Architecture and Chemical Coding of the Inner and Outer Submucous Plexus in the Colon of Piglets

In the porcine colon, the submucous plexus is divided into an inner submucous plexus (ISP) on the epithelial side and an outer submucous plexus (OSP) on the circular muscle side. Although both plexuses are probably involved in the regulation of epithelial functions, they might differ in function and neurochemical coding according to their localization. Therefore, we examined expression and co-localization of different neurotransmitters and neuronal markers in both plexuses as well as in neuronal fibres. Immunohistochemical staining was performed on wholemount preparations of ISP and OSP and on cryostat sections. Antibodies against choline acetyltransferase (ChAT), substance P (SP), somatostatin (SOM), neuropeptide Y (NPY), vasoactive intestinal peptide (VIP), neuronal nitric oxide synthase (nNOS) and the pan-neuronal markers Hu C/D and neuron specific enolase (NSE) were used. The ISP contained 1,380 ± 131 ganglia per cm² and 122 ± 12 neurons per ganglion. In contrast, the OSP showed a wider meshwork (215 ± 33 ganglia per cm²) and smaller ganglia (57 ± 3 neurons per ganglion). In the ISP, 42% of all neurons expressed ChAT. About 66% of ChAT-positive neurons co-localized SP. A small number of ISP neurons expressed SOM. Chemical coding in the OSP was more complex. Besides the ChAT/±SP subpopulation (32% of all neurons), a nNOS-immunoreactive population (31%) was detected. Most nitrergic neurons were only immunoreactive for nNOS; 10% co-localized with VIP. A small subpopulation of OSP neurons was immunoreactive for ChAT/nNOS/±VIP. All types of neurotransmitters found in the ISP or OSP were also detected in neuronal fibres within the mucosa. We suppose that the cholinergic population in the ISP is involved in the control of epithelial functions. Regarding neurochemical coding, the OSP shares some similarities with the myenteric plexus. Because of its location and neurochemical characteristics, the OSP may be involved in controlling both the mucosa and circular muscle.

Structure of enteric neurons

The ENS contains numerous different neuron populations which belong to three main groups, primary afferent neurons, interneurons and effector neurons. The most extensive knowledge on the different enteric neuron types is derived from studies in the guinea pig. A significant obstacle for the transfer of this knowledge to putative equivalent enteric neurons of other species, including human, is species differences as to their morphological, chemical, physiological etc. phenotypes. Modern morphological classifications are based on the work of the Russian histologist Dogiel. Since the late 1970s, refined morphological classifications of enteric neurons beyond Dogiel have been attempted mainly in two species, the pig and the guinea pig. These reflect the immunohistochemical diversity of enteric neurons more precisely but are far from being complete. In this paper, we follow two aims. First, we have presented an overview on the chemical coding of the morphological neuron types described by Stach in the pig intestine. In doing so, we have pointed out the difference between the definitions of type I neurons given by Dogiel and Stach. Second, we have attempted to provide a basis for the morpho-chemical classification of human enteric neurons as revealed by their immunoreactivity for NFs and several neuroactive substances or related markers. According to results from guinea pig, where there is functional evidence, human morphological type II neurons (non-dendritic, multiaxonal; co-reactive for NF, CAR, SOM, SP) seem to be the intrinsic primary afferent neurons. This conclusion is based primarily on structural equivalence. Human ENK-positive, stubby (type I) neurons maybe ascending interor motorneurons. In contrast, nitrergic, VIP-reactive spiny (type I) neurons maybe descending inter- or motor neurons. Further, morphologically defined human neuron types, i.e. type III, type V and dendritic type II neurons, are non-nitrergic but could not be chemically defined as yet. Future investigations of morpho-chemical characteristics of human enteric neurons including also other cytoskeletal markers will provide a broader basis for neurohistopathological diagnostics of gut diseases.

Topographic peculiarities of the submucous plexus in the human anorectum--consequences for histopathologic evaluation of rectal biopsies

Chronic colorectal motility disorders are commonly encountered in the pediatric population. While most cases can be managed successfully by conservative therapy, a subgroup of patients suffers from severe constipation and requires further diagnostic procedures to identify the underlying pathologies, such as aganglionosis, hypoganglionosis or intestinal neuronal dysplasia (IND). The present study provides reference data about the quantitative distribution of nerve cells and ganglia within the submucosal plexus of the human anorectum from healthy subjects. Anorectal specimens (n = 15) obtained postmortem were divided into 6 segments beginning from the dentate line (S1 = 0-2 cm, S 2 = 2-4 cm, S3 = 4-6 cm, S4 = 6-8 cm, S5 = 8-10 cm, S6 = 10-12 cm). From each segment sections (6 microm thickness) were immunostained with a pan-neuronal marker (Protein Gene Product 9.5) to visualize the enteric nervous system. A morphometric analysis was carried out for each segment recording the number of ganglia and nerve cells of the submucous plexus. Neither ganglia nor nerve cells showed a uniform distribution pattern, but decreased continuously towards the anus. However, even the lowest segments (S1, S2) contained nerve cells and were not aganglionic. In the remaining segments ganglia with 7 or more nerve cells could be detected. The findings demonstrate segment-specific quantitative differences of the anorectal submucous plexus which should be taken into consideration for the histopathologic evaluation of rectal biopsies. Moreover, the data support the concept of a physiologic hypoganglionosis of the anal canal.

Quantitative morphometric analysis of the submucous plexus in age-related control groups

An increased number and density of the so-called "giant ganglia" (seven or greater ganglion cells per ganglion) serve as histopathological criteria for a bowel motility disorder called intestinal neuronal dysplasia of the submucous plexus (IND B). However, because these morphological criteria have been defined based upon observations in constipated patients, the diagnostic value of previous studies is open to controversy. Moreover, no age-related reference data from unaffected controls are available. This study reports on data from unaffected controls on the variability of size and distribution of ganglia in the submucous plexus during development. Therefore, for the first time, the normal status has been defined. Four age groups have been defined: (a) premature births, gestational age less than 35 weeks; (b) 1-365 days; (c) 1-14 years and (d) 15 years to greater than 70 years). All of these groups revealed giant ganglia in the submucous plexus. With advancing age, there was a decrease in the number of giant ganglia (from 32.7% in group a to 11.2% in group d) accompanied by an inverse increase in the mean distance between all ganglia (from 0.52 mm in group a to 1.17 mm in group d). The data presented permit the conclusion that the criteria mentioned above are not apt to define IND B as an entity, since they do not allow a sufficient demarcation from the age-correlated normal values presented here.

Topography and neurochemistry of the enteric ganglia in the proventriculus of the duck (Anas platyrhynchos)

The topographical distribution of the enteric ganglia has been investigated in the proventriculus of the duck using protein gene product 9.5 (PGP 9.5) immunohistochemistry. Myenteric ganglia were usually located between the outer longitudinal and the inner circular muscle layer. Submucous ganglia were sparsely distributed and seemed to be substituted by ganglia located in the tunica mucosa. The neurochemical profile of proventricular ganglion cells was also investigated using nicotinamide adenine dinucleotide phosphate reduced-diaphorase (NADPH-d)-histochemistry and pituitary adenylate cyclase activating peptide (PACAP)/galanin (Gal) double-labelling immunohistochemistry. The majority of mucosal ganglion cells were shown to contain the NADPH-d enzyme and both the investigated peptides. These findings provide evidence for the presence of a mucosal ganglionated plexus in the glandular stomach of birds. Moreover, the neurochemical characteristics of this plexus suggest that it plays an important role in regulating several mucosal functions and, in particular, the production and the composition of the gastric juice.

Morphometric quantification of normal submucous plexus in the distal rectum of adult healthy volunteers

OBJECTIVE

Inadequate morphometric characterization of the normal adult submucous plexus has precluded the diagnosis of colonic dysganglionoses associated with constipation, such as intestinal neuronal dysplasia type B (IND B). The internal submucous plexus (Meissner plexus) was morphometrically quantified in adult healthy volunteers.

DESIGN

Open, prospective morphometric study in balanced groups of female and male volunteers.

PARTICIPANTS

Thirty-seven adult healthy male and female volunteers with normal bowel function and no history of gastrointestinal disease.

METHODS

Four jumbo rectal biopsies (3-5 mm3) were taken 5 and 10 cm above the pectinate line. Two expert gastrointestinal pathologists assessed biopsy sections after specific nerve cell staining for lactic dehydrogenase, nitric oxide synthase and acetylcholinesterase, mainly for characteristics of ganglia and nerve cells in the submucous plexus.

RESULTS

No healthy individual demonstrated over 20% of submucosal ganglia as giant ganglia or more than four giant ganglia per 30 sections (the morphometric criteria for IND B). Single submucosal nerve cells and ganglion numbers halved between 10 and 5 cm above the pectinate line, but there were no age or gender differences. The biological variability of nerve cell and ganglion density in the submucous plexus was large.

CONCLUSIONS

Healthy adults show less than 20% of submucosal ganglia as giant ganglia and no more than four giant ganglia per 30 rectal biopsy sections. There is therefore no overlap with the histomorphological criteria of IND B. These data therefore support the specificity of the previously defined criteria for IND B in adults.

An immunohistochemical study of the organization of ganglia and nerve fibres in the mucosa of the porcine intestine

In order to elucidate the organization of the enteric nervous system in the mucous plexus, wholemounts from six intestinal regions in six pigs were studied by vasoactive intestinal peptide, substance P, nitric oxide synthase and neurofilament proteins immunohistochemistry. The mucous plexus of both large and small intestine contained ganglia and isolated neurons. They were many and comparably larger in the caecum and colon, few in the ileum, and fewer and smaller in the jejunum. The mucous plexus was subdivided into the lamina muscularis mucosae and lamina proprial subplexuses, and based on location the latter was subdivided further in order to clarify their variations with respect to the amount, sizes and shapes of ganglia and neurons, sizes and orientation of nerve strands and immunoreactivities. Ganglia were situated at different topographical levels in the lamina muscularis mucosae subplexus, outer proprial and interglandular proprial meshworks in the lamina proprial subplexus with the majority of ganglia occurring in the outer proprial meshwork. The mucous plexus in the intestine of the pig is thus a ganglionated plexus showing marked segmental variation in the amount of intramucosal ganglia and isolated nerve cells. These new observations, calls for a re-examination of the mucous plexus to elucidate the regulatory mechanisms of importance in mucosal functions and consideration of the mucous plexus in the intestine of the pig to be one of the major ganglionated plexuses.

The longitudinal smooth muscle layer of the pig small intestine is innervated by both myenteric and submucous neurons

Originally, intestinal motility was thought to be exclusively regulated by myenteric neurons. Some years ago, however, it was demonstrated in large mammals that submucous neurons also participate in the innervation of the circular smooth muscle layer. To date, no information is available about the submucous innervation of the longitudinal smooth muscle layer (LM). This study provides evidence that in the small intestine of large mammals, the LM is innervated not only by the myenteric plexus, but also by the inner and outer submucous plexuses (ISP and OSP). In the porcine small intestine, the involved neurons can be subdivided into the following neurochemically distinct populations: leu-enkephalin (ENK)- and/or substance P (SP)-IR neurons and nitric oxide synthase (NOS)- and/or vasoactive intestinal polypeptide (VIP)-IR neurons. In the myenteric plexus, the majority of VIP- and/or NOS-IR neurons and ENK(+)/SP(-)-IR neurons exhibit descending projections, whereas ENK(+)/SP(+)-IR neurons preferentially have ascending projections. The ENK(-)/SP(+)-IR neurons do not show a polarized pattern. In the OSP, only ENK(+)/SP(-)- and VIP(+)/NOS(-)-IR neurons display a polarized (descending) projection pattern, whereas no polarization can be noted in the ISP. Morphological analysis of the traced neurons revealed that, in general, myenteric descending LM motor neurons have larger cell bodies than ascending ones and, in addition, myenteric descending VIP- and/or NOS-IR neurons have longer projections than ENK and/or SP-IR neurons. In conclusion, the present study demonstrates the involvement of not only myenteric, but also submucous neurons in the innervation of the LM. The two major populations are descending nitrergic neurons and ascending tachykinergic motor neurons, but also other subpopulations with specific projection patterns and neurochemical features have been identified.

Localization and characterization of neuropeptide receptors in human colon

Information about the expression of neuropeptide receptors is limited in human peripheral tissues, such as the gastrointestinal tract, as compared to the brain. A detailed evaluation of binding sites for gastrin-releasing peptide (GRP), neuropeptide Y, vasoactive intestinal peptide (VIP)/pituitary adenylate cyclase-activating polypeptide (PACAP), gastrin/cholecystokinin, neurotensin, substance P and somatostatin was therefore undertaken in human colon using in vitro receptor autoradiography and subtype characterization with receptor-selective ligands. GRP receptors, Y2 receptors, PACAP type1-receptors, cholecystokinin-A receptors, neurotensinl and sst2 receptors were abundantly expressed in the myenteric plexus. Y2, neurotensinl and sst2 receptors were also strongly expressed in the submucosal plexus. Furthermore, expression of GRP receptors, neurokinin (NK)1 receptors, VIP type2-receptors and sst2 receptors was found in the mucosa-directed margin of the circular smooth muscle where the interstitial cells of Cajal are located. A variable and complementary expression of GRP receptors, VIP/PACAP receptors, Y2 neurotensinl, NK1 and somatostatin receptors was found in the circular and longitudinal smooth muscle. NK1 and Y1 receptors were often detected in arteries and veins, while VIP/PACAP and sst2 receptors were found in lymphoid follicles. Y2, VIP type, and sst2 receptors were present in the colonic mucosa. Y2 was strongly expressed in the muscularis mucosae. This study shows that neuropeptide receptors are expressed in high amounts and in highly specific patterns in distinct targets in the human colon, suggesting a major physiological role for these peptides. The data represent the molecular basis to investigate the regulation by neuropeptides of colonic functions and to develop neuropeptide drugs aimed at interacting with these receptors in colonic diseases, such as Hirschsprung's and Crohn's diseases.

The topography, architecture and structure of the enteric nervous system in the jejunum and ileum of cattle

To date, there appear to have been no detailed and clear descriptions of the nerve plexuses and their subdivisions in the intestine of cattle. In this study, the enteric nervous system in the jejunum and ileum of 12 1-y-old calves was examined using neurofilament protein and vasoactive intestinal peptide immunohistochemistry in wholemounts and paraffin sections combined with staining of paraffin and historesin sections with haematoxylin and eosin. The main organisation of the plexuses was similar to that of the pig, horse and man with external and internal submucous plexuses being morphologically distinct, with further subdivisions of the internal submucous plexus into the external and internal subplexuses. However, in contrast to pig, horse and man, the submucous layer was firmly attached to the inner circular muscle layer. The myenteric plexus was well developed with large ganglia, and primary and secondary nerve strands. Its main axis was oriented parallel to the outer longitudinal smooth muscle; large ganglia and primary nerve strands fused to form complex ganglia, and 2 types of tertiary nerve strands were observed. Antibodies to neurofilament proteins and vasoactive intestinal peptide revealed adendritic, pseudouniaxonal or multiaxonal type II neurons only in the myenteric and submucous plexuses. This appears to be the first report of the identification of isolated uniaxonal, multidendritic type IV neurons in the mucous pericryptal plexus. The new information presented here provides further evidence for the existence of anatomical and functional differences between the external and internal submucous plexuses and for supporting the nomenclature proposed earlier.

The organisation of the enteric nervous system in the submucous and mucous layers of the small intestine of the pig studied by VIP and neurofilament protein immunohistochemistry

The arrangement of the enteric ganglia and nerve fibre plexuses was examined in the submucous and mucous layers and around Peyer's patches of the porcine small intestine to clarify their organisation. Immunohistochemistry of vasoactive intestinal peptide (VIP) and neurofilament proteins in wholemounts, chopped or paraffin sections was used to locate the neural elements. The ganglia of the internal and external submucous plexuses were situated at 2 different topographic locations, being clearly demarcated by the submucosal vascular arcades and differing in neuronal composition. The internal submucous plexus was the only contributor to the plexus surrounding the follicles of Peyer's patches as a continuous mesh of 3 ganglionated nerve subplexuses. VIP-immunoreactive fibres from this mesh innervated the dome. The mucosal plexus, which was subdivided into 4 subunits--the outer proprial, inner proprial, pericryptal and villous plexuses--contained a few solitary neuronal perikarya. Labelling for neurofilament proteins revealed Dogiel types II, IV and VI neurons. The observations reveal several new features in the enteric nervous system of the pig and clarify its nomenclature.

In situ visualization of bronchial submucosal glands and their secretory response to acetylcholine

Airway submucosal glands secrete both macromolecules and liquid, yet the mechanisms by which these substances are secreted are not well understood. In this study, a video microscope was used to directly visualize the submucosal glands in isolated porcine distal bronchi and to observe their responses to acetylcholine (ACh), a glandular secretagogue. Submucosal glands were classified as either "antral," "linear," or "convoluted" glands based on the morphology of their terminal collecting ducts. Because antral duct glands were most easily visualized, the response to ACh was studied in detail in this gland type. Within 5-10 s after addition of 10 microM ACh, the cross-sectional area of the gland duct openings to the airway surface increased severalfold but returned to pre-ACh dimensions within 1 min. Between 30 s and 10 min after ACh addition, spherical particles (1-10 microm) entered the antral ducts from distal acini and exited through the duct openings to the airway surface. Some of the particles were retained within the antral duct where they were kept in constant motion by the action of cilia present within the antral duct. The particles, which are likely to contain the macromolecular secretory products of mucous and/or serous cells, maintained their spherical shape within the gland duct, suggesting that the secretion product was membrane bound. To our knowledge, these studies provide the first description of airway submucosal gland secretion as viewed in situ.

The inner sublayer of the circular muscle coat in the canine proximal colon: origins of spontaneous electrical and mechanical activity

In the canine proximal colon, tissue near the submucosal surface of the circular muscle layer produces spontaneous mechanical contractions, synchronized with electrical slow waves. Comparative physiological examination of tissue strips from various regions of the submucosa and circular muscle coat revealed that the characteristic smooth muscle tissue of the innermost sublayer of the circular muscle is required for this rhythmical phenomenon. Histological examination showed that tissues containing special smooth muscle cells form an inner sublayer of the circular muscle coat. These innermost muscle cells were distinguishable from the bulk circular muscle cells by the following features: 1) flattened and shorter shapes of the cell and nucleus, 2) numerous caveolae on the cell surface, 3) abundant mitochondria, and 4) frequent gap-junction formations. Neither slow waves nor spontaneous mechanical rhythmicities were recorded from the submucosal connective tissue or from the bulk circular muscle tissue without the inner sublayer. The thicker smooth muscle cells found in the submucosal border specimens were identical in histological features to the bulk circular muscles which produced no slow waves and no spontaneous contractions. Cellular elements in the interstitium, such as fibroblasts, mast cells and macrophages, were found in all tissue strips that were physiologically examined. Nerve elements were found in all the specimens; however, there was a unique nerve network probably corresponding to the plexus entericus (submucosus) extremus described by Stach (1972). It was concluded, therefore, that the inner sublayer characterized by special smooth muscle cells with a delicate nerve plexus is essential for producing spontaneous activities of the circular muscle coat in the canine proximal colon.

Calcitonin gene-related peptide-containing neurons supplying the rat digestive system: differential distribution and expression pattern

In the enteric nervous system, calcitonin gene-related peptide (CGRP) immunoreactivity is localized to a substantial number of capsaicin-sensitive afferent fibers and to intrinsic neurons and processes. CGRP immunoreactivity detected by immunohistochemistry represents the expression of two distinct genes, the calcitonin/alpha-CGRP and the beta-CGRP genes, which have different tissue distributions. In the present study, we used (1) in situ hybridization histochemistry and ribonucleic acid (RNA) blot hybridization with RNA probes complementary to the divergent sequences of alpha- and beta-CGRP messenger RNAs (mRNAs) to differentiate which CGRP gene was expressed in enteric and afferent neurons; and (2) axonal transport approaches in combination with CGRP immunohistochemistry to define the location of CGRP-containing afferent neurons supplying the digestive system. In situ hybridization histochemistry with [35S]-labeled RNA probes indicated that in the gastrointestinal tract beta-CGRP mRNA, but not alpha-CGRP mRNA, was expressed in enteric neurons confined to the myenteric and submucous plexuses of the small and large intestine. In dorsal root and vagal sensory ganglia, mRNAs for alpha-CGRP and beta-CGRP were both present in a vast population of neurons, with an overlapping pattern, even though the alpha-CGRP signal appeared more intense. RNA blot hybridization analysis showed a single band of hybridization at 1.2 Kb with the beta-CGRP RNA probe in RNA extracts from muscle layer-myenteric plexus and submucosal layer preparations of the ileum, and from dorsal root ganglia; it also showed a single band at 1.3 Kb with the alpha-CGRP RNA probe in extracts from dorsal root ganglia, but not from the intestine. These findings further support the differential expression of alpha- and beta-CGRP mRNAs. Retrograde transport of fast blue or fluorogold coupled with CGRP immunohistochemistry demonstrated that the vast majority of CGRP-containing afferent neurons supplying the stomach, proximal duodenum, and pancreas were located in dorsal root ganglia at the middle and lower thoracic and at the upper lumbar levels, and represented a major component of the afferent innervation of these viscera (up to 89%). Approximately 50% of CGRP-immunoreactive afferent neurons also expressed tachykinin (TK) immunoreactivity, as shown by triple labeling. Only a minor component of the afferent innervation of the stomach, duodenum, and pancreas derived from vagal CGRP-containing neurons (less than 8%). A large portion of these neurons (an average of 62%) also contained TK immunoreactivity.(ABSTRACT TRUNCATED AT 400 WORDS)

An in vitro study of the projections of enteric vasoactive intestinal polypeptide-immunoreactive neurons in the human colon

The anatomical basis of the peptidergic neural control of the human colon is largely unknown. In this study, in vitro retrograde tracing methods have been used on fresh human colon to determine the projection pathways of the enteric nerves and, in particular, those containing vasoactive intestinal polypeptide, one of the most abundant and potent of the gut neuropeptides. Two components of the submucous plexus were identified, the inner one projecting to the lamina propria, and the outer to the circular muscle. The lengths of projections within the submucous plexus were up to 5-14 mm in all directions. Myenteric ganglion cells projected to both longitudinal and circular muscles, for distances of up to only 5 mm. The subpopulation of nerves containing vasoactive intestinal polypeptide arose mainly from the submucous plexus and projected up to 6.5 mm anally, 5 mm orally, and 14 mm within the submucous layer to the mucosa or circular muscle. These findings provide entirely new data on the neuroanatomy of the human colon and may help in the understanding of the neural control of colonic secretion and motility.

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)

Intrinsic nerves in the mammalian colon: confirmation of a plexus at the circular muscle-submucosal interface

Slow waves in the small intestine seem to arise in plexuses of neurites with interstitial cells of Cajal. In the colon, slow waves appear to arise at the circular muscle - submucosal interface. We therefore sought a plexus at this surface in the colon in the cat, dog, ferret, opossum, rabbit, rat, guinea-pig and man. Segments from all levels of the colon were stained by the Champy-Maillet osmic acid-zinc iodide method and cut into serial 25 micron sections in the plane of the muscle layers. A dense network of neurites with abundant interstitial cells of Cajal was found at the circular muscle - submucosal interface in all species except rabbit. Neurites in this plexus appeared to arise from the deep plexus of the submucosa (Schabadasch's or Henle's plexus). It was not found in the small intestine and stomach. A similar plexus was found in the interstices of the myenteric plexus in the colon. Interstitial cells of Cajal in both plexuses were positive for the NADH-diaphorase stain, but not for silver impregnation. The possible roles of the plexuses of neurites and interstitial cells of Cajal at the circular muscle - submucosal interface and at the plane of the myenteric plexus in the generation of rhythmic activity in the colon are discussed.

[The hypoganglionic and aganglionic high pressure zone of the anterior esophagus (the esophageal opening) and its special blood supply (angiomuscular sphincter closure]

At the mouth of the oesophagus there is an aganglionic zone similar to that in the anorectal organ of continence. This is part of the system of permanent closure. Since the musculature at the oesophageal entrance is arranged in a screw-like fashion the aganglionic zone lies obliquely to the longitudinal axis of the oesophagus. Closure at the oesophageal entrance is further supported by a kind of corpus cavernosum similar to that in the rectum. In this pharyngeal corpus cavernosum blood is drained between the muscular fibres and their contraction prevents its drainage, thus facilitating the closure of the musculature. The constrictor pharyngeus muscle takes a similar course as does the puborectalis which leads to a bend in the anal canal. Thus also at the entrance to the gastrointestinal tract an arterial angiomuscular system of closure exists in the center of which an aganglionic segment is conspicuous.

Submucosal plexus and electrolyte transport across rat colonic mucosa

Electrolyte transport across two preparations of mucosa from rat colon descendens was compared to determine what influence the submucosal plexus has on electrolyte transport. One preparation consisted of the mucosa, muscularis mucosae, and the submucosal tissue and is referred to as the mucosa-submucosa preparation. The second preparation obtained by further blunt dissection of the mucosa-submucosa preparation consisted of only the mucosa and the circular muscle layer of muscularis mucosae and is referred to as the mucosa preparation. Histological studies showed that the submucosal tissue and the longitudinal layer of muscularis mucosae could be removed leaving only the mucosa and the circular layer of muscularis mucosae. The extensive neuronal network of the submucosa was shown when the submucosal tissue and longitudinal muscle layer of muscularis mucosae, which were removed, were stained histochemically for acetylcholinesterase activity. Both the mucosa-submucosa and mucosa preparations absorbed Na+ and Cl- when short-circuited. However, Na+ and Cl- absorption were significantly higher in the mucosa preparation. The increase in Na+ and Cl- transport in the mucosa preparation was accompanied with a decrease in the short-circuit current (Isc), the open-circuit potential difference (p.d.) and the transmural tissue conductance (Gt) when compared to the mucosa-submucosa preparation. Tetrodotoxin (TTX), a neurotoxin which blocks specifically the propagation of action potentials in excitable tissues, dose-dependently decreased Isc and p.d. in the mucosa-submucosa preparation when added to the serosal solution. The half-maximal effective concentration of TTX was 5 nM and maximal effective concentration 100 nM. TTX (1 microM) had no effect on Isc or p.d. when added to the mucosal solution. The decrease in Isc and p.d. caused by TTX in the mucosa-submucosa preparation was accompanied with an increase in Na+ and Cl- absorption. TTX caused only a small decrease in Isc and p.d. in the mucosa preparation. However, there was no measurable change in Na+ and Cl- transport in the mucosa preparation. The results suggest that spontaneously active neurones from the submucosal plexus have an inhibitory influence on the mucosa. Physical removal of the submucosal plexus or pharmacological blockade of the neurones within the mucosa-submucosa preparation by TTX led to enhanced absorption, suggesting that the set point of the mucosa for electrolyte transport is at or near a maximal absorptive state. Regulation or modulation of the mucosa may therefore occur by mechanisms that lower this set point, causing an inhibition of absorption of electrolytes.

Fluorescence microscopic study of the architecture and structure of an adrenergic network in the plexus myentericus (Auerbach), plexus submucosus externus (Schabadasch) and plexus submucosus internus (Meissner) of the porcine small intestine

The distribution of adrenergic fibres in the ganglionated plexuses of the porcine small intestine has been made on air-dried stretch preparations using the glyoxylic acid fluorescence method. Adrenergic fluorescent fibres occur in the ganglia and internodal strands of the three fundamental ganglionated plexuses: the myenteric plexus (Auerbach) and the two superimposed meshworks of the plexus submucosus , i.e. the plexus submucosus externus ( Schabadasch ) and the plexus submucosus internus (Meissner). The plexus Auerbach consists of densely glyoxylic acid induced fluorescent (GIF) elongated ganglia with in general a longitudinal axis running parallel to the circular muscle layer and large dense interconnecting fibre tracts with primary, secondary and tertiary subdivisions. In the ganglia, the fibres are varicose, forming large fluorescent 'baskets' which might be related to the occurrence of well defined enteric neurones. The plexus Schabadasch can be distinguished from the plexus Meissner by its size, strongly fluorescent ganglia and broad densely fluorescent internodal strands. The pattern of fluorescing ring-like formations at the margin and out of the nodes, clearly present in the Auerbach and Schabadasch plexuses, completely lack in the plexus Meissner, the latter being narrow-meshed with smaller fluorescent 'baskets', indicating that the corresponding neurones are smaller in size. In the ganglionic nodes of all three plexuses the axons display comparatively more varicosities than in the fibre tracts. Each of the three main ganglionated enteric plexuses are quite different with regard to the pattern of the adrenergic network both in the ganglia and in the strands.

Neurones localized with antibodies against choline acetyltransferase in the enteric nervous system

This is the first report of the histochemical localization of peripheral neurones with antibodies raised against choline acetyltransferase. The antiserum was raised in a rat against the enzyme purified from porcine brain. An indirect immunohistochemical technique was used to localize nerve cell bodies and nerve fibres in the stomach, small intestine and colon of the guinea-pig and the mouse small intestine. Reactive nerve cell bodies were found in both the myenteric and submucous ganglia. Varicose nerve fibres were in the ganglia, in the circular smooth muscle and in the mucosa of the small intestine.

Further histophysiological observations on the lower esophagus of the rabbit

Previous neurohistological studies have been extended to include the structures contained solely or mainly within the junctional esophageal segment which may play an important role in the sphincter mechanism. The main findings were: 1) a progressive cranio-caudal thickening of the muscularis mucosae; 2) a conspicuous thickening of the circular muscle layer; 3) abundant and close interconnections between the esophageal striated fibres and gastric smooth muscle cells; 4) presence of annulo-spiral elastic fibres coiled around bundles of striated musculature; 5) increase of the intramural nerve component, particularly Auerbach's plexus, which consisted of a continuous nervous layer containing twice as many neurocytes as found in the upper esophageal segments; 6) presence of numerous interconnected motor endplates often possessing ultraexpansional fibres and secondary endplates. The findings are discussed with emphasis on functional correlations in order to attain a unitary morpho-functional view.

Acetylcholinesterase-positive nerves of the rhesus monkey bronchial tree

The rhesus monkey lung was stained both by histological methods and histochemically for specific acetylcholinesterase (AChE). AChE-containing nerves in bundles were demonstrated in connective tissue of the hilum and in association with clusters of ganglion cells. These bundles become associated with the bronchial tree as they enter the lung parenchyma, and their numbers of myelinated fibres diminish as they pass scattered ganglion cells along the bronchial system. Extrachondral and subchondral plexuses of nerves were found to be interconnected and to contribute to the perimuscular varicose nerve plexus of the bronchi and bronchioles. These nerve plexuses were found to extend as far as the respiratory bronchioles. In the bronchial submucosa there are AChE-positive nerve plexuses which arise from three sources: (1) the adventitial plexus in bronchioles, or the subchondral plexus in bronchi, (2) the perimuscular nerve plexus, and (3) AChe-containing nerves associated with the bronchial artery. The submucosal plexus appears to innervate the acinar submucosal glands in bronchi as well as continuing as central nerves in the mucosal folds. In the bronchioles the nerves in the mucosal fold are in close relationship with the mucosa.

Observations on the submucous plexus and mucosal arteries of the dog's stomach and first part of the duodenum

Arteriolar patterns of the submucous plexus were studied in all areas of the dog's stomach and in the first inch of the duodenum. There appeared to be no poverty of plexus, although in some cases the vessels were somewhat smaller in the pyloric part of the lesser curvature than elsewhere. Mucosal arteries arose from the plexus, and none appeared to have an extramural origin. In man, on the other hand, there is a poverty of the submucous plexus in the 'ulcer region', i.e. in the incisural region of the lesser curvature and in the first inch of the duodenum, associated in some cases with mucosal end arteries of extramural origin. The absence of these features in the dog, which does not suffer from spontaneous chronic ulceration, lends further support to the view that they play a role in the aetiology of the disease in man.

Sensory nerves in the mammalian urinary tract. An evaluation using light and electron microscopy

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Histological and histochemical observations on the myenteric and submucous plexuses of mammals

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