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Decreased density of ganglia and neurons in the myenteric plexus of familial dysautonomia patients.

BACKGROUND: Familial dysautonomia (FD) is a hereditary disease of the autonomic and sensory nervous system. A prominent manifestation of FD is gastrointestinal dyscoordination, which contributes to the morbidity and mortality in FD. AIM: As the myenteric plexus is an essential factor in gastrointestinal motility control, we compared its morphology in appendices of FD patients and controls. METHODS: Appendices from FD patients (N=19) were obtained during surgery of fundoplication and gastrostomy; normal appendices (N=17) were obtained from patients suspected to suffer from acute appendicitis, in whom, however, the appendix was found to be normal. Specimens were stained histochemically for NADPH diaphorase (NADPH-d) and in a blinded manner examined under a light microscope for seven morphologic parameters: ganglionic density, neuronal density, ganglionic area, number of stained neurons per ganglion, nerve bundle width, ratio between nervous tissue area and total area, and neuronal area. RESULTS: Ganglionic density was 10.13 per mm(2) in controls versus 5.01 per mm(2) in FD (p<0.05). Neuronal density was 70.12 per mm(2) in controls, compared with 22.09 per mm(2) in FD (p<0.01). The other parameters were not different between the two groups. CONCLUSION: Densities of myenteric ganglia and neurons of FD patients were significantly lower than in controls. This deficiency may contribute to the pathogenesis of FD gastroenteropathy.

Adolescent↗

Mu and kappa opioid receptor modulation of 5-HT3 and NK-3 receptor-evoked release of acetylcholine from the guinea-pig ileum myenteric plexus.

The effects of three different opioid agonists on contractions and [3H]-acetylcholine (ACh) release evoked by 5-hydroxytryptamine3 (5-HT3) and neurokinin-3 (NK-3) receptor activation were examined in the guinea-pig ileum longitudinal muscle-myenteric plexus strip (LMMP) preparation. The selective mu (mu)-opioid receptor agonist (D-Ala2,NMe-Phe4,Gly-ol]-enkephalin (DAMGO; 1 nM-100 nM) and the selective kappa (kappa)-opioid receptor agonist U50488 (10 nM-1 microM) inhibited contractile responses to 5-HT and to the selective NK-3 receptor agonist senktide, producing a concentration-related progressive flattening of their concentration-response curves. IC50 estimates for DAMGO and U50488 were somewhat higher for inhibition of 5-HT-evoked as compared to senktide-evoked contractions, and overall lay in the range 6 nM-51 nM. The selective delta (delta)-opioid receptor agonist [D-Pen2,5]-enkephalin (DPDPE) inhibited contractile responses only at the highest concentration used (1 microM). 3H-overflow from LMMP preparations preincubated with [3H]-choline was measured as an indicator of [3H]-ACh release. DAMGO (1 nM-100 nM) and U50488 (10 nM-1 microM) inhibited the increases in release of [3H]-ACh evoked by 5-HT (10 microM) and by senktide (10 nM) in a concentration-dependent manner. IC50 estimates for DAMGO and U50488 were not significantly different for inhibition of 5-HT as compared to senktide-evoked increases in [3H]-ACh release and lay in the range 6 nM-23 nM. DPDPE again only inhibited these responses at the maximum concentration used (1 microM).(ABSTRACT TRUNCATED AT 250 WORDS)

3,4-Dichloro-N-methyl-N-(2-(1-pyrrolidinyl)-cycloh↗

Enteric glial cells are major contributors to formation of cyclic AMP in myenteric plexus cultures from adult guinea-pig small intestine.

Cultures derived from ganglia isolated from the small intestine of adult guinea-pigs were used to determine relative contribution of neurons and glial cells to stimulation of cAMP formation by forskolin in myenteric ganglia. In untreated cultures (8-12 days), the ratio of glial cells to neurons was 5-fold higher than the ratio in intact myenteric plexus preparations. Treatment with cytosine arabinoside virtually eliminated the glia by the 12th day. Microelectrode recording of excitatory responses to forskolin in AH/Type 2 neurons confirmed the viability of cultured neurons in cytosine arabinoside. Forskolin elevated the cAMP content of cultures and cytosine arabinoside reduced this effect by 80-90%. This suggests that enteric glial cells are the major contributors to cAMP formation in the cultures and that glial cells contribute significantly to elevation of cAMP levels seen in intact myenteric ganglia.

Animals↗

Primary myenteric plexus alterations as a cause of megacolon in Von Recklinghausen's disease.

This is a case report of a megacolon in a 26 years old male patient having typical von Recklinghausen's disease. Exploratory laparotomy shows no neurofibroma on digestive tract. Myenteric plexus study of colic resection specimen following B. Smith technique reveals marked alterations. These alterations are both quantitative (hyperhypoganglionosis) and qualitative (ganglion cells are irregular in shape and size, dendritic processes are hypertrophic, irregular; schwannosis; no inflammatory infiltration). The patient suffers no more transit disorders after adequate resection of this megacolon.

Adult↗

Specific, selective, and complete staining of neurons of the myenteric plexus, using cuprolinic blue.

Wholemounts consisting of both muscular layers of the rat's intestine have been stained with Cuprolinic blue and magnesium chloride. The procedure, which is specific for RNA, gives selective coloration of the somata of the neurons of the myenteric plexus. The neuronal nucleoli and Nissl substance are the only blue structures in such preparations. For descriptive and quantitative work, Cuprolinic blue is more selective than other cationic dyes, and it colors more neurons than can be shown by staining for mitochondrial NADH diaphorase. The absence of background color enables neurons to be identified more confidently and counted more quickly than is possible with other techniques, in which nuclei or mitochondria in smooth muscle and neuroglial cells are also stained. Numbers of myenteric neurons determined using the new method are higher than those obtained by other means.

Animals↗

Morphological and quantitative study of the myenteric plexus of the ascending colon of rats subjected to proteic desnutrition.

We carried out this study with the purpose of contributing on the effects of the proteic desnutrition on the morphological aspects and quantitative analysis of the neurons in the myenteric plexus of the ascending colon of adult Rattus norvegicus. Twenty adult rats were divided into two groups: in one of them, we offered a normal ration with proteic level of 22% (control group) and in the other, a ration with a proteic level of 8% (experiment group) during 120 days. We did the whole-mount preparations for the ascending colon and stained them with the Giemsa technique and the histochemical technique of NADH-diaphorase. The rats with proteic desnutrition showed a body weight, on average, to be 35.1% less than those of the control group, and the colon was on average, 26.8% shorter and 6.7% narrower. Thus, it was to be expected that the colon of animals with proteic desnutrition had a neuronal density 31.62% greater than the rats of the control group. Nevertheless, the difference with the Giemsa technique was on average 18.4%, demonstrating a mean neuronal loss of 13.25%.

Animals↗

Pattern of distribution and co-localization of NOS and ATP in the myenteric plexus of human fetal stomach and intestine.

The pattern of distribution and co-localization of nitric oxide synthase (NOS) and quinacrine fluorescence (indicative of vesicular adenosine 5'-triphosphate, ATP), and co-localization of NADPH-diaphorase (NADPH-d) activity and NOS-immunoreactivity in the myenteric plexus of pre-term human fetal (6-17 weeks of gestation) stomach and small intestine was examined using immunohistochemical and histochemical techniques. In all stages of gestation investigated, NOS-immunoreactive and NADPH-d-reactive myenteric neurons and nerve fibres were seen in the fetal intestine and stomach. However, in fetuses of 6-10 weeks of gestation, only 15% of the NADPH-d-positive myenteric neurons were NOS-immunoreactive, whereas a 100% co-localization was found in samples of 12-17 weeks of gestation. Quinacrine fluorescent myenteric neurons and nerve fibres were found only in the fetal intestine of 12-17 weeks of gestation, of which 25% of the NADPH-d-positive myenteric neurons in these samples were quinacrine fluorescent. These findings demonstrate the presence and co-localization of markers for nitric oxide (NO)- and ATP-utilizing myenteric neurons and nerve fibres in the early stages of gestation, suggesting possible co-transmitter and/or trophic roles of ATP and NO in the process of development and maturity of human myenteric neurons. In addition, the fact that only a small percentage of NADPH-d-reactive myenteric neurons express NOS immunoreactivity at 6-10 weeks of gestation confirms that NADPH-d-reactivity does not always represent NOS activity.

Adenosine Triphosphate↗

ATP and nitric oxide: inhibitory NANC neurotransmitters in the longitudinal muscle-myenteric plexus preparation of the rat ileum.

1. The nature of neurotransmitter(s) involved in non-adrenergic non-cholinergic (NANC) relaxations induced by electrical stimulation (10 s trains, 1-8 Hz) was investigated in the precontracted longitudinal muscle-myenteric plexus preparation of the rat ileum. 2. Electrical stimulation of the tissue induced complex responses, consisting of a primary contraction, a primary relaxation, an off-relaxation and a rebound contraction, which were all tetrodotoxin(TTX)-sensitive. 3. Vasoactive intestinal polypeptide (VIP) and carbon monoxide (CO) did not induce relaxations. alpha-Chymotrypsin did not reduce the relaxations induced by electrical stimulation, while zinc protoporphyrin IX had non-specific effects. 4. Nitric oxide (NO) induced concentration-dependent relaxations. NG-nitro-L-arginine methylester (L-NAME) abolished the primary contractions and off-relaxations, while it partially reduced the primary relaxations. 5. ATP induced relaxations and ATP-desensitization of the tissues partially reduced the primary relaxations. Suramin and reactive blue 2 did not consistently influence the primary relaxations. 6. The ATP-induced relaxations were not influenced by L-NAME or TTX. The inhibitory effect of ATP-desensitization and L-NAME did not summate. 7. The cyclic AMP content of the tissue did not increase upon electrical stimulation or after addition of NO or ATP. The cyclic GMP content of the tissue increased upon electrical stimulation and addition of NO, but not after addition of ATP. 8. It is concluded that the relaxation induced by electrical stimulation consists of two types of responses. The off-relaxation is completely nitrergic, while the primary relaxation is mediated by NO, ATP and an as yet unknown transmitter which is not VIP or CO.

Adenosine Triphosphate↗

Direct evidence for a release of acetylcholine from the myenteric plexus of guinea pig small intestine by substance P.

Myenteric plexus-longitudinal muscle strips from guinea pig small intestine were labeled with [3H]choline while under continuous field stimulation. Release of newly synthesized [3H]acetylcholine was studied in the presence of substance P afterwards. Substance P evoked release of [3H]acetylcholine in a dose-related fashion. Both tetrodotoxin and [D-Pro2,D-Phe7,D-Trp9]substance P, a synthetic antagonist of substance P, completely blocked this release and provided evidence for a cholinergically mediated mechanism of substance P on enteric neurons.

Acetylcholine↗

Megacolon in myotonic dystrophy caused by a degenerative neuropathy of the myenteric plexus.

A 32-yr-old man with myotonic dystrophy had a left hemicolectomy performed because of a megacolon. The colonic mucosa, smooth muscle, and connective tissue appeared normal by hematoxylin and eosin and trichrome stains and transmission electron microscopy. In contrast, the myenteric plexus had markedly fewer neurons than normal on the hematoxylin and eosin stains. Silver staining of the plexus revealed degeneration and decreased numbers of argyrophilic neurons, which were smaller and had fewer processes and a more uneven staining quality than controls. Many axons were fragmented, and increased numbers of glial cell nuclei were present in the plexus. Degenerative changes in the neurons were present in a patchy distribution on transmission electron microscopy. Immunohistochemistry revealed a decrease of the substance P- and enkephalin-immunoreactive fibers in the muscularis externa. This suggests that colonic motor dysfunction associated with myotonic dystrophy may be caused by a visceral neuropathy that involves the substance P- and enkephalin-immunoreactive fibers of the smooth muscle.

Adult↗

beta-Endorphin is contained within presumptive receptosomes and lysosomes of the myenteric plexus of the rat.

Using the microdissection technique combined with the pre-embedding immunostaining method, beta-endorphin immunoreactivity (beta-END-IR) was noted within ring-shaped elements lying singly or in groups in nerve processes of the duodenal myenteric plexus of the rat. The beta-END-IR was noted as a strongly electron-dense precipitate rim on the inner surface of these elements. The membrane of the ring-shaped element as well as the beta-END precipitate rim were strikingly often unilaterally interrupted at the same site. Some of the ring-shaped beta-END-positive elements were noted within large osmiophilic bodies. The beta-END immunoreactive ring structure was 60-300 nm in diameter and possessed an empty electron-lucent space as well as a thin electron-dense membrane. The osmiophilic bodies were pleormorph, had a mean diameter of 250 nm and revealed thick electron-opaque membranes. Their inner spaces were homogenously filled with electron-dense materials. These findings might indicate that the beta-END-IR-containing ring-shaped elements represent receptosomes and that the pleomorph osmiophilic bodies are identical to lysosomes.

Animals↗

gamma-Aminobutyric acid action in guinea-pig ileal myenteric plexus.

The responses of the guinea-pig ileum myenteric plexus-longitudinal muscle preparation to gamma-aminobutyric acid (GABA) and several analogs were examined in direct and electrically stimulated preparations. GABA, muscimol and 3-aminopropane sulfonic acid (3-APS), but not baclofen, produced a transient, concentration-dependent contraction followed by relaxation. These responses were antagonized by atropine, tetrodotoxin, bicuculline methiodide and picrotoxin. Responses to GABA and 3-APS exhibited a marked tachyphylaxis. GABA and baclofen, but not muscimol or 3-APS, exerted a relaxant effect on contractions induced by supramaximal field stimulation in the longitudinal muscle. These responses were insensitive to bicuculline, bicuculline methiodide and picrotoxin, and were unaffected by other pharmacological agents including adrenergic, cholinergic and histamine antagonists. The results suggest that GABA and its analogs act at a population of excitatory receptors mediating the release of acetylcholine from enteric neurons, and at a population of inhibitory receptors which inhibit the stimulated release of acetylcholine.

Amino Acids↗

Stimulation of myenteric plexus neurite outgrowth by insulin and insulin-like growth factors I and II.

A defined culture medium containing insulin, insulin-like growth factor I (IGF-I) or insulin-like growth factor II (IGF-II) supported morphological development of myenteric plexus neurons derived from neonatal guinea pigs. Insulin increased neurite outgrowth 3-fold at concentrations as low as 0.2 nM. Similar significant and dose-dependent increases in neurite outgrowth were noted with IGF-I and IGF-II. Stimulation of neurite outgrowth was abolished by exposure to cytosine arabinofuranoside, an agent toxic to non-neuronal cells, implying that trophic effects of insulin or insulin-like growth factors require the presence of non-neuronal elements in culture.

Animals↗

Pharmacological analysis of [3H]-senktide binding to NK3 tachykinin receptors in guinea-pig ileum longitudinal muscle-myenteric plexus and cerebral cortex membranes.

1. The binding properties and pharmacological specificity of the selective NK3 tachykinin receptor agonist [3H))-senktide [( 3H]-succinyl[Asp6,MePhe8] substance P (6-11] have been examined in homogenates of guinea-pig ileum longitudinal muscle-myenteric plexus (LM/MP) and cerebral cortex. 2. Scatchard analysis of saturation binding studies in guinea-pig ileum LM/MP and cerebral cortex membranes indicated that [3H]-senktide bound to a single site with apparent high affinity, KD = 2.21 +/- 0.65 nM; Bmax = 13.49 +/- 0.04 fmol mg-1 protein in ileum and KD = 8.52 +/- 0.45 nM; Bmax = 76.3 +/- 1.6 fmol mg-1 protein in cortex (values are means +/- ranges; n = 2). 3. The pharmacological profile for tachykinins and analogues in displacing [3H]-senktide from ileum membranes was: [MePhe7] neurokinin B greater than neurokinin B (NKB) congruent to senktide greater than eledoisin greater than substance P (SP) greater than neurokinin A(NKA) greater than physalaemin greater than [Sar9,Met(O2)11]SP greater than [Nle10]NKA(4-10) = [Glp6,L-Pro9]-SP(6-11) greater than substance P methyl ester, consistent with [3H]-senktide binding to an NK3 subtype of tachykinin receptor. A similar rank order of affinity was obtained for these peptides in displacing [3H]-senktide from cortex membranes. 4. Several tachykinin receptor agonists were tested for their ability to displace [3H]-senktide from ileal and cortical NK3 binding sites and were found to be either weak displacers (pIC50 less than 5.00) or inactive. 5. The binding of [3H]-senktide to cortex membranes was inhibited by GTP (p1C,0 = 6.49)and GTP-gamma- S (p1C,0 = 6.67) with ATP being at least three orders of magnitude less potent (pIC50 = 3.55). 6. These results indicate that both central and peripheral NK3 receptors share a similar pharmacological specificity and that they may be labelled selectively with the NK3 receptor agonist [3H]-senktide.

Animals↗

The effects of atropine on [3H]acetylcholine secretion from guinea-pig myenteric plexus evoked electrically or by high potassium.

1. The myenteric plexus-longitudinal muscle preparation of the guinea-pig ileum was incubated with [(3)H]choline (1.125-1.5 muM), and then superfused with Tyrode solution containing hemicholinium-3 (10 muM). Secretion of [(3)H]acetylcholine ([(3)H]ACh) was evoked either (a) by electrical field stimulation (0.5-15 Hz, 150 shocks per period, 0.5 msec), used to ;indirectly' depolarize the varicosities of nerve terminals, or (b) by high potassium (40 mM with 1 muM-tetrodotoxin, for 6 min, or 80 mM without tetrodotoxin, for 1 min), to ;directly' depolarize varicosities.2. With these stimulation parameters, which yielded about the same fractional secretion of [(3)H]ACh, and with eserine (10 muM) present in the medium, atropine (1 muM) enhanced the ;indirectly', electrically evoked secretion 3.65+/-0.34 (n = 6) fold, and that caused by 40 mM or 80 mM-potassium 1.82+/-0.06 (n = 6) or 1.55+/-0.09 (n = 10) fold, respectively. Atropine thus enhanced ;indirectly', electrically evoked secretion 4-fold more than that caused by ;direct' depolarization of varicosities with high potassium (P < 0.001).3. This difference is not likely to be caused by depression of the sensitivity of the presynaptic muscarinic receptors to ACh released by nerve stimulation, caused by the hypertonicity of the medium in the potassium stimulation experiments. The medium made hypertonic by addition of Tris-HEPES (80 mM) did lower the binding affinity of membrane preparations of (pre- and post-synaptic) muscarinic receptors, to carbamylcholine, and also the contractile responsiveness of the longitudinal muscle to this agent, in both cases to about one half. But it did not appear to alter the responsiveness of either pre- or post-synaptic muscarinic receptors to endogenous ACh, released by nerve stimulation.4. The results support a dual-mode model for the muscarinic negative feed-back control of ACh secretion from the nerve terminals of this preparation, mainly operating by restriction of the invasion of terminals, and only secondarily by depression of the efficiency of depolarization-secretion coupling in invaded varicosities.5. Since this model has earlier been proposed to apply for the control of secretion of [(3)H]noradrenaline from the micro-anatomically similar nerve terminals of noradrenergic nerves, the present findings suggest that the model may have a wider biological significance, and possibly apply to the control of the secretory activity of boutons-en-passant nerve terminals in general.

Acetylcholine↗

Demonstration of myenteric plexus abnormalities in genetic diseases by a microdissection technique: preliminary studies.

Eighty-eight specimens of esophagus, small intestine, or colon from 45 patients, predominantly infants and children, with 30 different genetic diseases were analyzed by a microdissection technique for the following abnormalities of the Auerbach (myenteric) plexus: (1) abnormality of the pattern of the nervous network of the plexus, (2) abnormal fraction of neural tissue in the plane of the plexus, (3) abnormal size or appearance of the cytoplasm of the neurons of the plexus, and (4) abnormal number of neurons in the ganglia of the plexus. Seven of 8 specimens of esophagus from patients with neuronal storage diseases (infantile Niemann-Pick disease, Jansky-Bielschowsky disease, etc.) showed an increased fraction of neural tissue in the plane of the plexus, whereas 2 of 3 patients with Cockayne syndrome showed a reduced fraction, with abnormally slender interganglionic fibers. The fraction of neural tissue in the plane of the plexus was also abnormal at one or more levels in patients with adrenoleukodystrophy, ataxia telangiectasia, Krabbe disease, and juvenile metachromatic leukodystrophy. Abnormality of neuron size and cytology was seen in several neuronal lipidoses, including Jansky-Bielschowsky and Sandhoff diseases and juvenile GM2 gangliosidosis, with the most striking neuronal enlargement noted in infantile Niemann-Pick disease. Abnormalities of plexus mass or pattern, as well as those of neuronal cytoplasm and neuron number, offer improved insight into possible mechanisms producing gastrointestinal tract dysfunction (swallowing difficulty, gastroesophageal reflux, constipation, etc) in patients with genetic disorders.

Child↗

Neurons dissociated from rat myenteric plexus retain differentiated properties when grown in cell culture. II. Electrophysiological properties and responses to neurotransmitter candidates.

We have used intracellular recordings to study the electrophysiological and pharmacological properties of neurons that have been grown in cell cultures after having been dissociated from the myenteric plexus of the small intestine of newborn rats. Studies of action potential mechanisms revealed that all of the neurons could generate Na+-dependent action potentials in the presence of Ca2+-channel blockers and that about 70% could generate Ca2+-dependent action potentials when Na+ channels were blocked with tetrodotoxin. No neurons generated long afterhyperpolarizations after single action potentials but about 50% of neurons did so following trains of action potentials. Over 95% of the neurons tested accommodated rapidly to sustained depolarization. The effects of several enteric neurotransmitter candidates were studied by superfusing or pressure-ejecting test solutions while recording neuronal responses. All of the cultured neurons tested had nicotinic responses to acetylcholine. Subsets of neurons responded to muscarinic cholinergic agonists (slow depolarization and increased excitability), serotonin (fast depolarization or slow depolarization and increased excitability), gamma-aminobutyrate (fast depolarization), substance P (slow depolarization, biphasic fast and slow depolarization or increased excitability without a change in membrane potential), vasoactive intestinal peptide (slow depolarization and increased excitability), or [Met]enkephalin (slow hyperpolarization and/or decreased action potential duration). We conclude that myenteric neurons grown in cell culture retain many of the physiological and pharmacological properties that they have in situ. Such cultures will permit detailed biophysical and pharmacological studies of the mechanisms of action of enteric neurotransmitter candidates.

Acetylcholine↗

A further analysis of the contraction induced by activation of cholecystokinin A receptors in guinea pig isolated ileum longitudinal muscle-myenteric plexus.

The activity of a selective cholecystokinin (CCK)-A receptor agonist, N-acetyl derivative of A71623 (Ac-Trp-Lys(epsilon-N-[2-methylphenylamino-carbonyl]) -Asp-(NMe)Phe-NH2) was investigated in the guinea pig isolated ileum longitudinal muscle myenteric plexus. NAA caused both a phasic and tonic contraction at all concentrations tested (1-1000 nM). The selective CCK-A antagonist L-364,718 (Devazepide) antagonized both types of contraction with a pKB of 10.10 and 9.95, respectively. The CCK-B selective antagonist L-365,260 ((3R(+)-2,3-dihydro-1-methyl-2-oxo-5-phenyl-1H-1, 4-benzodiazepine-3yl)-N-(3-methylphenyl)-urea) was inactive up to a concentration of 30 nM. Atropine at 300 nM and 1000 nM reduced the maximal response of NAA by only 17% and 50%, respectively. The selective neurokinin (NK)-1 antagonists GR 82334 ([D-pro9[Spiro-gamma-Lactam] Leu10, Trp11]-Phys (1-11)9) at 300 and 1000 nM and (+-) CP-96,345 [(2S, 3S)-cis- 2-(diphenylmethyl)-N- [(2-methoxyphenyl)-methyl] -1-azabici-clo [2.2.2]octan-3-amine] at 10 nM were inactive or partially active. When atropine and GR 82334 or (+/-) CP-96,345 were combined, they produced a dose-dependent synergistic inhibition of both phasic and tonic contractions induced by NAA. The selective NK-3 receptor agonist senktide induced both phasic and tonic contractions that were blocked by tetrodotoxin. In the presence of atropine and GR 82334, both 300 nM, a synergistic depression of the response to senktide similar to that observed for the agonist NAA was disclosed.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗