Cholinesterases and choline acetyltransferase in the longitudinal muscle of the guinea pig ileum

Pharmacological mechanism responsible for the Atractylodes japonica-induced distal colonic contraction in rats

BACKGROUND AND AIM

Atractylodes japonica Koidz (Compositae) has been commonly used to treat the gastrointestinal (GI) disorders in Korean traditional medicine, but its pharmacological roles in the regulation of GI motility have not been clarified yet.

METHODS

Atractylodes japonica was sequentially partitioned with MeOH, n-hexane, CHCl(3), EtOAc and n-BuOH saturated with H(2)O, and the effects of Atractylodes japonica extracts on the spontaneous contractility of GI muscle strips prepared from rats were measured.

RESULTS

Among five different fractionations, EtOAc extracts of Atractylodes japonica (AJEA) dose-dependently increased the low frequency contraction of distal colon longitudinal muscles (DCLM), and the ED(50) values were revealed to be 1.71×10(-9) g/ml. Among GI tracts, a prominent contractile response to AJEA was observed only in the DCLM. The contractile patterns produced by AJEA remarkably differed from those caused by acetylcholine and 5-HT. 4-DAMP and methoctramine at 0.5 μM significantly blocked the AJEA (1.0 μg/ml)-induced contraction of DCLM, but ondansetron, GR113808 and methysergide at 1.0 μM in combination did not change the AJEA-induced DCLM contractions. Acetylethylcholine mustard (5.0 μM) significantly diminished the AJEA-induced DCLM contractions, whereas p-chlorophenyl alanine (1.0 μM) did not affect the stimulatory effects of AJEA on the DCLM contractions.

CONCLUSION

The present results suggest that AJEA may specifically act on the DCLM among GI smooth muscles, and AJEA-induced DCLM contraction is likely mediated, at least, by activation of ChAT and acetylcholinergic muscarinic receptors.

Structural abnormalities associated with congenital megacolon in transgenic mice that overexpress the Hoxa-4 gene

Congenital megacolon develops in transgenic mice that overexpress the homeobox-containing gene, Hoxa-4. The current study was done to identify abnormalities of the terminal colon that might account for the phenotype. The terminal bowel of transgenic mice was compared with that of control and lethal spotted (ls/ls) mice, a strain in which megacolon also develops. The terminal colon of the transgenic mice contained fewer ganglia than that of controls, but was hypoganglionic, rather than aganglionic like that of ls/ls mice. The neurons present in the adult transgenic colon were significantly increased in size and a subset of very large neurons (> 40 microns in maximum diameter) were observed. Electron microscopic studies of young adult transgenic mice revealed that the ganglia and nerves of the myenteric plexus had the ultrastructure of extraenteric peripheral nerve rather than that of the enteric nervous system (ENS). The myenteric ganglia in the transgenic animals contained Schwann cells associated with a basal lamina that enveloped axons completely and individually, instead of glia. Although collagen is excluded from the ganglia and thin nerve fibers of the normal ENS, a collagen-containing endoneurium surrounded each of the axon-Schwann cell units of the abnormal nerve fibers of the transgenic colon. Some of the neurons of the transgenic mice were located in these nerve bundles rather than in ganglia. There were also smooth muscle abnormalities in the terminal bowel of the transgenic mice. Wide gaps were present in the longitudinal muscle of the transgenic mice; these gaps contained ganglia that were in contact with the adventitia. These longitudinal smooth muscle cells were more irregular than those of controls and they contained fewer puncta adherens; moreover, a larger proportion of the volume of the cytoplasm of transgenic smooth muscle cells was occupied by organelles. Finally, an extensive thickening and reduplication of the basal lamina surrounding the smooth muscle cells of the muscularis mucosa was observed in the transgenic colon and resembled that found in ls/ls mice. These data suggest that both smooth muscle and the innervation of the terminal bowel of neonatal Hoxa-4 transgenic mice are structurally abnormal. Although some of the abnormalities seen in Hoxa-4 transgenic mice are similar to those which arise in ls/ls mice, the two conditions are not identical. In both animals, the data are consistent with the hypothesis that the defects arise as a result of a defective interaction between the precursors of enteric neurons and smooth muscle.

Transmitter diversity in ganglion cells of the guinea pig gallbladder: an immunohistochemical study

Several neurotransmitters have been reported to exist in the ganglionated plexus of the guinea pig gallbladder. These include substance P, neuropeptide Y (NPY), calcitonin gene-related peptide, vasoactive intestinal peptide (VIP), acetylcholine, norepinephrine, serotonin, and dopamine. To determine which neuropeptides are intrinsic to gallbladder ganglia, we performed immunohistochemistry on colchicine-treated preparations. In separate, single-labeled preparations, a majority of neurons contained substance P-, NPY-, or somatostatin-like immunoreactivity. In double-labeled preparations, a large majority of the neurons that contained substance P-like immunoreactivity also contained NPY-like immunoreactivity and somatostatin-like immunoreactivity. Immunoreactivity for VIP was present in a small percentage of the gallbladder neurons which did not contain substance P-like immunoreactivity. Additional experiments were done to test for the presence of other compounds, known to exist in the neurons of the gut. Although immunoreactivity was found in control preparations of small intestine, the ganglionated plexus of the gallbladder lacked immunoreactivity for galanin, dynorphin, enkephalin, gastrin-releasing peptide, or gamma-aminobutyric acid. We conclude that ganglia of the guinea pig gallbladder contain at least two populations of neurons, based on transmitter phenotype. One of these populations appears to contain substance P, NPY, and somatostatin. Another population, which represents a small contingent of the total population of neurons, contains VIP.

Structure, afferent innervation, and transmitter content of ganglia of the guinea pig gallbladder: relationship to the enteric nervous system

Although a well-developed plexus of nerves and ganglia is known to be present in the wall of the gallbladder, little has previously been learned about the function or organization of this innervation. The current study was undertaken in order to evaluate the hypothesis that the ganglionated plexus of the gallbladder is analogous to elements of the enteric nervous system (ENS). The ganglionated plexus of the gallbladder was found to resemble closely the submucosal plexus of the small intestine in its organization into two irregular anastomosing and interwoven networks of ganglia, in the numbers of neurons per ganglion, and in the manifestation of histochemically demonstrable acetylcholinesterase activity in virtually all ganglion cells. In common with enteric ganglia, laminin immunoreactivity was observed to be excluded from the interiors of gallbladder ganglia, which were surrounded by a periganglionic laminin-immunoreactive sheath. As in the submucosal plexus, intrinsic substance P-, vasoactive intestinal polypeptide (VIP)-, and neuropeptide Y (NPY)-immunoreactive neurons were seen in the ganglionated plexus of the gallbladder. Extrinsic nerves in the gallbladder that degenerated following chemical sympathectomy with 6-hydroxydopamine (6-OHDA), and which contained NPY, tyrosine hydroxylase (TH), and dopamine-beta-hydroxylase (DBH) immunoreactivities, formed a perivascular plexus closely associated with blood vessels. Endogenous catecholamines could also be demonstrated in these perivascular nerves by aldehyde-induced histofluorescence. In addition to perivascular nerves, paravascular nerve bundles were observed that were loosely associated with vessels, did not degenerate following administration of 6-OHDA, and contained NPY immunoreactivity. Other paravascular nerves, probably visceral sensory axons, coexpressed substance P and calcitonin-gene-related peptide (CGRP) immunoreactivities. The ganglionated plexus of the gallbladder resembled enteric ganglia in having intrinsic 5-hydroxytryptamine (5-HT)-immunoreactive cells and highly varicose nerve fibers. The 5-HT-immunoreactive gallbladder axons were, like those of the gut, resistant to 6-OHDA, and separate from fibers that expressed TH immunoreactivity. Differences between the ganglionated plexus of the gallbladder and enteric ganglia of the small intestine included in the gallbladder are 1) the presence of TH-immunoreactive cells that contain an endogenous catecholamine, but not DBH; 2) DBH-immunoreactive neurons, some of which coexpress substance P immunoreactivity, but which contain neither a catecholamine nor TH immunoreactivity; 3) an apparent absence of CGRP-immunoreactive cell bodies.(ABSTRACT TRUNCATED AT 400 WORDS)

Origin and morphology of nerve fibers in the aganglionic colon of the lethal spotted (ls/ls) mutant mouse

The lethal spotted mutant mouse (ls/ls) develops congenital megacolon because of the absence of ganglia in the terminal colon. This aganglionosis results from a failure of neural crest cells to colonize this area during fetal life. We have postulated that the microenvironment of the aganglionic segment of bowel is abnormal. Our hypothesis suggests that this abnormal enteric microenvironment fosters the sprouting of neuritic processes. We further propose that neural and glial precursors cease to migrate once they have extended their definitive processes. As a result, the area distal to the site where neurite extension is favored does not become colonized by neural or glial precursors. A prediction of this hypothesis is that the aganglionic tissue should be innervated by axons from neurons located both in the more proximal ganglionated bowel and in ganglia located outside the gut. Neurons and their processes in control and ls/ls terminal gut were located by the histochemical demonstration of acetylcholinesterase (AChE) activity and their structure was classified as intrinsic (enteric) or extrinsic in type by electron microscopy. In ls/ls mice the submucosal plexus was much more severely affected than the myenteric plexus. No submucosal ganglia were found within 30 mm of the anus. In contrast, myenteric ganglia extended to within 4 mm of the anus on the mesenteric side of the gut and to within 15 mm on the antimesenteric side. Rostral to the areas that were absolutely aganglionic, both plexuses were hypoganglionic, especially the submucosal plexus, which was hypoganglionic throughout the entire colon. Both the aganglionic and caudal hypoganglionic zones of the ls/ls bowel were penetrated by large nerve trunks that had the ultrastructural characteristics of extra-enteric peripheral nerve. Unusual ganglia, outside the enteric musculature in the adventitia of the colon, were connected to these trunks. The location of the cell bodies of origin of the nerve fibers in the terminal colon of control mice and in the aganglionic segment of the bowel in ls/ls mice was determined by following the retrograde transport of tracers injected as close as possible to the anus. An extrinsic innervation originating from the inferior mesenteric ganglion and dorsal root ganglia (L6-S1) was found in both types of animal. In control but not ls/ls mice retrograde labeling was also observed in the sacral parasympathetic nucleus of the spinal cord. In addition, neuritic processes were traced to neurons in myenteric ganglia. In control mice, these labeled neurons were present in ganglia within the injection site as well as in bowel rostral and caudal to it.(ABSTRACT TRUNCATED AT 400 WORDS)

Lymph heart musculature in birds

Development and innervation of the lymph heart musculature of chicken, emu, rhea, and duck was studied by electron microscopy at post-hatch ages from 3 days to adulthood. Development of innervation was monitored by acetylcholinesterase staining. Horseradish peroxidase was used to determine the extent of the transverse tubule network. Chickens were unusual among these birds in that lymph heart myocytes had already undergone a definitive differentiation and degeneration by 3 days. In ducks and ratite birds, lymph heart myocytes more slowly but progressively differentiate a cytomorphology that does not conform in all characteristics to cardiac or skeletal muscle and even resembles in some aspects, smooth muscle. Myofibrils become the dominant cytoplasmic structure, transverse tubules form "internal couplings" with agranular reticulum cisternae, and "external couplings" are formed between myocytes at myomyal junctions. The myomyal junctions also contain AChE-positive reaction product and some subplasmalemmal vesicles that lack a dense core. The lymph heart myocardium of ducks of 2 weeks demonstrated mitotic figures. In adult ducks the myosatellite cell numbers diminish and a characteristic pattern of myocyte degeneration appears. In juvenile ducks and ratites some myocytes differentiate to conductile cells, much as the conductile myocytes and myofibers of the blood heart. The lymph heart innervation is described, and the role of nerve in differentiation and maintenance of myocyte morphology in the lymph heart is discussed.

Ultrastructural localization of cholinesterase during chondrogenesis and myogenesis in the chick limb bud

Cholinesterase (ChE) is transiently expressed in undifferentiated embryonic cells. In the chick limb bud ChE-activity was found in the apical ectodermal ridge and in the subridge mesenchyme. The reaction was localized in the perinuclear cisterna, in an extensive network of narrow profiles of endoplasmic reticulum (ER), and in the Golgi complex. The chondroblasts emerging from the subridge mesenchyme, also showed strong ChE-activity. During differentiation the enzyme first disappeared from the Golgi zone. Then, the narrow ChE-positive ER was successively replaced by ChE-negative extended rough ER characteristic for the differentiated chondrocyte. The myoblasts showed weak ChE-activity with the same ultrastructural localization as in other mesenchymal cells. After fusion the myotubes exhibited strong ChE-activity in the perinuclear cisterna and the developing sarcoplasmic reticulum. In later stages of myogenesis the myoblasts were closely attached to the myotubes and had lost their ChE-activity. During mitosis of ChE-positive cells, ChE-activity was retained in fragments of perinuclear cisterna and ER. In ChE-active mesenchymal cells and chondroblasts we observed specialized contact zones between ER and plasma membrane. ChE-active cisternae of ER run parallel to the plasma membrane with a gap of approximately 10-15 nm. We discuss a possible function of a cholinergic system during morphogenesis.

Acetylcholinesterase and choline acetyltransferase staining of neurons in the opossum esophagus

The purpose of the present investigation was to identify and compare cholinergic intramural neurons in the lower esophageal sphincter and esophageal body by histochemical staining for acetylcholinesterase and the enzyme that synthesizes acetylcholine, choline acetyltransferase. Opossums were anesthetized and their abdominal cavity was opened by a midline incision to expose the esophagogastric junction. The lower esophageal sphincter was identified manometerically and localized in situ with markers. Tissues were removed, rapidly frozen in freon cooled with liquid nitrogen and serial cryostat sections were obtained from the lower esophageal sphincter and esophageal body. Sections were stained with one of the above histochemical procedures and adjacent sections were stained with Solachrome cyanin , which differentially stains nerve elements from muscle fibers. The muscle of the lower esophageal sphincter and esophageal body was stained with nonspecific cholinesterase with some selectivity of intensity of reaction in the various smooth muscle layers. All identifiable plexus neurons in the esophagus stained for nonspecific cholinesterase and acetylcholinesterase. Nerve fiber tracts were also stained for acetylcholinesterase within the longitudinal and circular layers of the tunica muscularis. Reaction for choline acetyltransferase showed no staining in the muscle layers or nerve fiber tracts of either part of the esophagus studied; however, selected neurons within the myenteric plexus of both regions (approximately 38%) were reactive. There was no significant difference in the number of positive choline acetyltransferase neurons in the lower esophageal sphincter or esophageal body.

Cholinesterases and choline acetyltransferase in the ductus deferens of the guinea-pig

Several authors have reported that longitudinal and circular muscle layers of the guinea-pig ductus deferens possess a rich adrenergic innervation. Cholinergic innervation has been doubted by several authors, especially its presence in the longitudinal muscle layer. Acetylcholinesterase and butyrylcholinesterase were demonstrated, by electron-microscopic examination of both muscle layers of the guinea-pig ductus deferens, to be localized on the axolemma of the nerve endings and in smooth-muscle fibres, on sarcolemma, in the intracellular caveolae and in the intercellular space. Activity of cholinesterases and choline acetyltransferase was measured by the radiometric method and was found in both muscle layers. The activity of butyrylcholinesterase was higher than that of acetylcholinesterases in the homogenates of the whole ductus deferens and in the longitudinal muscle layer. In the circular muscle layer, the activity of acetylcholinesterase was higher than the activity of butyrylcholinesterase. In both muscle layers, we also found choline acetyltransferase, the activity being stronger in the circular layer. The localization of cholinesterases in smooth-muscles in the same places as the calcium and muscarinic acetylcholine receptors is discussed, together with the possibility that the enzyme is in some way involved in the excitation-contraction mechanism of smooth muscle.

Simultaneous ultrastructural localization of serotonin and cholinesterases in Mytilus byssal retractor muscle (A.B.R.M.)

Ultrastructural localization techniques for cholinesterases (ChE) by the Karnovsky method, for monoamines by the technique of Wood, and Tranzer and Richards, and for 5HT by the technique of Wood, were performed on the anterior byssal retractor muscle of Mytilus. Simultaneous ultrastructural localization of 5HT and ChE was obtained by the use of the false neurotransmitter 5,6-DHT, followed by the method of Karnovsky for ChE. The glio-interstitial tissue presents a constant ChE activity, mainly localized on the plasma membrane, even in those processes which accompany tryptaminergic (5HT containing) neurites. Muscle cell membrane also reacts positively to the Karnovsky method. The tryptaminergic neurites themselves do not show any ChE activity; they contain dichromate reactive large (100 nm) dense cored vesicles. The presence of differentiated tryptaminergic neuromuscular junctions, suggested by other authors, is established. It was not possible to distinguish classes of nerve endings by the typology of their vesicular content. It is concluded that one can reasonably plan to study the effect of glial ChE inhibition on the physiology of the tryptaminergic (relaxing) response of the A.B.R.M. to nerve stimulation.

Choline acetyltransferase in the chick limb bud

In embryonic tissues a primitive cholinergic system is transiently expressed during morphogenesis. In the chick limb bud expression of the primitive cholinergic system in mesenchyme and central chondrogenic core precedes the appearance of the definitive cholinergic system in nerve and muscle. Here we show that, parallel to the expression of cholinesterase in mesenchyme and chondroblasts, embryonic cells are capable of acetylcholine synthesis. Choline acetyltransferase (ChAT) activity was measured by the radiometric assay of Fonnum (1975).