathetic innervation is established, little is known about the location or role of regulatory peptidergic innervation in the liver. We examined the anatomic distribution of a wide variety of regulatory peptides and several neural antigens by in situ immunohistochemistry in the rat and in man. A rich peptidergic plexus of nerve fibers and ganglion cells was observed around the arterial vessels in both species, with intense immunoreactivity for neuron-specific enolase, neurofilaments, neuropeptide Y, substance P, and vasoactive intestinal polypeptide. S-100 protein immunoreactivity was seen principally in large nerve bundles, suggesting that the majority of nerves in this area were unmyelinated. In contrast, the portal vessels revealed very little peptidergic innervation. No staining was observed with antibodies directed against insulin, glucagon, gastrin, serotonin, met-enkephalin-Arg-Gly-Leu, cholecystokinin, or growth hormone. These findings indicate the presence of a rich, although selective, peptidergic plexus surrounding afferent hepatic blood vessels. This plexus may play an important role in regulation of hepatic blood flow.

Calcitonin gene-related peptide immunoreactivity in the biliary pathway and liver of the guinea-pig: distribution and colocalization with substance P

Calcitonin gene-related peptide immunoreactivity was localized immunohistochemically in nerve fibers innervating the biliary pathway and liver of the guinea-pig. Immunoreactive fibers are present in all layers of the gallbladder and biliary tract and are particularly numerous around blood vessels. In the liver, immunoreactive processes are usually restricted to the interlobular space and porta hepatis, and only a few, very thin, beaded processes were observed in the hepatic parenchyma. A rich innervation is also associated with the vena portae. Positive ganglion cell bodies were not visualized within the ganglionated plexus of the biliary system, whereas they were found in the myenteric and submucosal plexus in the cranial portion of the duodenum corresponding to the sphincter of Oddi. The vast majority, if not all, of calcitonin gene-related peptide-immunoreactive fibers contain substance P immunoreactivity; however, there are some substance P-containing fibers lacking calcitonin gene-related peptide immunoreactivity. The lack of co-occurrence of calcitonin gene-related peptide and substance P immunoreactivities in intrinsic ganglion cells suggests that these two peptides are coexpressed in the extrinsic component of the innervation of the hepatobiliary system.

The fine structure and histochemistry of human bile duct in obstruction and choledocholithiasis

Biopsies from the common bile ducts from seven patients undergoing surgery for biliary obstruction due to stones or malignancy were studied histochemically and electron microscopically. The surface of the bile duct is lined by a tall epithelium which extends into diverticula. Apically, they contain some neutral and sialated mucosubstances. Fucosyl residues were found in the Golgi apparatus and along the apical cell membrane. The latter is lined by microvilli. There was a well-developed rough endoplasmic reticulum and Golgi apparatus and a small number of apical secretory droplets. Large numbers of lipid droplets were present basally in some cells. Lipid-containing macrophages were also seen intra-epithelially and in the lamina propria. This suggests a possible pathway for lipid transport. The glands were lined by cuboidal cells, some containing much mucus--sulphated, sialated, and neutral with a basal nucleus. A well-developed endoplasmic reticulum and Golgi apparatus were found with abundant secretory droplets. The glandular epithelium contained lysozyme, alpha-1-antitrypsin, and alpha-1-antichymotrypsin. These may play a protective role. The lamina propria contained scattered smooth muscle cells amongst the fibroblasts and inflammatory cells.

Characterization of opioid receptors on isolated canine gallbladder smooth muscle cells

Smooth muscle cells were isolated from the fundus of the canine gallbladder and examined for the presence of opioid receptors. The cells contracted in a concentration-dependent manner in response to three opioid peptides (Met-enkephalin, dynorphin1-13 and Leu-enkephalin), which are known derivatives of opioid precursors present in myenteric neurons of the gut. The order of potency was Met-enkephalin greater than dynorphin1-13 greater than Leu-enkephalin. The contractile response to opioid agonists was selectively inhibited by opioid antagonists (naloxone and Mr2266) but not by muscarinic, CCK/gastrin or tachykinin antagonists. Equivalent responses to the three opioid peptides exhibited differential sensitivity to preferential antagonists of mu (naloxone) and kappa (Mr2266) opioid receptors consistent with the presence of the three main types of opioid receptors (mu, delta and kappa) on canine gallbladder muscle cells.

Identification and characterization of specific binding sites for somatostatin in cytosol of bovine cystic duct mucosa

Specific binding sites for somatostatin have been detected in cytosolic fraction of bovine cystic duct mucosa. At 37 degrees C, the interaction of 125I-Tyr11-somatostatin with cytosolic fraction was rapid, reversible, specific and saturable. At equilibrium, the binding of tracer was competitively inhibited by native peptide in the 1 nM to 2 microM range of concentrations. Scatchard analysis of binding data suggested the presence of two distinct classes of somatostatin binding sites: a class with a high affinity (Kd = 7.8 +/- 0.3 nM) and a low capacity (1.3 +/- 0.3 pmol somatostatin/mg protein) and a class with a low affinity (Kd = 129.1 +/- 2.0 nM) and a high capacity (43.5 +/- 6.7 pmol somatostatin/mg protein). The binding sites were shown to be highly specific for somatostatin since neuropeptides present in cystic duct such as Leu-enkephalin, neurotensin, substance P and vasoactive intestinal peptide did practically not show competition. These findings suggest that somatostatin could contribute to the regulation of the functions of the cystic duct mucosa in physiological and pathological conditions.

Specific somatostatin-binding to cytosol of bovine gallbladder mucosa

The binding of somatostatin was studied in the cytosolic fraction of bovine gallbladder mucosa. The binding reaction depended on time, temperature and pH, and was reversible, saturable and specific. Stoichiometric data suggested the presence of two classes of binding sites: a class with high affinity (Kd = 23.6 nM) and low capacity (3.7 pmol somatostatin/mg protein) and a class with low affinity (Kd = 284.6 nm) and high capacity (85.0 pmol somatostatin/mg protein) at 37 degrees C and pH 7.4. The binding sites were highly specific for somatostatin since peptides such as [Leu]enkephalin, neurotensin, vasoactive intestinal peptide and substance P showed practically no effect upon somatostatin binding. The presence of somatostatin-binding sites in the cytosolic fraction of gallbladder mucosa, together with the known occurrence of somatostatin nerve endings in the gallbladder strongly suggests that this peptide may be involved in the physiology and physiopathology of gallbladder mucosa.

Neuropeptide Y in the guinea-pig biliary tract

High concentrations of neuropeptide Y (NPY) have been demonstrated in the gall bladder (16.7 +/- 5.4 pmol/g), cystic duct (25.4 +/- 9.2 pmol/g) and common bile duct (54.7 +/- 11.5 pmol/g) of the guinea-pig using a recently developed radioimmunoassay. Immunoreactive NPY containing nerves were demonstrated in all layers of the biliary tree using immunocytochemistry, being particularly dense in the myenteric and mucosal plexuses.