Human myenteric plexus: confirmation of unfamiliar structures in adults and neonates

To define the myenteric plexus along the human gastrointestinal tract, we studied three neonatal and six adult specimens, postmortem, by silver impregnation. There were no clear differences between the neonatal and the adult gastrointestinal tracts. In the body of the esophagus, the plexus was sparse, with few ganglia; 30%-40% of fascicular intersections were devoid of ganglia. In the lower 5 cm, the esophagus had thick bundles of nerve fibers ("shunt fascicles"), which crossed the gastroesophageal junction and radiated to the periphery of the stomach through several branches. The plexus in the stomach was uniform, with intermediate and intrafascicular ganglia. A thick nerve bundle encircled the pylorus and gave branches on either side to the antrum and the duodenum. Shunt fascicles in the stomach did not cross the pylorus but extended to the distal antrum. In the duodenum and proximal jejunum, the plexus was regular, but in the mid-small intestine, the longitudinal interganglionic fascicles were more prominent than the circumferential fascicles. Distally, this pattern was reversed; circumferential fascicles were more prominent and ganglia were dense in the terminal ileum. Thin, short shunt fascicles were scattered along the entire small intestine, becoming more abundant in the terminal ileum. Short, thick shunt fascicles traveled proximally from the ileocecal junction for about 25-30 cm. As in the stomach, shunt fascicles did not cross the ileocecal junction, but a thick nerve bundle encircled it. In the cecum and proximal colon, the plexus was sparse with large intermediate and intrafascicular ganglia. In the rectum and distal colon, the plexus was dense, with parafascicular and intrafascicular ganglia. Long ascending nerves extended from the distal rectum into the midcolon. In addition, there were short, thick nerve bundles in the rectum that traveled proximally.     

Nerve cell density in submucous plexus throughout the gut of cat and opossum

Quantitative differences in submucous plexus density were sought in cat and opossum gut by examining full-thickness whole mounts of the submucosa stained with silver, and counting ganglia per square centimeter and nerve cell bodies per ganglion in order to compute density of innervation (nerve cell bodies per square centimeter). In the cat, the nerve cell bodies per square centimeter in the 12 named regions were as follows: proximal esophagus, 0; mid-esophagus, 0; distal esophagus, 0; fundus, 84; gastric antrum, 18; duodenum, 5831; jejunum, 4632; ileum, 3191; proximal colon, 1275; mid-colon, 689; distal colon, 359; rectum, 144. In the opossum, values were as follows: proximal esophagus, 37; mid-esophagus, 52; distal esophagus, 84; duodenum, 1812; jejunum, 2234; ileum, 1488; proximal colon, 206; mid-colon, 197; distal colon, 121; rectum, 61. Adequate specimens could not be obtained from opossum stomach. Differences were due more to variations in distribution density of ganglia than in ganglionic size. The relatively dense submucous plexus of the intestine probably is related to the capacity of the intestinal mucosa for peptide secretion as well as to its absorptive function.     

Increased smooth muscle contractility of intestine in the genetic null of the endothelin ETB receptor: a rat model for long segment Hirschsprung's disease

BACKGROUND AND AIMS: The endothelin ETB receptor null rat (ETB(-/-)R) has an intestinal segment without ganglia, and this rat is characterised by intestinal obstruction similar to that observed in human Hirschsprung's disease. In the present study, we have examined the myogenic mechanism responsible for obstruction in the ETB(-/-)R. RESULTS: The ETB(-/-)R had an enlarged belly and the average lifespan was 18.1 days. The bowel from the rectum to the lower part of the small ileum was constricted whereas the upper region was dilated with faecal stasis and thus presented as megaileum. The constricted muscle segments without ganglia had a greater increase in absolute force when stimulated by carbachol, high K+, and endothelin-1 compared with that of normal siblings. In contrast, in the dilated part with ganglia, the absolute contractile force due to these stimulants in the ETB(-/-)R was not different from that in the ETB(+/+)R. Such a functional hypertrophy of the musculature was observed in parts of the colon, caecum, and distal ileum without ganglia but not in the part of the proximal ileum and jejunum with ganglia. Morphological study demonstrated that the thickness of the circular and longitudinal muscle layers was greater in the constricted part of the intestine in the ETB(-/-)R, and these changes were associated with an increase in the number of smooth muscle cells. CONCLUSIONS: Our findings suggest that both increased contractility of smooth muscle and increased thickness of the intestinal muscular wall may contribute to the intestinal obstruction in the ETB(-/-)R.     

Enteric nerves in diabetic rats: increase in vasoactive intestinal polypeptide but not substance P

The distribution of vasoactive intestinal polypeptide (VIP) and substance P-like immunoreactivities was studied by immunohistochemistry in the myenteric plexus and circular muscle layer of the ileum and proximal colon of rats 8 wk after induction of diabetes with streptozotocin. A consistent increase was observed in fluorescence intensity of VIP-like immunoreactivity in the nerve fibers, and intensely stained cell bodies were significantly more frequent in the myenteric plexus of the ileum (p less than 0.001) from diabetic animals. Some varicosities of VIP-like immunoreactive fibers in the myenteric plexus appeared to be enlarged. Vasoactive intestinal polypeptide-like immunoreactivity was increased and VIP-like immunoreactive nerves appeared thicker in the circular muscle layer of both diabetic ileum and proximal colon. The VIP levels were measured biochemically in tissue consisting of the smooth muscle layers and myenteric plexus. A significant increase in the VIP content per centimeter of intestine was found in both the ileum (p less than and proximal colon (p less than 0.01) from diabetic rats. In contrast, no apparent change in substance P innervation was observed immunohistochemically in the myenteric plexus and circular muscle layer of either diabetic ileum or proximal colon when compared with controls. The results are discussed in relation to the symptoms of autonomic neuropathy of the gut in diabetes.     

Region-specific differences in the human myenteric plexus: an immunohistochemical study using donated elderly cadavers

Purpose and methods

To identify site-dependent and individual differences in neuronal nitric oxide synthase (nNOS)-positive nerves of the myenteric plexus, we examined full-thickness walls of the stomach, pylorus, duodenum, ileum, colon, and rectum in 7 male and 8 female cadavers (mean ages, 80 and 87 years, respectively).

Results

The areas occupied by nNOS-positive nerve fibers in the myenteric plexus were fragmentary and overlapped with areas occupied by vasoactive intestinal polypeptide-positive fibers. The nNOS-positive fiber-containing areas per 1-mm length of intermuscular space tended to be larger at more anal sites, with positive areas four times greater in the rectum than in the stomach. Interindividual differences in rectal areas were extremely large, ranging from 0.017 mm² in one 80-year-old man to 0.067 mm² in another 80-year-old man. Similarly, the numbers of nNOS-positive ganglion cell bodies per 1-mm length in the rectum ranged from 4 to 28. These areas and numbers were weakly correlated (r?=?0.62; p?=?0.02). Interindividual differences in the rectum appeared not to depend on either age or gender.

Conclusions

Anatomic studies using donated cadavers carried the advantage of obtaining any parts of intestine within an individual, in contrast to surgically removed specimens. We speculated excess control of evacuation with laxatives as one of causes of atrophy of the rectal myenteric plexus.     

Differential effect of streptozotocin-induced diabetes on the innervation of the ileum and distal colon

The effect of short-term and long-term streptozotocin-induced diabetes on the pattern of distribution and tissue content of adrenergic and peptidergic nerves in ileum and distal (descending) colon of the rat was examined using immunohistochemical, biochemical, and immunochemical techniques. The effect of short-term streptozotocin-induced diabetes on the level of noradrenaline compared with weight-restricted (starved) and untreated controls in the celiac (celiac-superior mesenteric ganglia complex) and inferior mesenteric ganglia, which supply the two regions of the intestine, was also compared. The pattern of change in the distribution of dopamine-beta-hydroxylase-, substance P-, calcitonin gene-related peptide-, and vasoactive intestinal polypeptide-like immunoreactive nerve fibres that was observed in the ileum from diabetic rats was not evident in the myenteric plexus of distal colon. In contrast to the ileum, there was no evidence of degenerative change in any of the nerve types investigated in the myenteric plexus of the distal colon. The level of vasoactive intestinal polypeptide in the diabetic rat ileum was significantly increased, whereas the level of noradrenaline was reduced; no such changes were observed in the distal colon. The tissue content of noradrenaline in the celiac ganglion, which projects to the ileum, was increased at 8-week diabetes compared with both weight-restricted and untreated controls, whereas the diabetic state had no effect on the levels of noradrenaline of the inferior mesenteric ganglion, which projects to the distal colon. It is concluded that there is a differential effect of streptozotocin-diabetes on different regions of the rat intestine. The adrenergic and peptidergic innervation of the distal colon were changed little compared with ileum. This may be explainable in terms of the different functional roles of these two regions of the intestine and/or by the difference in origin of the sympathetic nerves supplying the two regions of the intestine.     

Enteric neuronal plasticity and a reduced number of interstitial cells of Cajal in hypertrophic rat ileum

Department of Physiology and Neuroscience, University of Lund, Sweden

Correspondence to: Dr E Ekblad, Department of Physiology and Neuroscience, Section of Neuroendocrine Cell Biology, University of Lund, Lund University Hospital, E-blocket vån 5, S-221 85 Lund, Sweden.

Accepted for publication 19 January 1998

Background—Partial obstruction of the ileum causes a notable hypertrophy of smooth muscle cells and enteric neurones in the proximally located intestine.
Aims—To study the expression of neuromessengers in the hypertrophic ileum of rat as little is known about neuromessenger plasticity under these conditions. To investigate the presence of interstitial cells of Cajal (ICC) in hypertrophic ileum.
Methods—Ileal hypertrophy was induced by circumferential application of a strip of plastic film for 18-24 days. Immunocytochemistry, in situ hybridisation, nicotinamide adenine dinucleotide phosphate (NADPH) diaphorase histochemistry, and ethidium bromide staining were used to investigate the number of enteric neurones expressing neuropeptides and nitric oxide synthase, and the frequency of ICC.
Results—In the hypertrophic ileum several neuronal populations showed changes in their expression of neuromessengers. Myenteric neurones expressing vasoactive intestinal peptide (VIP), pituitary adenylate cyclase activating peptide, and galanin were notably increased in number. In submucous ganglia the number of VIP immunoreactive neurones decreased while those expressing VIP mRNA increased. NADPH diaphorase positive submucous neurones increased dramatically while the number of neuronal type nitric oxide synthase expressing ones was unchanged. The number of ICC decreased notably in hypertrophic ileum.
Conclusion—Enteric neurones change their levels of expression of neuromessengers in hypertrophic ileum. ICC are also affected. The changes are presumably part of an adaptive response to the increased work load.
(GUT 1998;:836-844)

Keywords: enteric nerves;  interstitial cells of Cajal;  hypertrophy;  neuropeptides;  nitric oxide;  neuronal plasticity

     

Neurochemical coding in the small intestine of patients with Crohn''s disease.

BACKGROUND: There have been conflicting results regarding the effect of Crohn's disease on the neurochemical composition of the enteric nervous system. AIMS: To examine the effect of Crohn's disease on the neurochemical composition of enteric nerve fibres and cell bodies using whole mount preparations of human ileum. METHODS: Whole wall ileum from seven normal subjects and nine patients with Crohn's disease was used to investigate the neurochemical composition of neurones and nerve fibres in the myenteric plexus, circular muscle, and serosa layer of ileum using immunohistochemical techniques. RESULTS: Increased tyrosine hydroxylase, 5-hydroxytryptamine, and neuropeptide Y immunoreactivity was exclusively seen in the myenteric plexus. There was increased neurofilament immunoreactivity in the myenteric plexus and nerve fibres of the circular muscle layer, and thick bundles of immunoreactive nerve fibres in the serosa layer. Increased vasoactive intestinal polypeptide, nitric oxide synthase, and pituitary adenylate cyclase activating peptide immunoreactivity was seen in the myenteric plexus and nerve fibres of the circular muscle layer, and aggregates of inflammatory cells in the serosa layer of the afflicted segment of Crohn's ileum. In addition, there was a chaotic display of nerve fibres containing some of the neuroactive substances with a high frequency of enlarged varicosities in the myenteric ganglia and/or nerve fibres of the circular muscle layer of Crohn's ileum. CONCLUSION: Results show quantitative as well as qualitative changes in the neurochemical composition of enteric nerve fibres and nerve cell bodies of Crohn's ileum. These changes and the presence of nitric oxide synthase and peptides immunoreactive inflammatory cells in the serosa layer suggest that nerve-immune interactions may have a significant role in the process of the inflammatory changes seen in Crohn's ileitis.     

Selective damage of intrinsic calcitonin gene-related peptide-like immunoreactive enteric nerve fibers in streptozotocin-induced diabetic rats

The distribution of calcitonin gene-related peptidelike immunoreactive (CGRP-LI) nerve fibers in the myenteric plexus of ileum and proximal colon of rats 8 wk after induction of diabetes with streptozotocin was studied using immunohistochemical techniques. A marked decrease in CGRP-LI nerve fibers mainly around the ganglion cells of the myenteric plexus of both ileum and proximal colon was observed in diabetic rats. The sparsely located immunoreactive nerve cell bodies in the control rats were absent in the diabetic preparations. There were, however, intensely stained CGRP-LI varicose nerve fibers that ran through the internodal strands and over the myenteric ganglia of the diabetic intestines. These findings indicate the presence of CGRP-LI nerve fibers of dual origin in the intestinal wall. The absence of positive cell bodies and diminished CGRP-LI nerve fibers around the ganglion cells in the diabetic tissues suggest that the state of diabetes selectively affects CGRP-LI nerve fibers of intrinsic rather than extrinsic origin. Furthermore, the absence of change in substance P-like immunoreactivity in the enteric system of rats with streptozotocin-induced diabetes of the same duration suggests that calcitonin gene-related peptide and substance P are contained in different populations of intrinsic nerve fibers in the gastrointestinal tract of the rat.     

An Unusual Form of Aphthoid Proctocolitis

Abstract: An unusual form of aphthoid colitis is presented. A 21 -year-old man complained of hematochezia for about 2 years. Examinations revealed crowded polypoid lesions in the lower rectum: the closer to the anus the site was, the bigger the size of the polypoid lesions. Polypoid lesions were also observed in the terminal ileum and on the ileocecal valve. Biopsy specimens revealed that these polypoid lesions were lymph follicles. Lymphoid hyperplasia was observed in the upper rectum and proximal colon but not in the transverse colon. The patient was given a salicylazosulfapyridine suppository followed by a rapid ceasing of hematochezia on the following day and disappearance of most lymph noduli in the rectum by the second week. About two years later hematochezia recurred. The findings of the lower rectum and the response to the suppository were the same as in the first episode. Known diseases associated with aphthoid colitis were ruled out. The present case is unusual in several respects compared to typical apthoid colitis: the clinical course is not acute self-limited but chronic protracted; the lesions are distributed not evenly in the large bowel or its segment(s) but in the lower rectum, in addition, the lesions become more pronounced toward the anus; skipped lymph noduli are observed in the ileocecal valve and the terminal ileum. The other characteristics of this case include a marked response to salicylazosulfapyridine, recurrence, no precedence of flu-like syndromes, no symptoms except for hematochezia, and normal laboratory data.     

Comparative anatomy of the myenteric plexus of the distal colon in eight mammals

The behavior of the most distal part of the colon in a variety of species suggests that the innervation of this part may differ from that of more proximal parts. Silver impregnation was used to demonstrate the arrangement of the myenteric plexus of the distal colon in eight species (rat, guinea pig, rabbit, Australian possum, American opossum, cat, dog, and monkey). A distal zone, approximately 5%-20% of the total length of the colon above the anal verge in the nonrodents, was characterized by a plexus of very irregularly disposed intersecting nerve bundles of highly variable size with few and small ganglia; this zone was absent in the three rodent species. A next most distal zone, approximately 10%-65% of the total colonic length, contained a stellate plexus of large, regularly disposed ganglia interconnected by small nerve fiber bundles upon which were superimposed large dark-staining nerve bundles; these bundles began to be seen at the level of the irregular rectal plexus and ran cephalad, bypassing some ganglia but giving off branches to others. These, called shunt fascicles, contained many myelinated nerve fibers. Above this zone, the plexus was a stellate plexus throughout the remainder of the colon.     

Electron microscopy of myenteric nerves in Hirschsprung''s disease and in normal bowel

The ultrastructure of the myenteric nerves of colon and rectum removed from 10 children with Hirschsprung's disease has been studied and compared with normal infant bowel.Distal aganglionic (Hirschsprung) bowel often showed a rich supply of nerves within the muscle layers and there was no obvious morphological abnormality of constituent axons. The numbers of nerves diminished as more proximal parts of the bowel were examined and the fewest nerves were found where ganglia first appeared. These ganglia were similar in structure to the ganglia of normal bowel, and a striking feature of them all was the absence of collagen between constituent neuronal units. The larger nerve trunks of aganglionic bowel frequently contained myelinated axons and these have been observed within the myenteric plexus of normal rectum.This study supports previous histochemical investigations of the nerves in bowel from patients with Hirschsprung's disease and indicates that the condition is due to a complex and variable abnormality of the arrangement of the nervous tissue of the bowel wall, involving myenteric nerves as well as ganglia.     

Substance P-containing nerve fibers are numerous in human but not in feline intestinal mucosa

The regional and topographic distribution of substance P-containing nerve fibers in the human and feline intestinal wall was studied by immunocytochemistry and radioimmunoassay. The concentration of substance P was measured in the different layers of the duodenum, jejunum, ileum, and colon. In both humans and cat, substance P fibers were fairly numerous, and the substance P concentration was comparatively high in the smooth muscle layer, including the myenteric ganglia. In humans, but not in cat, substance P fibers were numerous, and the substance P concentration was also high in the mucosa. Substance P-containing nerve cell bodies were observed in the myenteric ganglia of both species. In the submucous ganglia, such nerve cell bodies were seen in the human intestine only, suggesting that they represent the origin of the numerous mucosal substance P fibers in this species. Previous studies have revealed a relative paucity of substance P fibers in the intestinal mucosa of several mammals, such as mouse, rat, and pig. The cat can now be added to those having few mucosal substance P fibers, whereas humans seem to be notably rich in such fibers, suggesting that substance P may play a role in the regulation of mucosal functions in the human intestine.     

Colorectal Motility Induction by Sacral Nerve Electrostimulation in a Canine Model

PURPOSE: This study investigated the role of the sacral nerves in the mechanism of defecation using adult mongrel dogs. The possibility of designing a colonic pacemaker as a new therapeutic device to treat defecation disturbances, such as fecal incontinence and severe constipation, is also discussed. METHODS: Colorectal motility during spontaneous defecation was monitored with force strain-gauge transducers implanted in the proximal, distal, and sigmoid colon, rectum, and internal anal sphincter. Under general anesthesia, the sacral nerve was stimulated electrically, and the colorectal motility response was examined. RESULTS: During spontaneous defecation, three characteristic motility patterns were observed: 1) giant migrating contractions of the colon were propagated to the rectum or anus; 2) the rectum relaxed before the giant migrating contractions were propagated; and 3) the internal anal sphincter was relaxed during the propagation of the giant migrating contraction. Sacral nerve stimulation elicited the following three unique responses: 1) contractile movements were propagated from the distal colon to the rectum; 2) a relaxation response was noted in the rectum; and 3) the internal anal sphincter exhibited a relaxation response. The duration and propagation velocity of the contractile responses and the duration of relaxation responses elicited by electrical stimulation of the sacral nerve were similar to those that occurred during spontaneous defecation, but their amplitudes were smaller. CONCLUSION: The coordinated processes of the colon and anorectum during defecation were affected by the sacral nerves. This suggests that it is possible to design a colonic pacemaker to control lower colonic and rectal movements.     

Distribution and Colocalization of Nitric Oxide Synthase and Calretinin in Myenteric Neurons of Developing, Aging, and Crohn's Disease Human Small Intestine

The pattern of distribution and colocalizationof nitric oxide synthase and the calcium-binding proteincalretinin in myenteric neurons and nerve fibers wereexamined in the human small intestine from preterm fetuses (14-17 weeks of gestation), normaladults (mean age 50 years old), old age (mean age 80years old), and Crohn's disease patients (mean age 30years old) using NADPH-diaphorase histochemistry and immunohistochemical techniques. In all agegroups investigated, NADPH-diaphorase-reactive andcalretinin-immunoreactive neurons and nerve fibers wereseen throughout the myenteric plexus. The highestproportion of NADPH-diaphorase-reactive neurons was foundin the myenteric ganglia of old age intestines (56% ofprotein gene product-immunoreactive neurons) followed byfetal intestines (41%) and Crohn's intestine (30%) compared with intestines of controladults (20%). A similar trend was observed forcalretinin-immunoreactive neurons where the highestproportion of immunoreactive neurons was found in themyenteric ganglia of old age intestines (28% of proteingene product-immunoreactive neurons), followed by fetalintestines (22%), and Crohn's intestines (18%) comparedwith intestines of control adults (9%). A colocalization of NADPH-diaphorase activity and calretininimmunoreactivity was only seen in the myenteric neuronsof fetal intestines (2% of NADPH-diaphorase-reactiveneurons were also calretinin-immunoreactive). The pattern of distribution of NADPH-reactive andcalretinin-immunoreactive neurons in the myentericganglia of fetal intestine differs from that of theother age groups. In the fetal intestine, the myenteric neurons containing either calretinin orNADPH-diaphorase are distributed through out themyenteric ganglia with no specific orientation to oneanother. In the intestines of control adult, Crohn's,and old age patients, single largecalretinin-immunoreactive neurons are surrounded by anumber of small NADPH-diaphorase-positive neurons, withthis feature being more prominent in intestines ofold-age and Crohn's disease patients. In summary, a high number ofboth NADPH-diaphorase-reactive andcalretinin-immunoreactive neurons were seen in themyenteric ganglia of fetal, old age, and Crohn'sintestines; we discuss that there may be a role for nitric oxide andcalretinin in the process of development, aging, andpathological changes in the human intestine associatedwith alteration in the calcium homeostasis in the myenteric neurons.     

Abnormalities of nerve fibers in the circular muscle of patients with slow transit constipation

Abnormalities of the enteric nervous system are thought to explain the pathophysiology of motility disorders. Our aim was to determine if particular classes of enteric neurons are affected in slow transit constipation (STC). Specimens were taken from the terminal ileum and ascending, transverse and descending colon of patients undergoing subtotal colectomy for STC. Immunohistochemistry was performed using antisera to neuron-specific enolase, tachykinin, leu-enkephalin, choline acetyltransferase, vasoactive intestinal peptide, nitric oxide synthase, tyrosine hydroxylase and neuropeptide Y. The density of nerve fibres labelled with these antibodies in each layer was compared with age-matched controls. The density of nerve fibres with tachykinin and enkephalin immunoreactivity was reduced in the colonic circular muscle of the 15 patients with STC, whereas innervation of all other layers was normal. This reduction of tachykinin-immunoreactive nerve fibres also occurred in nine of the 12 specimens of terminal ileum examined. No difference was detected in the density or distribution of nerve fibres using the other antisera. Excitatory nerve fibres are present in the circular muscle in STC but they are deficient in tachykinins and enkephalin. Accepted: 14 January 1998     

Substance P-immunoreactive peripheral branches of sensory neurons innervate guinea pig sympathetic neurons

The presence of substance P-immunoreactive (SPI) varicose nerve networks and nerve fiber bundles in guinea pig prevertebral sympathetic ganglia has been confirmed by fluorescence immunohistochemistry. No SPI neurons have been found in sympathetic ganglia, including lumbar paravertebral ganglia. Peroxidase-antiperoxidase immunocytochemical methods have shown that SPI nerve terminal varicosities in the inferior mesenteric ganglion (IMG) form morphologically identifiable synapses on dendritic shafts. Cutting the intermesenteric nerve produces no obvious change in SP immunoreactivity in the IMG; cutting the lumbar splanchnic nerves produces nearly total depletion which becomes virtually complete if the two lesions are combined; SP immunoreactivity accumulates in the central ends of the lumbar splanchnic nerves and in the cranial end of the intermesenteric nerve. Cutting hypogastric nerves or colonic branches of the IMG leads to accumulation of SP immunoreactivity in their ganglionic stumps and to build-up (colonic nerve lesion) rather than depletion of SP immunoreactivity in the IMG. Capsaicin treatment leads to total loss of SP immunoreactivity from the prevertebral ganglia and dorsal root ganglia, severe depletion in laminae I and II and dorsolateral fasciculus of the spinal cord, and total loss from perivascular and paravascular networks of the ileum and mesentery, with sparing of the SP immunoreactivity of the enteric nerve plexuses. Capsaicin is thought to deplete sensory neurons selectively. Removal of the spinal cord below T7 without damage to the dorsal root ganglia leaves the intraganglionic SPI nerve networks and bundles intact. We conclude that these are derived from peripheral processes of sensory neurons and we propose that the SPI synapses in the IMG arise from collateral branches of these sensory peripheral processes. This implies a novel role for these processes, in forming intraganglionically in the prevertebral ganglia synapses which may take part in the reflex control of the viscera, independently of the central nervous system.     

Effect of chagas' disease on nitric oxide-containing neurons in severely affected and unaffected intestine

PURPOSE: The pathophysiology of Chagas' disease is incompletely understood. Neuronal nitric oxide has been cited as a candidate neurotransmitter responsible for relaxation of the internal anal sphincter. Neuronal nicotinamide adenine dinucleotide phosphate diaphorase can be used as a marker for neuronal nitric oxide synthase. This study was designed to examine the alterations of the nitric oxidecontaining neurons in the enteric nervous system of the colon of patients who underwent resections for advanced megacolon and to compare these specimens with small-bowel specimens from the same patients and with specimens from control subjects. METHODS: Specimens from resected rectum and extramucosal small-bowel biopsy specimens from 11 patients with Chagas megacolon but no apparent small-bowel clinical involvement were compared with the uninvolved colon and jejunum of 10 control patients with colon cancer. Tissues were fixed in Zamboni solution and evaluated by histochemistry for nicotinamide adenine dinucleotide phosphate diaphorase-containing neurons. Reactivity was evaluated on a 0 to 4 scale in the longitudinal muscle, myenteric plexus, circular muscle, submucosal plexus, and mucosa. RESULTS: Specimens from control patients showed well-stained myenteric and submucosal neurons and an abundant network of terminal nerve fibers in the muscle layers. Chagasic specimens had decreased staining in all layers of the gut. Overall there was a statistically significant decrease in nicotinamide adenine dinucleotide phosphate diaphorase-containing neurons. Biopsy specimens from clinically uninvolved small bowel of patients with Chagas' disease also showed decreased reactivity, but to a lesser degree. CONCLUSIONS: Nicotinamide adenine dinucleotide phosphate diaphorase activity is decreased in patients with advanced megacolon. The alterations are more relevant in the myenteric plexus and the circular muscle. Reactivity is also diminished in the clinically uninvolved small bowel, but to a lesser extent.     

Localization of NADPH-diaphorase in the rat pineal gland: An experimental enzyme histochemical study

Abstract: We have used the NADPH-diaphorase enzyme histochemical technique to localize the enzyme nitric oxide synthase in the rat pineal gland. Some scattered NADPH-diaphorase positive pineal cells were present, mostly in the rostral part of the gland close to the pineal stalk. In addition, NADPH-diaphorase positive nerve fibers were located in the pineal capsule, in the connective tissue septae of the gland, and also intraparenchymally between the pinealocytes. Most nerve fibers were endowed with boutons en passage. These nerve fibers remained in the gland after bilateral removal of the superior cervical ganglia verifying a non-sympathetic nature of the NADPH-diaphorase positive nerve fibers. Pineal blood vessels also exhibited NADPH-diaphorase activity. The number and distribution of NADPH-diaphorase containing cells and nerve fibers were not affected by bilateral superior cervical ganglionectomy. Furthermore, animals sacrificed during day or night exhibited the same NADPH-diaphorase pattern. The present investigation provides the first morphological evidence for the presence of NADPH-diaphorase activity in rat pineal cells, suggesting an influence of nitric oxide on pineal metabolism. Furthermore, the presence of NADPH-diaphorase activity in the pineal blood vessels as well as in the perivascular nerve fibers suggests an influence of nitric oxide on the blood flow to the gland and/or the metabolism of the pineal cells adjacent to the blood vessels.     

Rectal intraganglionic laminar endings are transduction sites of extrinsic mechanoreceptors in the guinea pig rectum

BACKGROUND & AIMS: Vagal afferent mechanoreceptors in the upper gut have recently been identified morphologically as intraganglionic laminar endings (IGLEs), but little is known about the structure of mechanoreceptive endings elsewhere in the gastrointestinal tract. We have morphologically characterized the nerve endings of specialized mechanoreceptors in the rectum. METHODS: Extracellular recordings from guinea pig rectal and colonic nerves were made, in vitro, in combination with rapid anterograde transport of biotinamide, to reveal the morphology of recorded fibers. Controlled distentions were used to activate mechanoreceptive afferent units, and von Frey hairs were used to identify their transduction sites. RESULTS: Rectal mechanoreceptors were present in high density, had low thresholds, and adapted slowly to maintained distention. Each afferent unit had multiple small (<200 microm diameter) transduction sites ("hot spots") at which they could be activated locally by application of a light von Frey hair (0.08-7 mN). Anterograde dye filling revealed characteristic rectal intraganglionic laminar endings (rIGLEs) in myenteric ganglia, significantly associated with hot spots, comparable to the IGLEs of vagal tension receptors, but smaller and less complex. Afferent fibers with these morphologic and physiologic features could not be recorded from colonic nerves innervating the large bowel proximal to the rectum. CONCLUSIONS: The rectum receives a dense afferent innervation by a distinct population of low-threshold, slowly adapting mechanoreceptors with specialized intraganglionic laminar endings (rIGLEs), which are not found more proximally in the colon.