The distribution and colocalization of neuropeptides in perivascular nerves innervating the large arteries and veins of the snake,Elaphe obsoleta

Summary Single- and dual-labelling immunohistochemistry were used to determine the distribution and coexistence of neuropeptides in perivascular nerves of the large arteries and veins of the snake, Elaphe obsoleta, using antibodies for vasoactive intestinal polypeptide, substance P, calcitonin gene-related peptide, neuropeptide Y, galanin, somatostatin, and leu-enkephalin. Blood vessels were sampled from four regions along the body of the snake: region 1, arteries and veins anterior to the heart; region 2, central vasculature 5 cm anterior and 10 cm posterior to the heart; region 3, arteries and veins in a 30-cm region posterior to the liver; and region 4, dorsal aorta and renal arteries, renal and intestinal veins, 5–30 cm cephalad of the vent. A moderate to dense distribution of vasoactive intestinal polypeptide-like immunoreactive fibres was found in most arteries and veins of regions 1–3, but fibres were absent from the vessels of region 4. The majority of vasoactive intestinal polypeptide-like immunoreactive fibres contained colocalized substance P-like immunoreactivity, and these fibres were unaffected by either capsaicin or 6-hydroxydopamine (6-OHDA) pretreatment. In the anterior section of the snake, the vagal trunks contained many cell bodies with colocalized vasoactive intestinal polypeptide and substance P-like immunoreactivity. It is suggested that the vasoactive intestinal polypeptide/substance P-like immunoreactive cell bodies and fibres are parasympathetic postganglionic nerves. Neuropeptide Y-like immunoreactive fibres were observed in all arteries and veins, being most dense in regions 3 and 4. The majority of these fibres also contained colocalized galanin-like immunoreactivity, and were absent in tissues from 6-OHDA pretreated snakes, suggesting that neuropeptide Y and galanin are colocalized in adrenergic nerves. A small number of neuropeptide Y-like immunoreactive fibres contained vasoactive intestinal polypeptide but not galanin, and were unaffected by 6-OHDA treatment. All calcitonin gene-related peptide-like immunoreactive fibres contained colocalized substance P-like immunoreactivity, and these fibres were observed in all vessels, being particularly dense in the carotid artery and jugular veins. All calcitonin gene-related peptide/substance P-like immunoreactive fibres appeared damaged after capsaicin treatment suggesting they represent fibres from afferent sensory neurons. A sparse plexus of somatostatin-like immunoreactive fibres was observed in the vessels only from region 4. No enkephalin-like immunoreactive fibres were found in any blood vessels from any region. This study provides morphological evidence to suggest that there is considerable functional specialization within the components of the rat snake peripheral autonomic system controlling the circulation, in particular the regulation of venous capacitance.     

Distribution of PACAP (pituitary adenylate cyclase-activating polypeptide)-like and helospectin-like peptides in the teleost gut

Pituitary adenylate cyclase-activating polypeptide (PACAP) and helospectin are two vasoactive intestinal polypeptide (VIP)-related neuropeptides that have recently been demonstrated in the mammalian gut; the aim of this study was to reveal their occurrence and localisation in the gastrointestinal tract, swimbladder, urinary bladder and the vagal innervation of the gut of teleosts, using immunohistochemical methods on whole-mounts and sections of these tissues from the Atlantic cod, Gadus morhua and the rainbow trout, Oncorhynchus mykiss. Both PACAP-like and helospectin-like peptides were present in the gut wall of the two species. Immunoreactive nerve fibres were found in all layers but were most frequent in the myenteric plexus and along the circular muscle fibres. Immunoreactivity was also demonstrated in nerves innervating the swimbladder wall, the urinary bladder and blood vessels to the gut. Immunoreactive nerve cell bodies were found in the myenteric plexus of the gut and in the muscularis mucosae of the swimbladder. In the vagus nerve, non-immunoreactive nerve cells were surrounded by PACAP-immunoreactive fibres. Double staining revealed the coexistence of PACAP-like and helospectin-like peptides with VIP in all visualized nerve fibres and in some endocrine cells. It is concluded that PACAP-like and helospectin-like peptides coexist with VIP in nerves innervating the gut of two teleost species. The distribution suggests that both PACAP and helospectin, like VIP, are involved in the control of gut motility and secretion.     

Transient catecholaminergic (TC) cells in the vagus nerves and bowel of fetal mice: relationship to the development of enteric neurons

Catecholaminergic cells are transiently present during development of the fetal murine bowel. These transient catecholaminergic (TC) cells appear at Day E10, but by Day E13 can no longer be detected. In order to evaluate the hypothesis that these cells are the precursors of enteric neurons, we investigated the possibilities that TC cells coexpress neuronal and catecholaminergic markers, that they can be found along the presumed path followed by crest-derived cells migrating to the gut, and that they are proliferating. TC cells were identified immunocytochemically using polyclonal or monoclonal antibodies to tyrosine hydroxylase (TH). At Day E9.5, TH-immunoreactive cells were observed to be present along the wall of the primordial esophagus in lines that extended from the developing nodose ganglia down to the boundary of the stomach. At Day E9.5, TC cells were absent from the remaining foregut. These lines of esophageal TH-immunoreactive cells became continuous with similar cells in the wall of the stomach and duodenum on Day E10. Coincident expression of neurofilament immunoreactivity was seen in all of the esophageal TH-immunoreactive cells present at Day E9.5, as well as in the entire set of esophageal and lower enteric TH-immunoreactive cells present at Day E10 (or later); moreover, at Days E9.5 and E10, all of the neurofilament-immunoreactive cells in the esophagus, stomach, or duodenum were also TH-immunoreactive. In contrast, neurofilament immunoreactivity was not expressed by the endodermally derived pancreatic duct and islet cells, which were also TH-immunoreactive; nor could expression of neurofilament immunoreactivity be detected in the TH-immunoreactive cells of the nodose ganglia. It was not until Day E11 that neurofilament-immunoreactive cells, which did not coexpress TH immunoreactivity (the definitive phenotype of enteric neurons) began to appear in the gut. Vagal axons reached as far distally as the nodose ganglion on Day E9.5, the esophagogastric junction on Day E10, and did not enter the stomach until Day E11. When the vagus nerves reached their level, the TH-immunoreactive cells in the wall of the esophagus came to lie among the nerve fibers. TH-immunoreactive cells are thus present on the pathway ultimately followed by the vagus nerves, but they develop before vagal fibers reach their level. The vagal TH-immunoreactive cells, therefore, are probably not initially migrating on vagal fibers, but appear instead to be overtaken by the descending vagus nerves.(ABSTRACT TRUNCATED AT 400 WORDS)     

Immunochemical study of galanin in the cat digestive tract and autonomic ganglia

The presence of galanin was examined in the cat gut and related autonomic nervous structures using radioimmunoassay (RIA) and high performance liquid chromatography (HPLC). In the gut wall, the concentration of galanin-like immunoreactivity (GAL-LI) was assayed separately in the muscular layers with the nervous plexuses and in the mucosa and ranged from 0.35 to 0.55 pmol/g wet tissue. In the autonomic nervous structures, GAL-LI concentrations ranged from 0.22 (thoracic spinal ganglia) to 0.81 (inferior mesenteric ganglion) pmol/g wet tissue. The presence of galanin was checked by HPLC in the antrum, intestine, and colon. HPLC of extractable material revealed a major peak coeluting with the synthetic porcine peptide and minor earlier peaks representing likely different molecular forms of galanin. Our study strengthens the notion that galanin acts in nervous control of the cat gut functions.     

Effects of digestive status on the reptilian gut

Reptiles, including the Burmese python, Python molurus bivittatus, that feed at infrequent intervals show a prominent increase in gastrointestinal mass, metabolism and brush border transport rates after feeding. Current knowledge and theories around these phenomena, as well as studies on the innervation of the reptilian gut, are summarised in this review. Little is known about the putative changes in the nervous and humoral control systems of the gut, and it is not known whether feeding affects innervation and motility of the stomach and intestine. Using immunohistochemistry, we have investigated possible up/down regulation of several neurotransmitters in specimens that had been fasted for a minimum of 3 weeks and specimens that had ingested a large meal 2 days before the experiments were conducted. There were no major changes in the innervation by nerves containing calcitonin gene-related peptide (CGRP), galanin, nitric oxide synthase (NOS), pituitary adenylate cyclase-activating polypeptide (PACAP), somatostatin (SOM), substance P/neurokinin A (SP/NKA), or vasoactive intestinal polypeptide (VIP)-like immunoreactivity. Nor did we find any differences in the effect of substance P (stomach and intestine), galanin (intestine), or bradykinin (intestine) on motility in strip preparations from the gut wall. A significant increase in dry weight of the intestine was obtained 48 h after feeding. We conclude that although there are considerable changes in gut thickness and absorptive properties after feeding, the smooth muscle and its control appear little affected.     

Immunocytochemical localization of a galanin-like peptidergic system in the brain of two urodele and two anuran species (Amphibia).

Galanin-like immunoreactivity was localized in the brain of Urodela (Ambystoma, Pleurodeles) and Anura (Bufo, Xenopus) by immunocytochemistry with anti-porcine galanin antiserum. In the four species, immunoreactive perikarya were observed in the telencephalon (striatum, amygdala), diencephalon preoptic area mainly along the anterodorsal wall of the preoptic recessus, suprachiasmatic nucleus, lateral hypothalamus, ventral and dorsal infundibular nuclei, paraventricular organ, and rhombencephalon (nucleus of the solitary tract). Galaninergic fibres extended in similar regions and in the medial septum, ventral telencephalon, ventral hypothalamus, median eminence, and various mesencephalic and rhombencephalic regions. Contacts with the cerebrospinal fluid cavity occurred along the preoptic recessus (Ambystoma) and the ventral infundibular wall (all species). Fibres were scarce in the neurohypophysis. The distal and intermediate lobes of the pituitary were virtually devoid of immunoreactivity. The galaninergic system appeared more developed in adult amphibia than in young animals, suggesting the stimulating influence of sex steroids on the expression of galanin as previously described in Anguilla. The extensive distribution of the galanin-like immunoreactive neurons in amphibian brains suggests that this peptide may act as a neuromodulatur and/or neurotransmitter.     

The presence of a galanin-like peptide in the gut neuroendocrine system of Lampetra fluviatilis and Acipenser transmontanus: an immunohistochemical study

Galanin is a brain-gut neuropeptide present in the central and peripheral nervous systems of vertebrates. In the present survey, the galaninergic and the diffuse endocrine systems of the alimentary canal of the river lamprey, Lampetra fluviatilis, and the white sturgeon, Acipenser transmontanus, were studied by immunohistochemistry. The results show the presence of galanin-like immunoreactive endocrine cells in the gut of L. fluviatilis. In addition, a galanin-like immunoreactivity was detected in enteric intramural neurons of both species. It is conceivable that the galaninergic system plays in both species a role in the regulation of the gut muscle contractility and in the modulation of mucosal secretive/absorptive processes. In A. transmontanus, the presence of galanin-like immunoreactive nerve fibres associated with components of the gut associated-lymphoid tissue is possibly correlated with a control of the defensive events at this site. The presence of a galanin-like immunoreactivity in the neuroendocrine system of these two ancient fishes confirms the hypothesis on the early occurrence of this regulative molecule in the gastro-enteric system of vertebrates.     

Galanin-immunoreactive nerves in the rat iris: alterations induced by denervations

Summary The iris and choroid membrane of the adult rat contain nerve fibers expressing immunoreactivity to the neuropeptide galanin. The density and distribution of galanin-positive nerve fibers varied from iris to iris and, particularly, among animals. Smooth, non-terminal axons were seen running in nerve bundles consisting of otherwise negative fibers. From the choroid membrane these bundles reached the iris via the ciliary body. Axons were frequently seen to branch giving rise to a sparse system of varicose, single fibers in the dilator plate and sphincter area. Galanin-positive fibers were sometimes also seen outlining blood vessels.Capsaicin, in a dose that causes permanent depletion of substance P- and cholecystokinin-immunoreactive fibers in the iris, caused no change in amount of galanin-positive fibers. Removal of the superior cervical ganglion caused a rapid and pronounced increase in the number of galanin-immunoreactive nerve fibers. Similarly, removal of the ciliary ganglion appeared to increase galanin immunoreactivity, while removal of the pterygopalatine ganglion was less effective. Lesioning of the trigeminal ganglion caused a disappearance of galanin immunoreactivity. The sympathetectomy-induced increase was counteracted by capsaicin.Galanin-positive nerve cell bodies were present in both the superior cervical and the trigeminal ganglia. In the superior cervical ganglion, immunoreactive galanin did not seem to coexist with neuropeptide Y-positive cells; in the trigeminal ganglion, some galanin-positive cells also contained calcitonin gene-related peptide (CGRP) immunoreactivity, while most cells did not. In the iris, double-staining suggested that CGRP and galanin immunoreactivities were contained in different fiber populations.We conclude that the rat iris and choroid membrane contain a sparse plexus of nerve fibers expressing galanin-like immunoreactivity. It is suggested that these fibers are derived from the trigeminal ganglion. The iris is able to respond with a pronounced increase in number of galanin-immunoreactive nerve fibers to certain denervation procedures.     

Bombesin-like immunoreactive material in the gut, and the effect of bombesin on the stomach circulatory system of an elasmobranch fish, Squalus acanthias

The distribution, nature and amount of bombesin-like immunoreactivity (IR) in the gastrointestinal canal and its afferent vessels was investigated in the spiny dogfish (Squalus acanthias) together with the in vitro effect of synthetic bombesin on perfusion flow through the vascularly perfused dogfish stomach. Nerve fibres showing bombesin-like IR frequently occurred in the walls of the anterior mesenteric and coeliac arteries and the intrinsic vessels of the gut. Chromatographic studies revealed that multiple peaks of bombesin-like IR material were present in extracts of the spiny dogfish gastrointestinal vessels. Bombesin-like IR was also present in muscle and mucosal layers of the gut with higher levels in muscle compared with mucosa, and higher levels in the stomach than in the intestine and the rectum. Exogenous bombesin increased the flow through the vasculary perfused spiny dogfish stomach in a dose-dependent manner. Studies with tetrodotoxin and atropine showed that bombesin probably exerts its effect directly on the vascular musculature. It is concluded from this study that bombesin-like material is present in nerves innervating the gut circulatory system of the spiny dogfish. Bombesin may affect the blood-flow to the gastrointestinal canal, possibly via a direct effect on vascular smooth muscle.     

The development of the peripheral autonomic nervous system in relation to the gastro-intestinal tract

In this study the development of vagus nerves and the development of sympathetic nerves related to the development of the upper gastro-intestinal tract was studied in the rat from 12.5 days p.c. until birth by means of enzyme histochemical methods applied to sections and toto preparations. A striking time relation between the ingrowth of the vagus nerves as well as the sympathetic nerves and the appearance of acetylcholinesterase (AChE)-positive cells in the wall of the upper gastro-intestinal tract is established. The maturation of the upper enteric ganglion cells is dependent on the presence of a vagal influence. The vagal ingrowth of the stomach starts at about day 12.5 p.c. In AChE toto preparations it is established that the basic distribution pattern as described in the adult rat is complete at day 15 p.c. However, in contrast with the adult state, gastric branches can be traced up to the pylorus and the greater curvature until day 18 p.c. During the 18th day p.c. there is a tremendous increase in the surface area of the stomach. This increase in surface area of the gastric wall and relative decrease in vagal outgrowth leads to the adult configuration of vagal ramifications in relation to the wall of the stomach which can already be observed on the 19th day p.c.     

Immunohistochemical mapping of galanin-like immunoreactivity in the brain of the dogfish Scyliorhinus canicula.

The distribution of galanin-like immunoreactivity in the brain of the dogfish Scyliorhinus canicula was investigated using the indirect immunofluorescence technique. In the telencephalon, positive cells and fibers were located in the mid-caudal part of the area superficialis basalis, the n. septi caudoventralis and in the n. interstitialis commissurae anterioris. Most of the galanin-containing neurons observed in the hypothalamus were located in the magnocellular preoptic nucleus. Positive perikarya were also found in the n. lobi lateralis hypothalami and in the n. lateralis tuberis. A dense network of positive nerve processes was noted in the caudal part of the median eminence. In the dorso-caudal part of the diencephalon numerous immunoreactive neurons were seen in the recessus posterioris. A large bundle of galanin-containing fibers, which divided in two branches, was observed in the basal midbrain tegmentum. The widespread distribution of galanin-like material suggests that, in the dogfish, galanin may be involved in various brain functions including neuroendocrine regulations.     

Immunocytochemical localization of a galanin-like peptidergic system in the brain of two urodele and two anuran species (Amphibia)

Summary Galanin-like immunoreactivity was localized in the brain of Urodela (Ambystoma, Pleurodeles) and Anura (Bufo, Xenopus) by immunocytochemistry with anti-porcine galanin antiserum. In the four species, immunoreactive perikarya were observed in the telencephalon (striatum, amygdala), diencephalon preoptic area mainly along the anterodorsal wall of the preoptic recessus, suprachiasmatic nucleus, lateral hypothalamus, ventral and dorsal infundibular nuclei, paraventricular organ, and rhombencephalon (nucleus of the solitary tract). Galaninergic fibres extended in similar regions and in the medial septum, ventral telencephalon, ventral hypothalamus, median eminence, and various mesencephalic and rhombencephalic regions. Contacts with the cerebrospinal fluid cavity occurred along the preoptic recessus (Ambystoma) and the ventral infundibular wall (all species). Fibres were scarce in the neurohypophysis. The distal and intermediate lobes of the pituitary were virtually devoid of immunoreactivity. The galaninergic system appeared more developed in adult amphibia than in young animals, suggesting the stimulating influence of sex steroids on the expression of galanin as previously described inAnguilla. The extensive distribution of the galanin-like immunoreactive neurons in amphibian brains suggests that this peptide may act as a neuromodulatur and/or neurotransmitter.     

VIP-, substance P-, gastrin/CCK-, bombesin-, somatostatin- and glucagon-like immunoreactivities in the gut of the rainbow trout,Salmo gairdneri

Summary The presence of peptides in the gastrointestinal tract of the rainbow trout, Salmo gairdneri, was investigated immunocytochemically. VIP-like immunoreactivity was demonstrated in nerves in all layers of the stomach and the intestine, whereas substance P-like immunoreactivity was localized to endocrine cells, predominantly in the mucosa of the stomach, and to nerves mainly concentrated in the myenteric plexus throughout the gut. Endocrine cells reactive to gastrin/CCK antiserum were demonstrated in the intestinal mucosa, while no immunoreactivity was found in the stomach. Bombesin-immunoreactive and somatostatin-immunoreactive cells were localized in the stomach mucosa, and cells reactive to glucagon antiserum in the intestinal mucosa. Radioimmunoassay of stomach mucosa and muscle confirmed the presence of VIP-like and substance P-like immunoreactivity in these tissues, while gastrin/CCK-like immunoreactivity was low and bombesin-like immuno-reactivity was insignificant. In conclusion, molecules resembling the mammalian brain-gut peptides may be involved in the neuronal and hormonal control of gut function in fish.     

The distribution of GAWK-like immunoreactivity in neuroendocrine cells of the human gut,pancreas, adrenal and pituitary glands and its co-localisation with chromogranin B

Summary GAWK is a recently discovered peptide isolated from extracts of human pituitary gland and subsequently shown to be identical to sequence 420–493 of human chromogranin B. The distribution of this peptide was studied in human gut, pancreas, adrenal and pituitary glands using antisera to two portions of the 74 amino acid peptide (sequences 1–17 and 20–38). In addition, the co-existence of GAWK immunoreactivity with other peptides and chromogranin B was investigated using comparative immunocytochemistry.In the gut, GAWK was localised mainly to serotonin-containing cells of the mucosal epithelium, where electron microscopy showed it to be stored in typical electron-dense (250 nm diameter) granules, and to a moderate population of nerve fibres in the gut wall. Considerable quantities of GAWK-like immunoreactivity were measured in the gut, up to 36.3±18 pmol GAWK 1–17/g wet weight of tissue (mean±SEM) and 12.4±2.9 pmol GAWK 20–38/g. Chromatography of gut extracts revealed several GAWK-like immunoreactive peaks. GAWK-like immunoreactivity was also detected in endocrine cells of pancreas, pituitary gland and adrenal medulla, where the highest concentrations of GAWK-like immunoreactivity were measured (GAWK 1–17 2071.8±873.2 and GAWK 20–38 1292.7±542.7 pmol/g). Endocrine cells containing GAWK-like immunoreactivity were found also to be immunoreactive for chromogranin B.Our results define a discrete distribution of GAWK immunoreactivity in human endocrine cells and nerves and provide morphological support for the postulated precursor-product relationship between chromogranin B and GAWK. Details of the functions of this peptide are awaited.     

Distribution of CGRP-, somatostatin-, galanin-, VIP-, and substance P-immunoreactive nerve fibers in the chicken carotid body

Summary An immunoperoxidase method was used to investigate and compare the distribution of neuropeptide-immunoreactive (ir) nerve fibers and neurofilament-ir fibers in chick carotid body. The vagus nerve and its branches were intensely immunoreactive with an antiserum against chick neurofilaments. The branches from the vagus and the recurrent laryngeal nerves anastomosed within the connective tissue encircling the carotid body, and then entered the organ to form a network of neurofilament-ir fibers. Immunoreactivities for CGRP, somatostatin, galanin, VIP and substance P were found in the carotid body; they were located within varicose fibers. Immunoreactivity for each peptide was discretely and characteristically distributed. Dense networks of varicose CGRP-ir nerve fibers were found throughout the carotid body in close proximity to clusters of carotid body cells and to blood vessels. Substance P-ir fibers were distributed similarly to CGRP-ir fibers. Somatostatin-ir fibers appeared as patches distributed around chief cells. Numerous galanin- and VIP-ir nerve fibers were observed in the connective tissue surrounding the carotid body, but they occurred in only moderate densities in the parenchyma.     

The distribution of GAWK-like immunoreactivity in neuroendocrine cells of the human gut, pancreas, adrenal and pituitary glands and its co-localisation with chromogranin B

GAWK is a recently discovered peptide isolated from extracts of human pituitary gland and subsequently shown to be identical to sequence 420-493 of human chromogranin B. The distribution of this peptide was studied in human gut, pancreas, adrenal and pituitary glands using antisera to two portions of the 74 amino acid peptide (sequences 1-17 and 20-38). In addition, the co-existence of GAWK immunoreactivity with other peptides and chromogranin B was investigated using comparative immunocytochemistry. In the gut, GAWK was localised mainly to serotonin-containing cells of the mucosal epithelium, where electron microscopy showed it to be stored in typical electron-dense (250 nm diameter) granules, and to a moderate population of nerve fibres in the gut wall. Considerable quantities of GAWK-like immunoreactivity were measured in the gut, up to 36.3 +/- 18 pmol GAWK 1-17/g wet weight of tissue (mean +/- SEM) and 12.4 +/- 2.9 pmol GAWK 20-38/g. Chromatography of gut extracts revealed several GAWK-like immunoreactive peaks. GAWK-like immunoreactivity was also detected in endocrine cells of pancreas, pituitary gland and adrenal medulla, where the highest concentrations of GAWK-like immunoreactivity were measured (GAWK 1-17 2071.8 +/- 873.2 and GAWK 20-38 1292.7 +/- 542.7 pmol/g). Endocrine cells containing GAWK-like immunoreactivity were found also to be immunoreactive for chromogranin B. Our results define a discrete distribution of GAWK immunoreactivity in human endocrine cells and nerves and provide morphological support for the postulated precursor-product relationship between chromogranin B and GAWK. Details of the functions of this peptide are awaited.     

Distribution and ontogeny of VIP-like immunoreactivity in the gastro-entero-pancreatic system of a cartilaginous fish Scyliorhinus stellaris

Summary The presence, distribution and development of vasoactive intestinal polypeptide (VIP)-like immunoreactivity in the gastro-entero-pancreatic system of a cartilaginous fish Scyliorhinus stellaris (L.) was investigated by immunohistochemical methods utilizing mammalian VIP antisera. In the gut VIP-like immunoreactivity was observed in both nerves and endocrine cells. Endocrine cells with VIP-like material were only detected in the intestinal epithelium while nerve fibres containing VIP-like material were noted along the whole gastro-entero-pancreatic system, being more numerous in the pyloric sphincter and in the intestinal portion. Immunoreactive nerve cell bodies were encountered in the stomach and intestinal portions localized in the submucosa and in the myenteric plexus. Intestinal immunoreactive endocrine cells were already present in the first developmental stage considered (embryos aged 4 months). They grow in number and before birth reach a frequency higher than in adults. Nerves and cell bodies showing VIP-like immunoreactivity, appear later, before birth, as a few elements in the smooth muscular layer, but only after birth their distribution and frequency are similar to those found in adults. The faint immunofluorescence shown by the immunoreactive endocrine cells and their developmental pattern, which is always different from that observed in nervous elements, suggest the presence of at least two VIP-like substances in the gastro-entero-pancreatic system of S. stellaris.     

Immunohistochemical localization of bioactive peptides and amines associated with the chromaffin tissue of five species of fish

Biogenic peptides and amines associated with the chromaffin tissue in Atlantic cod (Gadus morhua), rainbow trout (Oncorhynchus mykiss), European eel (Anguilla anguilla), spiny dogfish (Squalus acanthias) and Atlantic hagfish (Myxine glutinosa) were identified utilizing immunohistochemical techniques. Within the posterior cardinal vein (PCV) in cod, trout and eel, a subpopulation of chromaffin cells displayed immunoreactivity to tyrosine hydroxylase (TH) and dopamine--hydroxylase (DH) but not to phenylethanolamine-N-methyltransferase (PNMT). TH-like immunorectivity was observed within cells in hagfish hearts. Nerve fibres displaying vasoactive intestinal peptide (VIP) immunoreactivity and pituitary adenylyl cyclase activating peptide (PACAP) immunoreactivity innervated cod, trout and ell chromaffin cells. In eel, neuropeptide Y (NPY)-like and peptide YY (PYY)-like immunoreactivity was located within cells in the PCV, including chromaffin cells. Serotonin-like immunoreactivity was observed within eel and cod chromaffin cells and in hagfish hearts. In the dogfish axillary bodies, nerves displaying TH-like, VIP-like, PACAP-like, substance P-like and galanin-like immunoreactivity were observed. These results are compared with those of other vertebrates, and potential roles for these substances in the control of catecholamine release are suggested.     

P2X2 purine receptor immunoreactivity of intraganglionic laminar endings in the mouse gastrointestinal tract

The distribution of P2X(2) purine receptor subunit immunoreactivity has been investigated in the mouse gastrointestinal tract. Immunoreactivity occurred in intraganglionic laminar endings (IGLEs) associated with myenteric ganglia throughout the gastrointestinal tract. In the esophagus, IGLEs supplied every myenteric ganglion. The proportion of ganglia supplied decreased from 85% in the stomach to 10% in the ileum, and from 50% in the caecum to 15% in the distal colon. There was substantial loss of IGLEs from myenteric ganglia of all abdominal regions after bilateral subdiaphragmatic section of the vagus nerves. IGLEs in the esophagus consisted of dense clusters of punctate immunoreactive varicosities. In the stomach and duodenum they had prominent lamellar processes and irregular, but smaller, lamellae were found in other regions. Rare immunoreactive IGLEs occurred in the submucosa of the distal colon. P2X(2) receptor immunoreactivity was on the surfaces and in the cytoplasm of a minority of nerve cells in myenteric ganglia. It is concluded that P2X(2) purine receptor immunoreactivity is a feature of IGLEs in the mouse, and that P2X receptor agonists may modulate sensitivity of the IGLEs.     

Immunohistochemical studies on peptide- and amine-containing endocrine cells and nerves in the gut and the rectal gland of the ratfish Chimaera monstrosa

Summary The occurrence and distribution of endocrine cells and nerves were immunohistochemically demonstrated in the gut and rectal gland of the ratfish Chimaera monstrosa (Holocephala). The epithelium of the gut mucosa revealed open-type endocrine cells exhibiting immunoreactivity for serotonin (5HT), gastrin/cholecystokinin (CCK), pancreatic polypeptide (PP)/FMRFamide, somatostatin, glucagon, substance P or gastrin-releasing peptide (GRP). The rectum contained a large number of closed-type endocrine cells in the basal layer of its stratified epithelium; the majority contained 5HT- and GRP-like immunoreactivity in the same cytoplasm, whereas others were immunoreactive for substance P. The rectal gland revealed closed-type endocrine cells located in the collecting duct epithelium. Most of these contained substance P-like immunoreactivity, although some reacted either to antibody against somatostatin or against 5HT. Four types of nerves were identified in the gut and the rectal gland. The nerve cells and fibers that were immunoreactive for vasoactive intestinal peptide (VIP) and GRP formed dense plexuses in the lamina propria, submucosa and muscular layer of the gut and rectal gland. A sparse network of gastrin- and 5HT-immunoreactive nerve fibers was found in the mucosa and the muscular layer of the gut. The present study demonstrated for the first time the occurrence of the closed-type endocrine cells in the mucosa of the rectum and rectal gland of the ratfish. These abundant cells presumably secrete 5HT and/or peptides in response to mechanical stimuli in the gut and the rectal gland. The peptide-containing nerves may be involved in the regulation of secretion by the rectal gland.