The innervation of the human upper esophageal sphincter

The neuroanatomy and physiology of the human upper esophageal sphincter (UES) has long been controversial. As a result, there has been little progress in diagnosing and treating dysphagias involving this area. In this study, three specimens of the UES obtained from human autopsies were examined by Sihler's stain. This stain clears soft tissue while counterstaining the nerves, thereby allowing nerve supply to each muscle of the UES to be demonstrated. It was found that the nerve supply to each component of the UES is substantially different. The inferior pharyngeal constrictor (IPC) is supplied by a dense linear plexus which is about 1.0–1.5 cm wide and 10 cm long and located about 1.5 cm lateral to the attachment of the IPC on the thyroid lamina. The cricopharyngeal (CP) muscle receives its innervation from below via the recurrent laryngeal nerve (RLN) and from above via the pharyngeal plexus. Neural connections between the RLN and the pharyngeal plexus were observed. Finally, the upper esophagus (UE) is innervated by the RLN. The innervation pattern of each component of the UES suggests functional differences between these muscles. These observations help clarify the innervation of the UES. Accurate knowledge of the neuroanatomy of the UES is necessary for advances in diagnosis and treatment of pharyngeal dysphagia.     

Fecal incontinence induced by spontaneous internal anal sphincter relaxation: report of a case

It has been previously suggested that an increase in the frequency of internal anal sphincter relaxations may cause fecal incontinence in patients in whom a structural lesion of the anal sphincter or its nerve supply is not ruled out. We here report a case of fecal incontinence in which the sphincter and its innervation was not damaged, and prolonged recordings of anal resting pressure detected frequent and prolonged internal anal sphincter relaxations. Moreover, a spontaneous improvement in fecal incontinence occurred at the same time as a reduction in the frequency and duration of internal anal sphincter relaxations. This case suggests that prolonged recordings of anal resting pressure are advisable in incontinent patients without detectable lesions of the anal sphincter or its nerve supply to detect any increase in the frequency of internal anal sphincter relaxations as a possible cause of fecal incontinence.     

Role of intrahepatic innervation in regulating the activity of liver cells

Liver innervation comprises sympathetic,parasympathetic and peptidergic nerve fibers,organized as either afferent or efferent nerves with different origins and roles.Their anatomy and physiology have been studied in the past 30 years,with different results published over time.Hepatocytes are the main cell population of the liver,making up almost 80%of the total liver volume.The interaction between hepatocytes and nerve fibers is accomplished through a wealth of neurotransmitters and signaling pathways.In this short review,we have taken the task of condensing the most important data related to how the nervous system interacts with the liver and especially with the hepatocyte population,how it influences their metabolism and functions,and how different receptors and transmitters are involved in this complex process.     

心脏交感神经重构与心律失常:新兴领域的当前认识

心脏内交感神经纤维分布十分广泛,近年发现许多心脏疾病伴有交感神经分布、密度改变的现象,并与心律失常发生、疾病预后都有密切的关联。交感神经重构与心肌组织重构、电重构相互影响,可能是心律失常发生的基础。对交感神经重构进行干预可能成为将来新的一个治疗方向。     

Vasoactive intestinal peptide immunoreactive nerve fibres are deficient in intestinal and nasal mucosa affected by cystic fibrosis

Cystic fibrosis (CF) is the most common lethal or debilitating inherited disease amongst Caucasians, with estimates of its frequency of occurrence in this population ranging from 1: 2000 to 1: 15 000 live births. It is characterized by disorders of exocrine secretions, primarily of the skin, respiratory tract and digestive system. The secretory processes of these tissues are influenced by autonomic nerve fibres, many of which contain regulatory peptides. The innervation of the intestinal and respiratory mucosa of CF patients has been investigated in order to determine if there is any derangement of the peptide-containing nerve fibres that supply these tissues. The present work demonstrates that, in CF, there is a deficiency of vasoactive intestinal peptide immunoreactivity (VIP-IR) in nerve fibres in the nasal and intestinal mucosa. There is not a generalized loss of fibres that are immunoreactive for this peptide, however, since VIP-IR fibres innervating the intestinal muscle are largely unaffected. Moreover, other types of nerve fibres innervating the nasal mucosa and the mucosa of the intestinal villi appear to be unaffected in CF patients. Physiological evidence indicates that vasoactive intestinal peptide is contained in secretomotor neurons and is a powerful stimulant of secretion; loss of function restricted to these neurons is consistent with the clinical manifestations of CF.     

Autonomic Nervous System and the Liver

The liver is innervated by both the sympathetic and the parasympathetic nerve systems. These nerves are derived from the splanchnic and vagal nerves that surround the portal vein, hepatic artery, and bile duct. The afferent fiber delivers information regarding osmolality, glucose level, and lipid level in the portal vein to the central nervous system (CNS). In contrast, the efferent fiber is crucial in the regulation of metabolism, blood flow, and bile secretion. Furthermore, liver innervation has been associated with hepatic fibrosis, regeneration, and circadian rhythm. Knowledge of these mechanisms can be applied for potential liver disease treatment.     

Stromal mast cells and nerve fibers in various chronic liver diseases: relevance to hepatic fibrosis

OBJECTIVE: Recently, mast cells have been postulated to play a role in fibrogenesis in primary biliary cirrhosis (PBC) and alcoholic liver disease (ALD). There are only a few reports on nerve fibers in normal and pathological human livers. METHODS: We simultaneously investigated mast cells and nerve fibers in the stroma by single and double immunostainings and by quantitative morphometry in six normal livers and in 178 liver biopsies of PBC (n = 49), autoimmune hepatitis (n = 12), chronic hepatitis B (n = 37), chronic hepatitis C (n = 41), and ALD (n = 39). RESULTS: The densities of tryptase-positive mast cells, chymase-positive mast cells, and S-100-positive nerve fibers in the stroma were significantly higher in these chronic liver diseases than in normal livers. There were no significant differences in their densities among these chronic liver diseases. The densities of tryptase- and chymase-positive mast cells correlated significantly with degree of fibrosis, and density of nerve fibers correlated roughly with degree of fibrosis. Double immunostainings showed that some mast cells were in close contact with nerve fibers, and that, in selected cases, the percentages of mast cells positive for only tryptase (MC(T)) and those positive for both tryptase and chymase (MC(TC)) were 26% and 74%, respectively. CONCLUSIONS: These results suggest that mast cells and nerve fibers are involved in fibrogenesis in chronic liver diseases, regardless of their etiologies, probably by secreting fibrogenic substances. Some mast cells are innervated, and this innervation may stimulate mast cells to secrete fibrogenic substances, leading to hepatic fibrosis.     

Liver repopulation for the treatment of metabolic diseases

Orthotopic liver transplantation is the treatment of choice for several inborn errors of metabolism. Unfortunately, the supply of donor organs is limiting and therefore many patients cannot benefit from this therapy. In contrast, hepatocyte transplantation could potentially overcome the shortage in donor livers by use of cells from a single donor for multiple recipients. In classic hepatocyte transplantation, however, only 1% of the liver mass or less can be replaced by donor cells. Recently, though, it has been shown in animal models that >90% of host hepatocytes can be replaced by a small number of transplanted donor cells in a process we term 'therapeutic liver repopulation'. This phenomenon is analogous to repopulation of the haematopoietic system after bone marrow transplantation. Liver repopulation occurs when transplanted cells have a growth advantage in the setting of damage to recipient liver cells. It has been discovered that transplanted cells from extrahepatic sources such as the adult pancreas or bone marrow can also be used for liver repopulation. Because bone marrow donors are widely available, this finding raises the hope of therapeutic application of these cells in the future. Here, the current knowledge regarding therapeutic liver repopulation and the hopeful implications for treatment of liver diseases will be discussed.     

Hyperinnervation during adrenal regeneration influences the rate of functional recovery

The rat adrenal cortex has the uncommon ability to demonstrate morphological and functional regeneration after injury-induced loss of cortical tissue. Peripheral nerves are involved in tissue regeneration and healing after injury, implying that nerves may also be involved in modulating the regeneration of the adrenal cortex. Studies were initiated to assess changes in adrenal innervation during cortical tissue regeneration subsequent to adrenal enucleation. Innervation of regenerating adrenals was assessed from 3 to 62 days postenucleation by immunohistofluorescent detection of neuronal markers for primary afferent, preganglionic sympathetic, and postganglionic sympathetic fibers. The regenerating adrenal contained few nerves at 3 days postenucleation, but became differentially innervated, with extensive innervation by nerve fibers positive for calcitonin gene-related peptide (CGRP), tyrosine hydroxylase (TH), neuropeptide Y (NPY), and neuronal nitric oxide synthase (nNOS). In contrast, there was only minimal innervation by nerve fibers positive for vasoactive intestinal peptide. By 14 days postenucleation, the CGRP-, TH-, and NPY-positive innervation included areas of hyperinnervation in the capsule, cortex, and central inflammatory site of the regenerating gland. In addition, many chromaffin cells were present at all time points postenucleation. Quantification of the regenerating gland content of CGRP, norepinephrine, epinephrine, and nNOS verified the immunohistofluorescent observations. The period of extensive innervation correlated temporally with the time (3-30 days) during which the regenerating glands recovered steroidogenic function. Moreover, splanchnic nerve transection at the time of adrenal enucleation decreased the innervation by CGRP-positive and vesicular acetylcholine transporter-positive fibers and delayed regeneration. These results support the hypothesis that adrenal innervation modulates tissue regeneration and functional recovery of the enucleated adrenal gland.     

Widespread distribution of protein I in the central and peripheral nervous systems.

Protein I, a naturally occurring substrate for cyclic AMP-dependent and calcium-dependent protein kinases, previously has been found only in mammalian brain, where it has been demonstrated to be located in neurons. Various tissues and organs outside the brain have now been examined for the possible occurrence of protein I, by using both an immunohistochemical approach and a chemical procedure involving radioimmunolabeling of polyacrylamide gels. Protein I has been found in the inner plexiform layer of the retina, in the posterior pituitary, and in the autonomic nervous system. In tissue composed predominantly of cells other than nerve cells, immunoreactivity was present only where innervation was present. Protein I appeared to be localized in some, but not all, nerve terminals and synapses.     

Neuropeptide Y (NPY) and vasoactive intestinal polypeptide (VIP), but not galanin, are autonomic cotransmitters in the porcine pancreas.

The neuropeptide galanin has been identified as a potential sympathetic cotransmitter in the canine pancreas. Immunoreactive galanin, also present in nerve fibers of the pig pancreas, was therefore measured in the effluent from isolated perfused pig pancreas with preserved sympathetic (splanchnic) or parasympathetic (vagal) innervation with radioimmunoassays directed against both the N-terminus and the C-terminus of galanin. Electrical vagus stimulation increased the pancreatic exocrine secretion, the secretion of insulin and glucagon, and the release of VIP, but did not influence galanin release. Splanchnic nerve stimulation increased perfusion pressure and glucagon secretion, inhibited insulin secretion, and increased the release of NPY, but galanin release was not affected. We conclude that the pancreatic galanin nerve fibers belong neither to the sympathetic nor to the parasympathetic divisions of the efferent nerve supply to the pig pancreas.     

Nerve growth factor synthesis in vascular smooth muscle.

Details of the interdependent, trophic relation between smooth muscle and its neural innervation are not well known despite suggestions that neural influences may contribute significantly to hypertensive and other cardiovascular disease. Vascular smooth muscle is a major target of innervation by neurons of the sympathetic nervous system. Sympathetic neurons depend on a constant supply of the potent neurotrophic peptide nerve growth factor. Nerve growth factor regulates an impressive list of neuronal and perhaps muscle properties, yet its source in vessels and the determinants of its synthesis are not known. We have taken advantage of the cytoarchitecture of the aorta to demonstrate that vascular smooth muscle cells synthesize nerve growth factor. The survival of cultured sympathetic neurons is supported in a nerve growth factor-dependent manner by co-culture with pure rat aortic vascular smooth muscle cells. Furthermore, pure smooth muscle cell cultures contain nerve growth factor-specific messenger RNA. Levels of messenger nucleic acid coding for nerve growth factor in smooth muscle are regulated by contractile agonists (angiotensin II, arginine vasopressin) and the adrenergic agonist phenylephrine. This suggests a link between muscle activity and growth factor production. Secretion of nerve growth factor protein by vascular smooth muscle was measured using a sensitive two-site immunoassay. Secretion is highest during muscle growth. Secretion is elevated by angiotensin II and arginine vasopressin but slightly inhibited by phenylephrine. These results suggest that cultured vascular smooth muscle can serve as a useful model in which to study the cellular regulation of trophic factor synthesis in health and disease.     

The microvasculature in skeletal muscle. VI. Adrenergic innervation of arterioles in normotensive and spontaneously hypertensive rats.

A microanatomical study of the adrenergic nerve plexus on the arterioles in the spinotrapezius muscle of normotensive and spontaneously hypertensive rats was carried out. The spinotrapezius muscle was selected since its microvasculature has been reconstructed in previous studies of this series. A modified glyoxylic acid amine densification technique was used to visualize the major portion of the microvascular nerve plexus. The nerve plexus density was quantified in the form of fiber length per unit area of vascular smooth muscle media. The adrenergic innervation was found to be limited to the arterial/arteriolar side of the microcirculation and positioned in close vicinity to vascular smooth muscle, in line with previous reports. Substantial variations of the nerve plexus density could be detected along the arterioles. Arcade arterioles show a significant reduction of the adrenergic innervation compared to that of the thoracodorsal supply artery. There was a significant elevation of the nerve plexus density at the origin of the transverse arterioles at the arcade arterioles, a site that in the past has been shown to exhibit the highest microvascular tonus in all arterioles of this organ. Distal to this site, transverse arterioles exhibit a progressive reduction of adrenergic plexus density toward their capillary endings, in line with the termination of vascular smooth muscle in these small branches. Sporadic fiber extensions were encountered leading from some of the transverse arterioles into the capillary network per se, but no regular innervation was detected in capillaries or in venules. These results suggest that the transverse arterioles may play a central role in nervous control of blood flow to the capillaries of muscle. Compared with the Wistar and Wistar-Kyoto strain, the spontaneously hypertensive rats exhibit qualitatively a similar pattern, but show quantitatively a significantly higher plexus density in the thoracodorsal artery and the arcade arterioles, a factor that may contribute to the elevated arteriolar tone.     

Localization of cholinergic innervation in guinea pig heart by immunohistochemistry for high-affinity choline transporters

OBJECTIVE: Previous studies have used acetylcholinesterase (AChE) histochemistry to identify cholinergic nerves in the heart, but this enzyme is not a selective marker for cholinergic neurons. This study maps cholinergic innervation of guinea pig heart using a new antibody to the human high-affinity choline transporter (CHT), which is present only in cholinergic nerves. METHODS: Immunohistochemistry was used to localize CHTs in frozen and paraffin sections of heart and whole mount preparations of atrial ganglionated nerve plexus. AChE-positive nerve fibers were identified in sections from separate hearts for comparison. RESULTS: Control experiments established that the antibody to human CHT selectively labeled cholinergic neurons in the guinea pig. CHT-immunoreactive nerve fibers and AChE-positive nerves were very abundant in the sinus and AV nodes, bundle of His, and bundle branches. Both markers also delineated a distinct nerve tract in the posterior wall of the right atrium. AChE-positive nerve fibers were more abundant than CHT-immunoreactive nerves in working atrial and ventricular myocardium. CHT-immunoreactive nerves were rarely observed in left ventricular free wall. Both markers were associated with numerous parasympathetic ganglia that were distributed along the posterior atrial walls and within the interatrial septum, including the region of the AV node. CONCLUSIONS: Comparison of labeling patterns for CHT and AChE suggests that AChE histochemistry overestimates the density of cholinergic innervation in the heart. The distribution of CHT-immunoreactive nerve fibers and parasympathetic ganglia in the guinea pig heart suggests that heart rate, conduction velocity, and automaticity are precisely regulated by cholinergic innervation. In contrast, the paucity of CHT-immunoreactive nerve fibers in left ventricular myocardium implies that vagal efferent input has little or no direct influence on ventricular contractile function in the guinea pig.     

Electrical and hemodynamic function produced by stimulation of atropine sensitive right ventricular nerves in humans

In mammalian ventricles including humans, it is recognized that parasympathetic ganglia innervate the heart. Little is known about the location and function of right ventricular parasympathetic nerves in humans. We hypothesized that in humans: (1) there are parasympathetic ganglia that supply the right ventricle that can be stimulated via an endocardial catheter and (2) stimulation of these fibers will alter the electrical and hemodynamic function of the right ventricle. Parasympathetic nerve stimulation was performed via an endocardial catheter placed along several sites of the right ventricle, superior vena cava, and right internal jugular area in humans. The spatial extent of parasympathetic innervation was mapped in 1-cm zones across the right ventricle. Cardiac output, heart rate, and atrioventricular conduction were monitored to provide independent assessment of parasympathetic innervation. In all 22 patients, ventricular refractoriness shortened from 12 ± 3 to 3 ± 1 ms during parasympathetic nerve stimulation, and the greatest shortening of refractoriness was observed at the base of the right ventricle (p = 0.01). No significant shortening in ventricular refractoriness occurred in areas beyond 2 cm from the right ventricular base. These results were compared by using T table test. The parasympathetic nerve stimulation protocol decreased cardiac output, reaffirming the principle effect of parasympathetic ganglia. Atropine was administered in seven patients. All effects from nerve stimulation were abolished after atropine administration. These results were also compared by using T table test. These data provide the first demonstration of the electrical and hemodynamic function by stimulation of atropine sensitive nerves of the human right ventricle. Greater understanding of parasympathetic innervation may lead to novel therapies for arrhythmias.     

VIP-, substance P- and met-enkephalin-immunoreactive innervation of the human gastroduodenal mucosa and Brunner's glands.

VIP-, substance P- and met-enkephalin-containing innervation of the human gastroduodenal mucosa and Brunner's glands was studied by immunocytochemistry on whole mount tissue preparations. A dense VIP-containing nerve supply was found around fundic and pyloric glands, while the few and scattered substance P-immunoreactive fibres tended to run across the full thickness of the gastric mucosa. In the duodenum, both VIP and substance P were present in a striking nerve network in the villi as well as in the muscularis mucosae and around blood vessels. Both peptides were also immunostained in nerve bundles and neuronal perikarya between the lobules of Brunner's glands, while only very few fibres reached the proximity of acinar cells. Met-enkephalin-immunoreactivity was detected in a small number of nerve fibres, virtually confined to the basal parts of the mucosa and to the duodenal submucous plexus.     

Importance of the hepatic branch of the left vagus. Influence on lipid levels of regenerating liver in the rat

The influence of trunk and extrahepatic vagotomy on total lipid levels in the regenerating liver after partial hepatectomy (PH) was evaluated on Wistar rats. PH increased lipid levels in the liver, but after 24 h trunk vagotomy promoted a reduction in total liver lipids, which was prevented by the preservation of the hepatic branches of the left vagal nerve, leading to the conclusion that parasympathetic innervation of the liver has an important role on the mechanisms of maintenance of lipid levels.     

The effect of pinealectomy and autonomic denervation on crypt cell proliferation in the rat small intestine

Previously it has been found that pinealectomy in rats was associated with increased small bowel crypt cell proliferation. The hypothalamus is thought to play a role in the neural control of crypt cell proliferation and the pineal gland is known to be functionally connected with this component of the autonomic nervous system. Consequently, the effect on crypt cell mitotic rate of pinealectomy with autonomic denervation of the rat small bowel (local sympathectomy and truncal vagotomy) was observed to determine the possible importance of the autonomic nervous system in the mediation of the effects of pinealectomy on the crypts. It was found that interruption of either the vagal or sympathetic nerve supply to the small intestine both significantly decreased the usual hyperproliferative effect on the crypt cells observed after pinealectomy. It is suggested that the overall effect of the pineal gland is to suppress the crypt cell proliferation rate and that this effect is mediated, at least to some extent, by (1) the direct connections between the pineal gland and the hypothalamus, (2) the connections between the hypothalamus and the vagal and sympathetic innervation of the gut, and (3) the influence of the autonomic innervation on the activity of the enteric plexuses in relationship to the crypts. The pineal may have a role in modulating the local control mechanism of crypt cell proliferation. Its exact role in the control of crypt cell proliferation has not yet been defined.     

Treatment of hepatic fibrosis: Almost there

Hepatic fibrosis is the scarring response of the liver to chronic liver injury; when fibrosis progresses to cirrhosis, morbid complications can develop. Available therapies for many chronic liver diseases are ineffective, with liver transplantation as the only option, though the supply of donor organs is inadequate to meet the growing demand. Novel approaches that attack the scarring response are therefore urgently needed. Optimism in this effort is fueled by major insights into the pathogenesis of fibrosis and by accumulating evidence that even cirrhosis is reversible in many patients. Most evolving antifibrotic therapies will be aimed at inhibiting the activated hepatic stellate cell, which is responsible for the fibrotic response to injury. This review describes the ways in which insights into the cellular basis of hepatic fibrosis are leading to realistic strategies for antifibrotic treatment that may revolutionize the management of patients with chronic liver disease.     

Pulmonary vascular innervation and its role in responses to hypoxia: size matters!

The pulmonary vasculature is innervated by specific subsets of sympathetic, parasympathetic, and sensory nerve fibers. In contrast to most other organs, innervation density is highest at large-caliber vessels and decreases toward the periphery, and reactivity to vasoactive compounds also changes along the course. In some species, such as the experimentally widely used rodents rat and mouse, autonomic efferent (sympathetic and parasympathetic) perivascular axons barely reach beyond the lung hilus, whereas in humans this innervation extends to small intrapulmonary vessels. Throughout, the most distal arterioles (i.e., intraacinar arteries equipped with an incomplete coat of intermediate cells instead of a full muscular wall) are devoid of innervation. Altogether, 10 vasoactive substances (3 small molecular transmitters and 7 neuropeptides) at minimum have been identified in various combinations (cotransmission) in pulmonary vascular axons. Analysis of this "neurochemical coding" has been provided only for the guinea pig so far, but not for humans or for animal species commonly used for pulmonary vascular research. Sympathetic pulmonary vascular neurons are reflexively activated via arterial chemoreceptors when arterial Po(2) is lowered and adapt the pulmonary vasculature to this condition of increased pulmonary blood flow by α(1)-adrenoreceptor-mediated increase in vascular impedance primarily at large vessels. In contrast, neither they nor other nerve fibers play a role in the local hypoxic vasoconstriction triggered by low alveolar Po(2), which serves to match perfusion to ventilation. The major potential role of the pulmonary vascular innervation, autonomic and sensory, lies in the pronounced trophic activities of its transmitters.