Some observations on the intrinsic nervous mechanism in Hirschsprung's disease

The zebrafish mutant lessen: an experimental model for congenital enteric neuropathies

BACKGROUND

Congenital enteric neuropathies of the distal intestine (CEN) are characterized by the partial or complete absence of enteric neurons. Over the last decade, zebrafish has emerged as a leading model organism in experimental research. Our aim was to demonstrate that the mutant zebrafish, lessen, expressing CEN characteristics, is an equally valuable animal model alongside mammalian models for CEN, by studying its enteric phenotype.

METHODS

The effect of the lessen mutation on the development of the enteric nervous system (ENS), interstitial cells of Cajal (ICC), and intestinal motility in each intestinal region of mutant and wild-type (wt) zebrafish embryos at 3-6 dpf, was analyzed by immunofluorescent detection of neurochemical markers and motility assays.

KEY RESULTS

Development of intestinal motility in the mutant was delayed and the majority of the observed contractions were disturbed. A significant disturbance in ENS development resulted in a distal intestine that was almost free of neuronal elements, in reduced neuronal density in the proximal and mid-intestine, and in a defect in the expression of neurochemical markers. Furthermore, markedly disturbed development of ICC gave rise to a less dense network of ICC.

CONCLUSIONS & INFERENCES

The observed alterations in intestinal motility, intrinsic innervation and ICC network of the mutant in comparison with the wt zebrafish, are similar to those seen in the oligo- and aganglionic regions of the intestine of CEN patients. It is concluded that the zebrafish mutant lessen is an appropriate animal model to investigate CEN.

Purinergic signalling in the gastrointestinal tract and related organs in health and disease

Purinergic signalling plays major roles in the physiology and pathophysiology of digestive organs. Adenosine 5'-triphosphate (ATP), together with nitric oxide and vasoactive intestinal peptide, is a cotransmitter in non-adrenergic, non-cholinergic inhibitory neuromuscular transmission. P2X and P2Y receptors are widely expressed in myenteric and submucous enteric plexuses and participate in sympathetic transmission and neuromodulation involved in enteric reflex activities, as well as influencing gastric and intestinal epithelial secretion and vascular activities. Involvement of purinergic signalling has been identified in a variety of diseases, including inflammatory bowel disease, ischaemia, diabetes and cancer. Purinergic mechanosensory transduction forms the basis of enteric nociception, where ATP released from mucosal epithelial cells by distension activates nociceptive subepithelial primary afferent sensory fibres expressing P2X3 receptors to send messages to the pain centres in the central nervous system via interneurons in the spinal cord. Purinergic signalling is also involved in salivary gland and bile duct secretion.

Intracellular calcium mobilization of the aganglionic intestine in the endothelin B receptor gene-deficient rat

BACKGROUND AND AIM

Up to now, numerous reports have analyzed the pathogenesis of Hirschsprung's disease (HD) by means of physiologic, pathologic, or molecular biologic methods. However, very little is still known about the smooth muscle cell itself. The endothelin B receptor gene-deficient (EDNRB(-/-)) rat, which is suitable for research of HD, has an aganglionic segment of the total colon. Our purpose is to investigate the myogenic mechanisms using simultaneous measurements of the intracellular Ca2+ concentration ([Ca2+]i) and tension and reverse transcriptase polymerase chain reaction for L-type Ca2+ channel (L-VOC) expression.

METHODS

The muscle strips of the rat distal colon were loaded with a Ca2+ indicator dye, fura-PE3/AM, for 3 to 4 hours. The changes in the fluorescence intensity of Ca2+-fura-PE3 complex of the strips were monitored with a front surface fluorometer (CAM-230). The fluorescence intensities at 340- and 380-nm excitation and their ratio (F340/F380) were recorded as the level of [Ca2+]i. The comparison of L-VOC alpha1c subunit messenger RNA (mRNA) expression in both wild and homozygous rat was performed by reverse transcriptase polymerase chain reaction.

RESULTS

The peak levels of force development induced by carbachol were 139.1% +/- 5.0% in EDNRB(-/-) rat, whereas the peak levels were 242.1% +/- 27.7% in EDNRB(+/+) rat. The changes in the [Ca2+]i elevation induced by carbachol were 101.7% +/- 12.2% in the homozygous rat, whereas these were 143.8% +/- 8.9% in the wild-type rat. Both results in the homozygous rat significantly decreased in comparison with those of the wild rat (P < .05). The expression of the L-VOC channel mRNA also decreased in the homozygous rat.

CONCLUSIONS

This is the first report to show the [Ca2+]i mobilization in the smooth muscles of the rat model of HD. The decrease in both [Ca2+]i and force development was thus considered to be due to the decrease in the Ca2+ channel expression.

Universal distribution of c-kit-positive cells in different types of Hirschsprung's disease

Interstitial cells of Cajal (ICCs) have been reported to play the role of a pacemaker in regulating bowel motility. The relationship between neurons and ICCs, however, remains unclear. Hirschsprung's disease (HD) is an ideal model for investigating this relationship. The operated specimens obtained from 6 short and 3 long segment aganglionosis patients and 3 controls were used as the subject materials in this study. ICCs were immunohistochemically identified using a specific antiserum c-kit, a tyrosine kinase receptor expressing ICCs. Nitrergic nerves were demonstrated by NADPH-diaphorase (NADPH-d) histochemistry. C-kit immunohistochemistry was also combined with protein gene product 9.5 (PGP 9.5; as a general neuronal marker). In the normoganglionic segment of HD, numerous c-kit-positive cells and NADPH-d positive neurons were found in the proper muscle layer, including Auerbach's plexus. In the oligoganglionic segment, the number of c-kit-positive cells and NADPH-d neurons slightly decreased. In the inner border of the circular muscle layer (IBCM), the c-kit-positive cell networks and NADPH-d activities remained in short segment cases, while both of them were absent in the long segment cases. In the aganglionic segment, c-kit positive cells were present universally but the number of them was slightly decreased in the proper muscle layer. The c-kit-positive cell networks of IBCM were seen where extrinsic neurons were present, while they were almost completely absent where extrinsic neurons were absent in the proximal zone of the long segment cases. C-kit positive cells were present universally in the oligoganglionic as well as aganglionic segments of HD. The distribution and properties of c-kit positive cells were related to the presence of extrinsic neurons in aganglionic segment. Based on these findings, aperistalsis is considered not to relate with c-kit positive cells, and c-kit positive cells are not supposed to have a neurogenic origin and can develop without neurons, however the lack of enteric neurons may influence the full differentiation of ICCs.

Electrophysiological properties of the aganglionic segment in Hirschsprung's disease

BACKGROUND

In Hirschsprung's disease, the severity of bowel obstruction varies among those patients who have the affected colon of a similar length, suggesting that there is more than a simple aperistaltic obstruction in the pathophysiology of Hirschsprung's disease.

METHODS

A series of our electrophysiological studies of the aganglionic segments from human specimens and rat models were reviewed to obtain an overview of Hirschsprung's disease.

RESULTS

In human studies, a generation of regular spontaneous activity was recorded in both the dilated ganglionic segment and transitional aganglionic region, while the smooth muscle cells of the narrow aganglionic segment were electrically quiescent. According to a pattern of innervation, in the dilated ganglionic segment inhibitory junction potentials associated with or without excitatory junction potentials were observed in all of the examined cells, and these intrinsic nervous inputs were gradually decreased in the transitional region. In the narrow aganglionic segment, only excitatory junction potentials of the extrinsic nervous origin were found in about 20% of the examined cells In rat models, distally increasing tendency of the excitatory nervous inputs was observed in the narrow aganglionic segment.

CONCLUSION

A bowel obstruction in Hirschsprung's disease might be generated due to complex mechanisms involving myogenic and neurogenic abnormalities.

SOX10 is abnormally expressed in aganglionic bowel of Hirschsprung's disease infants

BACKGROUND

The primary pathology of Hirschsprung's disease (HD) is a congenital absence of ganglion cells in the caudal most gut. The spastic aganglionic bowel is often innervated by a network of hypertrophied nerve fibres. Recently, mutations of SOX10 have been identified in patients with HD but only in those with Waardenburg-Shah syndrome.

AIMS

To understand the molecular basis for the pathogenesis of HD we intended to determine the specific cell lineages in the enteric nervous system which normally express SOX10 but are affected in disease conditions.

METHODS

We studied colon biopsies from 10 non-syndromic HD patients, aged three months to four years, and 10 age matched patients without HD as normal controls. The absence of mutation in the SOX10 gene of HD patients was confirmed by DNA sequencing. Expression and cellular distribution of SOX10 in bowel segments of normal and HD infants were examined by reverse transcription-polymerase chain reaction and in situ hybridisation.

RESULTS

We found that in normal infants and normoganglionic bowel segments of HD patients, SOX10 was expressed in both neurones and glia of the enteric plexuses and in the nerves among the musculature in normal colon. In the aganglionic bowel segments of patients, SOX10 expression was consistently lower and was found to be associated with the hypertrophic nerve trunks in the muscle and extrinsic nerves in the serosa.

CONCLUSION

We conclude that SOX10 is normally required postnatally in the functional maintenance of the entire enteric nervous system, including neurones and glia. In non-syndromic HD patients who do not have the SOX10 mutation, the SOX10 gene expressed in the sacral region may be involved in the pathogenesis of the abnormal nerve trunks through interaction with other factors.

Characterization of a novel mechanism accounting for the adverse cholinergic effects of the anticancer drug irinotecan

1. This study investigates the mechanisms accounting for the adverse cholinergic effects of the antitumour drug irinotecan. The activity of irinotecan and its active metabolite, 7-ethyl-10-hydroxy-camptothecin (SN-38), was assayed in models suitable for pharmacological studies on cholinergic system. 2. Irinotecan moderately inhibited human or electric eel acetylcholinesterase activity, SN-38 had no effect, whereas physostigmine blocked both the enzymes with high potency and efficacy. 3. Irinotecan and SN-38 did not affect spontaneous or electrically-induced contractile activity of human colonic muscle. Acetylcholine and dimethylphenylpiperazinium (DMPP) caused phasic contractions or relaxations, respectively. Physostigmine enhanced the motor responses elicited by electrical stimulation. 4. Although irinotecan and SN-38 did not modify the basal contractile activity of guinea-pig ileum longitudinal muscle strips, irinotecan 100 microM moderately enhanced cholinergic twitch contractions. Acetylcholine or DMPP caused phasic contractions, whereas physostigmine enhanced the twitch responses. Electrically-induced [(3)H]-acetylcholine release was reduced by irinotecan (100 microM) or physostigmine (0.1 microM). 5. Intravenous irinotecan stimulated gastric acid secretion in rats, but no effects were obtained with SN-38, physostigmine or i.c.v. irinotecan. Hypersecretion induced by irinotecan was partly prevented by ondansetron, and unaffected by capsazepine. In the presence of atropine, vagotomy and systemic or vagal ablation of capsaicin-sensitive afferent fibres, irinotecan did not stimulate gastric secretion. 6. The present results indicate that irinotecan and SN-38 do not act as specific acetylcholinesterase blockers or acetylcholine receptor agonists. It is rather suggested that irinotecan promotes a parasympathetic discharge to peripheral organs, mediated by capsaicin-sensitive vagal afferent fibres, and that serotonin 5-HT(3) receptors are implicated in the genesis of vago-vagal reflex triggered by irinotecan.

Plasticity in the enteric nervous system

Enteric ganglia can maintain integrated functions, such as the peristaltic reflex, in the absence of input from the central nervous system, which has a modulatory role. Several clinical and experimental observations suggest that homeostatic control of gut function in a changing environment may be achieved through adaptive changes occurring in the enteric ganglia. A distinctive feature of enteric ganglia, which may be crucial during the development of adaptive responses, is the vicinity of the final effector cells, which are an important source of mediators regulating cell growth. The aim of this review is to focus on the possible mechanisms underlying neuronal plasticity in the enteric nervous system and to consider approaches to the study of plasticity in this model. These include investigations of neuronal connectivity during development, adaptive mechanisms that maintain function after suppression of a specific neural input, and the possible occurrence of activity-dependent modifications of synaptic efficacy, which are thought to be important in storage of information in the brain. One of the applied aspects of the study of plasticity in the enteric nervous system is that knowledge of the underlying mechanisms may eventually enable us to develop strategies to correct neuronal alterations described in several diseases.

The distribution and co-localization of nitric oxide synthase and vasoactive intestinal polypeptide in nerves of the colons with Hirschsprung's disease

The distribution and co-localization of nitric oxide synthase (NOS) and vasoactive intestinal polypeptide (VIP) were examined by means of immunohistochemistry and NADPH diaphorase (NADPH-d) histochemistry in the gut of patients with Hirschsprung's disease. In the normoganglionic segment, many nitrergic nerve cells were localized in Auerbach's plexus and nerve fibres were observed preferentially in the circular muscle. The submucosal nitrergic nerve cells were mainly situated in Schabadasch's plexus with occasional cells demonstrable in Meissner's plexus. NOS and VIP were co-localized in most ganglion cells of Auerbach's plexus. In the oligoganglionic segment, a marked reduction of NOS- and VIP- positive nerve cells and fibres was noticed in both the myenteric and submucosal plexuses, and nitrergic fibres had disappeared in the inner layer of the circular muscle. In the aganglionic segment, NOS and VIP were revealed only in extrinsic nerve fasciculi and rami and co-localized in a few fibres. From these observations, the inner layer of the circular muscle of the oligoganglionic segment and the whole of the muscularis propria of the aganglionic segment were considered to be totally lacking in nitrergic innervation. Nitrergic nerves of the human colon comprise both intrinsic and extrinsic elements and the majority of intrinsic nitrergic nerve cells contain VIP. Very low numbers of extrinsic nitrergic fibres contain VIP.

Cyclic GMP relaxes the internal anal sphincter in Hirschsprung's disease

In Hirschsprung's disease (HD), the aganglionic colon and internal anal sphincter (IAS) fail to relax. Aganglionic colon of HD patients relaxes in response to exogenous nitric oxide (NO), whereas the IAS from HD patients does not relax. The authors hypothesized that the failure of IAS relaxation is caused by a local deficiency of cyclic guanosine monophosphate (cGMP), the final metabolite in NO-mediated smooth muscle relaxation. To test this hypothesis, the authors measured the isometric tension of smooth muscle strips taken from the IAS and aganglionic colon of patients with HD before and after exposure to cGMP and compared this with ganglionic colon and IAS from normal controls. In HD patients both the IAS and aganglionic colon relaxed in response to cGMP (P < .05). The amount of relaxation observed in both the aganglionic colon and IAS was comparable to that measured in the normal controls. The observation that exogenous cGMP relaxes the IAS, whereas exogenous NO does not, suggests that mechanisms for relaxation may be different than those in the aganglionic colon and may explain persistent IAS dysfunction after resection of aganglionic colon. The defect of the IAS in HD may be the inability of the NO/cGMP pathway to induce smooth muscle cell relaxation rather than a defect in the smooth muscle cell.

Effect of nitric oxide on the colonic smooth muscle of patients with Hirschsprung's disease

Hirschsprung's disease results in bowel obstruction because of a failure of smooth muscle relaxation in both the aganglionic segment of bowel and the internal anal sphincter (IAS). Nonadrenergic noncholinergic (NANC) nerves, which use nitric oxide (NO) as their chemical messenger, are responsible for relaxing smooth muscle in normal bowel and the IAS. Previous work indicates that the cause of the aganglionic colon's inability to relax may be a lack of NANC nerves. To test this hypothesis, the authors compared the effect of an exogenous source of NO, S-nitroso-N-acetylpenicillamine (SNAP), on the isometric tension of smooth muscle strips taken from the ganglionic colon, aganglionic colon, and IAS of patients with Hirschsprung's disease. Exposure of ganglionic and aganglionic colon specimens to SNAP (10(-3) to 10(-5) mol/L) resulted in up to 70% reduction of resting tension. This relaxation occurred in a dose-dependent fashion and could be promptly reversed by the addition of the NO antagonist methylene blue. However, SNAP had no demonstrable effect on the smooth muscle strips taken from the IAS of patients with Hirschsprung's disease. This finding suggests that, in the aganglionic colon, a deficiency of NANC nerves contributes to the development of bowel obstruction. However, the failure of the IAS to relax in Hirschsprung's disease appears to be unrelated to NO and the NANC nervous system.

Hirschsprung's disease: clinical and experimental observations

Hirschsprung's disease (HD) is a relatively common cause of intestinal obstruction in the newborn. It is characterized by an absence of ganglion cells in the distal bowel beginning at the internal sphincter and extending proximally for varying distances. The etiology of HD-associated enterocolitis remains a complex issue. This study has provided further support for a possible infectious etiology of enterocolitis complicating HD.

Segmental distribution of colonic neuropeptides in Hirschsprung's disease

Despite continued research, the pathophysiologic mechanism responsible for functional obstruction in the aganglionic segment of bowel in Hirschsprung's disease remains controversial. Narrowing of the affected segment is thought by many investigators to be the result of loss of intrinsic inhibitory innervation. For this hypothesis to be consistent, inhibitory neuropeptides should be present in the dilating, transitional segment of bowel. In order to quantitate reported changes in peptidergic nerve staining in Hirschsprung's disease, we measured concentrations of five neuropeptides (vasoactive intestinal peptide, peptide histidine-methionine, met5-enkephalin, substance P and bombesin-like immunoreactivity) by radioimmunoassay in the affected segments of bowel from six patients with Hirschsprung's disease. Tissue extracts were prepared using gut obtained at surgery from the: (1) constricted, aganglionic segment, (2) dilating, aganglionic transitional segment and (3) dilated, proximal ganglionic segment. Concentrations of vasoactive intestinal peptide, peptide histidine-methionine, substance P and met5-enkephalin were significantly reduced in both the muscularis externa and the mucosal-submucosal layers from the constricted aganglionic segment. By contrast, concentrations of the candidate inhibitory neuropeptides, vasoactive intestinal peptide and peptide histidine-methionine, were minimally reduced in the dilating, aganglionic transitional segment. These results are consistent with the hypothesis that constriction of the aganglionic segment is due to loss of intrinsic inhibitory innervation. Concentrations of bombesin-like immunoreactivity were similar in the three segments of human gut, suggesting the presence of this immunoreactive neuropeptide in extrinsic nerve fibers.

NPY hyperinnervation in Hirschsprung's disease: both adrenergic and nonadrenergic fibers contribute

In Hirschsprung's disease, the aganglionic bowel is characterized by an absence of ganglion cells and an increased number of adrenergic and presumed cholinergic nerve fibers. In addition, a severe derangement of peptide-containing nerve fibers is encountered including a hyperinnervation of neuropeptide Y (NPY)-containing fibers. Using immunochemical and immunocytochemical methods, we examined the nature of the NPY-containing nerve fibers contributing to the hyperinnervation. The concentration of NPY was markedly increased in the aganglionic segment. Coexistence of NPY, vasoactive intestinal peptide (VIP), and the adrenergic enzyme tyrosine hydroxylase (TH) showed small populations of nerve fibers containing NPY/TH, NPY/VIP, or TH alone in ganglionic intestine. Numerous nerve fibers stored VIP but lacked NPY. These fibers did not contain TH, indicating that all VIP-containing fibers are nonadrenergic. In the aganglionic intestine there was a marked increase in the number of nerve fibers storing NPY/TH and NPY/VIP, whereas the fibers storing VIP alone were reduced in number. A small number of nerve fibers storing NPY alone occurred in the hypertrophic nerve bundles. NPY/VIP-containing nerve fibers were particularly numerous in the mucosa in aganglionic intestine, which may be of interest in the diagnosis of Hirschsprung's disease allowing the use of mucosal biopsy specimens. Thus, the proliferating NPY-containing nerve fibers in the aganglionic intestine seem to comprise three different populations, one adrenergic and two nonadrenergic, one of which contains in addition VIP.

Physiology and pathophysiology of colonic motor activity (2)

The basic motor function of the colon is to mix and knead its contents, propel them slowly in the caudad direction, hold them in the distal colon until defecation, and provide a strong propulsive force during defecation. Infrequently, it also produces mass movements in the proximal colon. These motor functions are achieved in most species by three different types of contractions: the individual phasic contractions that include the short- and long-duration contractions, organized groups of contractions that include the migrating and nonmigrating motor complexes, and special propulsive contractions (giant migrating contractions). The spatial and temporal patterns of all of these contractions are controlled by myogenic, neural, and chemical control mechanisms. The individual phasic contractions are highly disorganized in time and space in the colon. For this reason, they are effective in mixing and kneading and slow distal propulsion. The underlying cause of the disorganization of short duration contractions is the irregularity in the frequency and waveshape of colonic electrical control activity and its phase unlocking throughout the colon. The individual contractions in many species occur in cyclic bursts called contractile states. At least in some species, these contractile states exhibit mostly caudad and sometimes orad migration. However, there are also nonmigrating or randomly migrating contractile states in the colon. These two patterns of contractile states are called colonic migrating motor complexes and colonic nonmigrating motor complexes, respectively. The giant migrating contractions provide the strong propulsive force for defecation and mass movements. The neural control of colonic contractions is organized at three levels--enteric, autonomic, and central. The enteric nervous system contains cholinergic and peptidergic neurons and plays a major role in the control of colonic contractions. The autonomic nerves, the vagi, pelvic, lumbar colonic, hypogastric, and splanchnic nerves, seem to continuously monitor the state of the colon and provide a modulatory input when necessary. These nerves play a major role in the reflexive control of colonic motor function. The voluntary input from the central nervous system coordinates the motor activity of the colon, rectum, anal canal and sphincters for orderly evacuation of feces during defecation. The role of acetylcholine, nonadrenaline, and the yet to be completely identified nonadrenergic, noncholinergic neurotransmitter, possibly VIP, in the control of contractions is fairly well established. Besides these, there are several other peptides and chemicals that are localized in the colonic wall; their physiological roles remain unknown. Colonic motor activity has been studied in several disease states. The findings have not always been consistent.(ABSTRACT TRUNCATED AT 400 WORDS)

Characteristics of cholinergic neuroeffector transmission of ganglionic and aganglionic colon in Hirschsprung's disease

Differences in the release and content of acetylcholine and the alpha 2 adrenoceptor mediated interaction between noradrenergic and cholinergic neurons were investigated by neurochemical and pharmacological methods in aganglionic and ganglionic segments of isolated human colon taken from children suffering from Hirschsprung's disease. Both at rest and during transmural stimulation the release of acetylcholine was significantly higher in the spastic (aganglionic) segment than in the proximal dilated bowel. Significant differences were found in the tissue concentration of acetylcholine between ganglionic and aganglionic specimens. The pattern of response to transmural stimulation was also different in the spastic and dilated bowel. Transmural stimulation induced relaxation and contraction in ganglionic specimens but only contractions in aganglionic specimens. The sensitivity of the smooth muscle in the aganglionic portion to exogenous acetylcholine and to field stimulation was found to be higher than in the ganglionic portion. While noradrenaline added to the organ bath reduced the stimulation-evoked release of acetylcholine from spastic segments, via an alpha 2 adrenoceptor mediated process, yohimbine did not enhance the release. It is suggested that in Hirschsprung's disease the increased acetylcholine release, the enhanced sensitivity of smooth muscle cells to acetylcholine, and the lack of alpha 2 adrenoceptor mediated noradrenergic modulation of acetylcholine release from cholinergic interneurons might be responsible for the spasm of aganglionic segments.

Regional differences in the pattern of neurogenic responses in the aganglionic colon from congenitally aganglionic rats

The pattern of innervation in the aganglionic colon and internal anal sphincter from cogenitally aganglionic rats was studied and compared with that of control littermates. In normoganglionic colon and anal sphincter, electrical stimulation evoked excitatory or inhibitory junction potentials followed by a contraction or relaxation, respectively. These responses were abolished by tetrodotoxin and atropine selectively abolished the excitatory effects, indicating that the colon or anal sphincter is innervated by intrinsic cholinergic excitatory and noncholinergic inhibitory nerves. In congenitally aganglionic rats, electrical stimulation evoked excitatory and inhibitory responses in sphincteric regions, while only excitatory responses were observed in distal segments. Excitatory responses were weak in proximal segments of the aganglionic colon and electrical stimulation failed to evoke neurogenic responses. These results indicate regional differences in the functional innervation of extrinsic nerve fibers in the aganglionic colon from congenitally aganglionic rats and the usefulness of congenitally aganglionic rats as an animal model for Hirschsprung's disease.

Function of smooth muscle and nerve after small intestinal transplantation in the rat: effect of storing donor bowel in Eurocollins

Lewis rats received syngeneic heterotopic grafts of jejunum immediately, or after preservation for 24 or 48 hours in Eurocollins solution. Most recipients of tissue stored for 0 or 24 hours remained healthy. Longer storage caused death of the recipients. We evaluated the effect of tissue preservation by comparing grafts stored for 0 and 24 hours with control jejunum at successive intervals up to ten days after transplantation. The physiology and pharmacology of smooth muscle and nerve endings were studied in vitro. Circular and longitudinal muscle in all specimens contracted in response to cholinergic agonists, phenylephrine, and substance P, and was relaxed by isoproterenol and noradrenaline. 5-hydroxytryptamine caused contraction of longitudinal muscle in all cases, and of both muscle layers in grafts that had been stored prior to transplantation. In all grafts, the excitatory innervation was similar to control, while the extrinsic adrenergic inhibition was absent. Prior storage caused an additional loss of intrinsic nonadrenergic inhibition, but this recovered within eight days. These findings indicate that Eurocollins solution might be a useful vehicle for the preservation of donor intestine prior to transplantation, as long as the period of storage does not exceed 24 hours.

Vasoactive intestinal peptide (VIP), a putative neurotransmitter of nonadrenergic, noncholinergic (NANC) inhibitory innervation and its relevance to therapy

Nonadrenergic, noncholinergic (NANC) innervation, the third division of the autonomic nervous system, has both inhibitory and excitatory parts. The excitatory part received only limited attention. Substance P has been suggested to be the neurotransmitter of the excitatory part. The NANC-inhibitory innervation has recently been studied in detail. Although the neurotransmitter has not been conclusively identified, a substantial body of evidence exists to support vasoactive intestinal peptide (VIP) as the neurotransmitter. VIP is widely distributed in the body. Reports show that this innervation in animals and man plays a significant role in both health and disease. Pathological conditions could result from either an increase or decrease in VIP production. An absence of VIP-producing neurons has been identified to be responsible for Hirschsprung's disease in the alimentary system and hyperactive airways in the respiratory system. An increase in VIP production is associated with chronic water diarrhea syndrome in humans. Taking these factors into consideration, various therapeutic measures are suggested with the use of VIP or its antagonists.

Studies of the inhibitory non-adrenergic neuromuscular transmission in the smooth muscle of the normal human intestine and from a case of Hirschsprung's disease

A modified sucrose-gap method was used to study both non-adrenergic inhibitory neuromuscular transmission and effects of adenosine 5'-triphosphate (ATP) on isolated smooth muscle preparations from the human intestine. It was found that non-adrenergic inhibition in the circular smooth muscle layer was of larger amplitude than in the longitudinal layer. Study of the ionic mechanisms underlying non-adrenergic inhibition indicated that an increase in K+ conductance was responsible for the generation of non-adrenergic inhibitory junction potentials (IJPs). The results suggest that the inhibitory actions of the endogenous neurotransmitter and exogenous ATP are due to increases in Ca2+-dependent K+ conductance. The K+-channel blockers tetraethylammonium and 4-aminopyridine had no effect on IJPs or ATP, while apamin slightly decreased both the amplitude of the IJP and the hyperpolarization of the circular smooth muscle caused by ATP. These results are consistent with the purinergic hypothesis of non-adrenergic inhibition. In addition to inhibitory purinoceptors, the existence of excitatory purinoceptors was identified in the longitudinal muscle, activation of which probably caused an increase in Na+-conductance. The excitatory purinoceptor-mediated contraction in the longitudinal muscle from the constricted region of large intestine from patients with Hirschsprung's disease was greater than that found in control specimens. It is possible that excitatory purinoceptors play a role in the pathophysiology of Hirschsprung's disease.

Distribution, quantitation, and origin of immunoreactive neuropeptide Y in the human gastrointestinal tract

A radioimmunoassay for measurement of immunoreactive neuropeptide Y has been developed using antiserum from a rabbit (221) immunized with porcine neuropeptide Y. Antibody 221 has been characterized for both sensitivity and specificity. To determine the distribution of neuropeptide Y in the human gastrointestinal tract, fresh tissue specimens were separated by microdissection into the muscularis externa and the mucosa-submucosa. To examine the origin of neuropeptide Y in human colon, specimens of aganglionic and ganglionic colon were obtained from patients with Hirschsprung's disease. Immunoreactive neuropeptide Y in human gut was present in highest concentrations in the muscularis externa of the stomach and in lowest concentrations in the muscularis externa of the ileum and descending colon. Neuropeptide Y in the stomach was present in higher concentrations in the muscularis externa than in the mucosa-submucosa, but in the descending colon there were lower concentrations of neuropeptide Y in the muscularis externa than in the mucosa-submucosa. In Hirschsprung's disease, concentrations of neuropeptide Y were increased in aganglionic colon in both the muscularis externa and the mucosa-submucosa, compared to corresponding layers from proximal ganglionic colon. Extracts of the gastric muscularis externa and the colonic mucosa-submucosa were separated by C18 reverse-phase high-performance liquid chromatography. One major immunoreactive species was identified by radioimmunoassay which eluted in a position similar to synthetic human neuropeptide Y. These results demonstrated both regional and layer differences in concentrations of neuropeptide Y in human gut. Increased concentrations of neuropeptide Y in aganglionic colon from Hirschsprung's disease most likely result from enlargement of neuropeptide Y-containing extrinsic nerve fibers in both the mucosa-submucosa and the muscularis externa.

Hirschsprung's disease: a comparison of the nervous control of ganglionic and aganglionic smooth muscle in vitro

Specimens from aganglionic (constricted) and ganglionic (dilated) gut were obtained from nine patients with Hirschsprung's disease. Transmural nerve stimulation of ganglionic smooth muscle in vitro evoked an initial relaxation followed by a contraction. This contraction was reduced but not abolished by atropine and it was further reduced by substance P antagonists. Guanethidine did not affect the electrically evoked responses. In aganglionic smooth muscle, an atropine-sensitive contraction but no initial relaxation was registered. Tetrodotoxin abolished all responses to electrical stimulation in both ganglionic and aganglionic specimens. Application of carbachol or substance P produced contraction and the adrenergic agonist isoprenaline or vasoactive intestinal peptide produced relaxation in ganglionic as well as aganglionic specimens. Two other gut neuropeptides, neuropeptide Y and galanin, were without effect. The results do not indicate a different receptor set up in ganglionic v aganglionic gut. The results are compatible with a lack of noncholinergic nonadrenergic inhibitory neurons in the aganglionic gut.

Distribution of nerves containing vasoactive intestinal polypeptide-like immunoreactivity in rats with congenital aganglionosis of the colon

The distribution of nerves containing vasoactive intestinal polypeptide-like immunoreactivity was examined immunohistochemically in whole-mount specimens of the colons of mutant rats, which completely lacked intramural nerve cells in the colon, and of their normal littermates. In the aganglionic colon, greatly diminished numbers of vasoactive intestinal polypeptide-like immunoreactive nerve fibers were found in the circular muscle layer, lamina propria of the mucosa, and in the submucosa. In the intermuscular space of the aganglionic colon, unlike the pattern of the normal Auerbach's plexus, vasoactive intestinal polypeptide-like immunoreactive nerve fibers were arranged in an irregular, coarse network. These findings suggest the existence of extrinsic nerves containing vasoactive intestinal polypeptide in the aganglionic colon of the hereditary aganglionic rat.

Immunohistochemical characterization of abnormal innervation of colon in Hirschsprung's disease using D7 monoclonal antibody

Innervation patterns in normal and aganglionic colon were studied using a panel of antineuronal cell antibodies. One antibody, D7, which recognizes a subset of neuronal cells of the peripheral and central nervous system reacted strongly with nerve fibers in the circular muscle of the normal colon. Immunohistochemical scanning of the entire resected specimen of colon from three children with Hirschsprung's disease demonstrated large numbers of D7 immunoreactive nerve fibers in the circular muscle of the ganglionic colon, few fibers in the transitional zone, and no immunoreactive fibers in the aganglionic segment of bowel. While the absence of D7 immunoreactive fibers paralleled the absence of myenteric ganglion cells in the aganglionic segment, a critical region of colon was identified wherein D7 reactive fibers were evident ahead of the appearance of ganglion cells. These findings indicate that the fundamental pathology in Hirschsprung's disease is not only the absence of ganglion cells of the myenteric and submucuous plexuses but also the absence of D7 immunoreactive fibers in the circular muscle of the colon.

Functional response to vasoactive intestinal peptide in piebald lethal mice

Diminished concentrations of the gut neuropeptide, vasoactive intestinal peptide (VIP), have been measured by radioimmunoassay in man and mouse models of Hirschsprung's disease. This in vitro study was designed to ascertain the functional response to VIP in aganglionic colon. Seven piebald lethal (PLM) mice with histologically verified aganglionosis and seven normal littermates (NLM) were sacrificed. Distal colonic segments were placed in standard oxygenated tissue baths and responses to electrical field stimulation (EFS), acetylcholine (ACh), and VIP recorded and analyzed by a motility index (MI). Aganglionic colonic tissues from PLM exhibited marked basal contractile activity in contrast to NLM (MI = 19.5 +/- 2.0 SEM v 6.5 +/- 3.6 SEM, P less than .01). In NLM tissues, VIP reduced the MI to ACh challenge by 49% (P less than .01), while in PLM tissues, a nonsignificant 22% reduction was observed. VIP blocked the response to EFS in NLM tissues, while no response was elicited to EFS in PLM tissues. An in vitro deficit in the VIP inhibitory response to ACh challenge is apparent in PLM with distal colonic aganglionosis. The increased basal activity and reduction in responsiveness to VIP, observed in the PLM tissues, support a generalized reduction in the function of the inhibitory innervation of the aganglionic colon.

Nerve mediated responses to drugs and electrical stimulation in aganglionic muscle segments in Hirschsprung's disease

The activity of isolated muscle strips from normal and aganglionic human large bowel was studied in vitro. The intrinsic nerves were stimulated electrically and by nicotinic agonists. The ganglionic preparations displayed a strong inhibitory response due to the release of both norepinephrine and a noncholinergic, nonadrenergic inhibitory neurotransmitter. In the aganglionic strips (obtained from patients with Hirschsprung's disease), nerve activation tended to evoke contraction, apparently due to enhancement in the release of acetylcholine. At the same time, the release of norepinephrine appeared to be less than normal. A particularly interesting finding in the aganglionic muscle strips was the presence of a substantial inhibitory response due to the release of a noncholinergic, nonadrenergic substance. These results provide further evidence for the importance of the innervation of the aganglionic segment in Hirschsprung's disease.

Pharmacological analysis of rebound excitation in large intestine of piebald mouse model for Hirschsprung's disease

Pharmacological agents that might influence the poststimulus rebound contractile response (PSRR) through an action on the intrinsic inhibitory innervation of the circular muscle coat were studied in the large intestine of the piebald mouse model for Hirschsprung's disease. Tetrodotoxin (0.3-3 microM) suppressed, in a dose-dependent manner, the amplitude, duration, and area under the contractile traces of the PSRR and increased the latency for the response in ganglionated segments of the large intestine of piebald and normal mice. Sensitivity to tetrodotoxin was greater in the megacolon of piebald mice than in the colon of normal mice. Norepinephrine (6-360 microM) suppressed all parameters of the PSRR in ganglionated regions of the large intestine of abnormal mice. Sensitivity to norepinephrine was greater in the megacolon than in the colon of normal mice. Norepinephrine abolished spontaneous contractile behavior in ganglionated regions of the large intestine of normal and diseased mice and in the aganglionic segment of the piebald mice. Suppression of the PSRR by phentolamine and propranolol were interpreted as nonspecific local anesthetic effects. Atropine (20-200 microM) increased the area under the contractile traces in the midcolon of the intestine of both normal and piebald mice and had no effects on the terminal segment of the large intestine of normal mice. Spontaneous contractile activity and baseline tension were increased by atropine (350 microM) in all preparations. The nicotinic agonist, DMPP (3-157 microM), suppressed the PSRR in the ganglionated regions of the bowel from both normal and abnormal mice. DMPP relaxed resting tension in ganglionated regions, but did not affect the aganglionic terminal segment of the piebald mouse.(ABSTRACT TRUNCATED AT 250 WORDS)

Hirschsprung's disease: an historical review

A historical review of Hirschsprung's disease is of relevance for several reasons. The historical events are revealing as to how clinical diseases are often slowly unravelled. In addition, many unsolved problems are highlighted. Firstly the exact cause is unknown. There is obviously an interaction between genetic and environmental factors, the nature of which is of interest to basic scientists as well as clinicians. Secondly the pathophysiological explanation for the functional obstruction, and especially its variability, is still incomplete. Much more needs to be known about normal gastrointestinal physiology before this question can be fully answered. Thirdly the technique and timing of operative correction remains inconclusive. Despite extensive postoperative assessment there is no one operation that is clear superior. Each have characteristic problems, but all share the main problem; the abnormal internal sphincter. It remains uncertain how much (if any) of the sphincter should be bypassed. As well the optimal timing of operation is uncertain, with some theoretical advantages being suggested for earlier operation. However, these advantages need to be balanced against possible technical problems. Nevertheless the aim of surgical correction should be the full attainment of normal faecal continence.

Hirschsprung disease: a genetic study

This study examines the association of Hirschsprung disease with Down syndrome and calculates the recurrence risk for families of Hirschsprung patients. Information was collected from 134 histologically diagnosed patients with Hirschsprung disease, from Children's Hospital in Pittsburgh, PA between 1950 and 1977. One hundred and three patients had short segment Hirschsprung disease which is defined as involvement up to and including the sigmoid colon. Thirty-one patients had the long segment type with aganglionosis extending in some cases to the small intestine. As in other studies, we found a significant association between Hirschsprung disease and Down syndrome in that 5.9% of probands had both. Mean maternal age of cases with both Hirschsprung disease and Down syndrome (33.5 years) was significantly different from controls (26.7 years) and non-Down syndrome Hirschsprung patients (26.6 years). The overall sex ratio for Hirschsprung disease was 3.6. Recurrence risks were dependent on proband sex and the degree of aganglionic involvement.

Total intestinal aganglionosis

Total Intestinal Aganglionosis is a rare, uniformly fatal condition with absence of ganglia from the duodenum to the rectum. A neonate with this extreme form of Hirschsprung's disease is presented with a review of 12 previously reported cases. Smooth muscle strips from this infant's gastrointestinal tract demonstrated viable cholinergic receptors, absence of intrinsic neuronal innervation, and colonic contractile activity to the purported peptidergic neurotransmitter cholecystokinin. Four aspects of total intestinal aganglionosis are noteworthy: (1) one-third of patients presented between four and eight days of age after passing meconium on the first day of life; (2) at laparotomy, no intestinal distention, obstruction, or transition zone was evident; (3) hypertrophic nerve fibers seen in classic Hirschsprung's disease were absent in one-quarter of patients; and (4) a high incidence of affected siblings occurred in the previously reported cases. This form of Hirschsprung's disease may represent a distinct entity with autosomal recessive inheritance and significant risk for recurrence.

Qualitative and quantitative analysis of muscarinic acetylcholine receptors in the piebald lethal mouse model of Hirschsprung's disease

Cholinergic innervation in the aganglionic bowel of the piebald lethal mouse model of Hirschsprung's disease was investigated by analysis of muscarinic acetylcholine receptors before and after administration of hexamethonium. After hexamethonium administration in the normal rectum, the maximum specific binding (Bmax) of [3H]quinuclidinyl benzilate increased from 196.6 to 346.2 fmol/mg protein without affecting the dissociation constant. This increase of muscarinic acetylcholine receptors was associated with a decrease in the 50% effective dose (ED50) of contractile response to oxotremorine from 3.8 X 10(-7) M to 6.5 X 10(-8) M. In the aganglionic rectum, hexamethonium administration did not change the Bmax (166.4 fmol/mg protein) or dissociation constant value. The ED50 of contractile response to acetylcholine and oxotremorine (4.3 X 10(-8) M, 6.5 X 10(-8) M) was lower than that in the normal rectum (1.9 X 10(-7) M, 2.0 X 10(-7) M), but it was not changed by hexamethonium. It is concluded that cholinergic innervation is congenitally absent in the aganglionic rectum in piebald lethal mice.

Distribution and quantitation of immunoreactive gut neuropeptides in piebald mice and their normal littermates

Piebald mice inherit congenital megacolon associated with distal aganglionosis. To study the distribution of intrinsic peptidergic nerves in the gut of piebald mice and their normal littermates, we used specific radioimmunoassays to measure the tissue concentrations of the following immunoreactive neuropeptides: vasoactive intestinal peptide (VIP), peptide histidine-isoleucine (PHI), [Met]enkephalin (Enk), substance P (SP), and bombesin-like intestinal peptide (BLIP). In the normal littermates, all neuropeptide concentrations were significantly greater in the colon than in the proximal gut. SP, Enk, VIP, PHI, and BLIP levels were all decreased in the distal colon of piebald mice as compared to normal littermates, SP, BLIP, and Enk levels were also decreased in the dilated proximal colon of piebald mice. These results suggest that there are abnormalities in the peptidergic innervation of the proximal and the distal colon in piebald mice. The abnormalities localized to the proximal colon of piebald mice may be related to functional obstruction of the colon.

An immunohistochemical study of serotoninergic nerves in the colon and rectum of children with Hirschsprung's disease

Serotonin (5-HT)-like immunoreactive nerve fibers were investigated in gut tissue obtained from seven Japanese children with Hirschsprung's disease. In the control untreated tissues, 5-HT-like immunoreactive fibers were observed neither in the normoganglionic nor in the aganglionic regions. After pargyline treatment, 5-HT-positive neuropils were consistently detected in association with the myenteric plexus in the normoganglionic segment, while in the aganglionic segment immunoreactive fibers could not be demonstrated through the entire layer of the bowel tissue. The occurrence of 5-HT-like immunoreactive neuropils by pargyline treatment strongly suggests that the infant bowel is innervated with serotoninergic elements. After treatment with 5-hydroxy-L-tryptophan (5-HTP), the immunoreactive neuropils were localized in the myenteric and submucous plexuses of the normoganglionic segment. On the other hand, another type of 5-HT-positive fibers was characteristically demonstrated in aganglionic segments following the drug treatment; moderate numbers of 5-HT-like immunoreactive fibers appeared in the intermuscular zone and within the circular and longitudinal muscle layers. Several 5-HT-positive fibers were present in the hypertrophic nerve bundles seen in a diseased bowel. A possible origin of this type of 5-HT-positive nerve fibers was discussed.

Immunohistochemical study of neuron specific enolase and S-100 protein in Hirschsprung's disease

The distribution of whole differentiated neurons in the intestines from 15 children with Hirschsprung's disease was investigated using neuron specific enolase (NSE) and the perineuronal elements were studied using S-100 protein immunostaining. In aganglionic segments, NSE immunoreactive ganglion cells and S-100 positive satellite cells were absent, but the hypertrophic nerve trunks did show a markedly positive NSE and S-100 immunoreactivity. Two different forms of aganglionic segment were present. One was the middle aganglionic segment of long segment aganglionosis which was almost completely dennervated. In the other type, there were several NSE positive nerve fibers in the muscularis propria of both the aganglionic segment of short segment aganglionosis and the distal aganglionic segment of long segment aganglionosis. These latter two aganglionic segments seemed to be innervated by extrinsic nerves.

Peptidergic innervation irregularities in Hirschsprung's disease. Immunohistochemistry--radioimmunoassay

The distribution of vasoactive intestinal polypeptide (VIP)-containing nerves and the contents of both VIP and substance P (S-P) in the intestines from 12 children with Hirschsprung's disease were examined using immunohistochemical methods and radioimmunoassay. VIP-containing nerve fibers were markedly decreased in number in the true muscle coats of aganglionic segments, while extrinsic hypertrophic nerve bundles in these segments showed positive VIP-immunoreactivities. This finding suggests the existence of extrinsic origins of VIP-containing nerves in the human gut. The contents of VIP were 44.5 +/- 8.2 in aganglionic segments and 130 +/- 17.1 pg/mg wet tissue weight in normoganglionic segments. The contents of S-P were 0.42 +/- 0.18 in aganglionic segments and 6.38 +/- 2.3 pg/mg wet tissue weight in normoganglionic segments. Both VIP and S-P contents in aganglionic segments were significantly reduced as assessed by the use of radioimmunoassay (p less than 0.001 and p less than 0.05). These abnormal peptidergic patterns of innervation might relate to the non-peristaltic state in Hirschsprung's disease.

A possible role of a nonadrenergic inhibitory nervous system in airway hyperreactivity

To investigate a possible role of a nonadrenergic inhibitory nervous system in airway hyperreactivity, we measured changes in RL and CL caused by electrical stimulation of cervical vagus nerve during the infusion of 5-HT, after treatment with atropine and propranolol in 18 cats. RL decreased to 56 +/- 3% (mean +/- SE) and CL increased to 186 +/- 13% of the prestimulated values, respectively, after stimulation. Hexamethonium diminished these responses significantly. Airway reactivity to 5-HT was reduced by continuous electrical stimulation of cervical vagus nerve in cats pretreated with atropine and propranolol. Hexamethonium potentiated airway reactivity to 5-HT. These results suggest that a nonadrenergic inhibitory nervous system could play an important role in the control of the bronchomotor tone and contribute to airway hyperreactivity.

Abnormalities of the colonic regulatory peptides in Hirschsprung's disease

We describe here a depletion of peptide containing nerves and cells in Hirschsprung's disease, in comparison with specimens of bowel taken from age-matched neonates with no evidence of chronic constipation. VIP content in the diseased specimens was reduced by almost 80%, from 110/+-10.6 (mean +/- SEM) pmol VIP/g wet weight of tissue in controls to 23.8 +/- 3.5 pmol/g in the mid-portion of the diseased specimens. In addition, the numbers of enteroglucagon and somatostatin cells in the mucosa were significantly reduced in the aganglionic portions. Enteroglucagon cells were reduced from 55 +/- 7 in controls to 27 +/- 2 in proximal portions rising to 44 +/- 3 and 49 +/- 4 cells/mm2 in middle and distal areas. Somatostatin cell numbers also fell, from 5.5 +/- 1.9 to 1.8 +/- 0.8, 2.5 +/- 0.7 and 3.8 +/- 0.9 cells/mm2 in similar areas. Further investigation of the abnormalities of the diffuse neuroendocrine system in Hirschsprung's disease may help in understanding the nature of this condition and provide additional information on the role of these peptides in the control of gut function.

Vasoactive intestinal peptide: a possible transmitter of nonadrenergic relaxation of guinea pig airways

Vasoactive intestinal peptide, a smooth-muscle relaxant neuropeptide with neurotransmitter properties, was relaxed during electrical field stimulation of guinea pig trachea. The amount released correlated with the degree of relaxation, and the release was blocked by tetrodotoxin. Prior incubation of the trachea with antiserum to vasoactive intestinal peptide reduced the relaxation. Thus vasoactive intestinal peptide may mediate the nonadrenergic relaxation of tracheal smooth muscle.

A nonadrenergic vagal inhibitory pathway to feline airways

In cats anesthetized with chloralose-pentobarbital and artificially ventilated, electrical stimulation of the caudal end of the cut cervical vagus nerve has a biphasic effect on the bronchoconstriction induced by an intravenous infusion of serotonin. The response consists of a brief augmentation of bronchoconstriction followed by relatively prolonged bronchodilation. After muscarinic receptor blockade with atropine, vagal stimulation causes only bronchodilation. Vagally mediated bronchodilation is not affected by beta adrenergic blockade with propranolol, alpha adrenergic blockade with phenoxybenzamine, or adrenergic neuronal blockade with guanethidine, but is abolished by autonomic ganglionic blockade with hexamethonium. These findings support the conclusion that a nonadrenergic inhibitory nervous system is present in the pulmonary airways of the cat and that the system is supplied by preganglionic fibers in the cervical vagus nerves.

Hirschsprung's disease: absence of serotonergic neurons in the aganglionic colon

The distribution of enteric serotonergic neurons was studied in patients with Hirschsprung's disease. Specimens of bowel obtained at surgery were incubated in vitro with tritiated serotonin (3H-5-HT) in the presence of a high concentration of nonradioactive norepinephrine. Sites of high-affinity 3H-5-HT uptake were visualized by light-microscopic autoradiography. Specimens taken from ganglionic regions of the intestine (distal ileum or colon) showed intense labeling of the neuropil within the myenteric plexus. Silver grains were localized in a pericellular distribution around ganglion cells, but the ganglion cells themselves were relatively free of overlying silver grains. Corresponding regions of aganglionic colon or rectum demonstrated silver grain densities equivalent to background levels. Specific labeling was absent over the large nerve trunks in this region. These results suggest that 5-HT-containing neurons are present in the normal human intestine and that these neurons are absent in the aganglionic segment in Hirshsprung's disease.

Motility of the large intestine of piebald-lethal mice

In normal siblings of piebald mice, artificial fecal pellets were propelled by peristaltic activity through the large intestine in vitro and were expelled at the anal end. Peristalsis was blocked by lidocaine. Artificial fecal pellets were propelled in the dilated region of the megacolon, but were not propelled in the terminal hypoganglionic segment of the intestine of piebald mice. Retropulsion of artificial fecal pellets occurred in vitro in normal bowel obstructed by a ligature, in the bowel of piebald mice with a narrowed terminal segment, and in the intestine of mice with imperforate anus. The results indicate that the distended portion of the colon of piebald mice is capable of coordinated peristalsis and that accumulation of feces and megacolon are secondary to the terminal obstruction that results from absence of coordinated propulsive activity in the hypoganglionic terminal segment. Reverse peristalsis may be a general response to a distal obstruction.

Pharmacologic studies of Hirschsprung's disease on a murine model

In studies of the pharmacology of a murine model of aganglionosis, the contracted aganglionic portion of the terminal bowel showed slow regular contractions of high amplitude in comparison to the rapid low-amplitude contractions of a normal segment of bowel. An absence of the nonadrenergic inhibitory system was demonstrated in the aganglionic, contracted portion of the bowel. This lack of the nonadrenergic system confirms previous findings in human tissue. It is proposed that absence of this inhibitory system in the aganglionic portion of the bowel results in the principal pathophysiologic findings in Hirschsprung's disease.

Pathophysiology of aganglionic colon segment: an experimental study on aganglionosis produced by a new method in the rat

Experimental aganglionosis was produced successfully in a colonic segment proximal to the peritoneal reflection by intraluminal filling under tension of the colorectum of rats with 0.01% corrosive sublimate in normal saline solution. Where the length of aganglionic segment was more than 3 cm, ileus appeared and megacolon proximal to a narrow segment was observed. Histologically and histochemically, a total denervation state was observed in the aganglionic segment, in contrast to findings in narrow segments of Hirschsprung's disease, in which intramural extraneous nerves are known to be increased. The fact that a definite narrow segment like that seen in Hirschsprung's disease appeared at the portion of the colon in which experimental aganglionosis was produced indicates that a narrow colonic segment certainly can be produced without presence of any intramural extraneous nerves, although the possibility that the presence of such nerves may exaggerate the narrowing cannot be denied. The fact that the cases in which length of aganglionosis was less than 2.5 cm did not have an ileus suggests that there may be some contributing factors other than aganglionosis in the etiology of Hirschsprung's disease of ultrashort segment, if this entity of the disease really exists. Aperistalsis observed in experimental aganglionic segments and that observed in aganglionotic segments of Hirschsprung's disease seem to be based on a common main factor, i.e., absence of the nonadrenergic, noncholinergic nerves.

Demonstration of a nonadrenergic inhibitory nervous system in the trachea of the guinea pig

A nonadrenergic inhibitory nervous system has been demonstrated in the guinea pig trachea. Electrical field stimulation of this system, in the presence of adrenergic and cholinergic blockade, resulted in relaxation of tracheal rings contracted by the mediators of immediate hypersensitivity or histamine. The relaxation was blocked by tetrodotoxin, which indicated that nerve stimulation was responsible for the relaxation. The gastrointestinal tract, which has a similar embryological origin to the respiratory tract, also has a nonadrenergic inhibitory system. In the gastrointestinal tract, this system is thought to be responsible for the relaxation phase of peristalsis, and absence of this system, in the colon and the rectum, is thought to be an explanation for the spastic bowel in Hirschsprung's disease. It is possible that an abnormality of the respiratory nonadrenergic inhibitory system may play a role in the pathogenesis of the hyperreactive airways in asthma. The airways, due to a lack of inhibition, may be either partially contracted or unable to relax, and thus appear hyperreactive to stimuli.