Occurrence and distribution of substance P- and CGRP-containing nerve fibers in gastric mucosa: species differences.
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Animals↗
Biomedical subjects
E Ekblad
Publications and source records attributed to E Ekblad.
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.
Adrenergic Fibers↗
Neuropeptide Y (NPY) co-exists with tyrosine hydroxylase and potentiates the adrenergic contractile response of vascular smooth muscle in the human uterine artery.
The human uterine artery was studied by immunocytochemistry and in vitro pharmacology. Nerve fibres containing immunoreactivity for neuropeptide Y (NPY) were encountered in the media, adventitia, smooth muscle layers and surrounding the vasa vasorum. Approximately 50% of the nerve fibres containing NPY also stored immunoreactivity for tyrosine hydroxylase (TH) and TH activity was found in no other fibres. Noradrenaline (NA) contracted the isolated uterine artery in a concentration dependent manner. The presence of increasing doses of NPY shifted the concentration-response curve for NA to the left. Consequently the pD2-values were increased indicating a potentiation of the adrenergic effects induced by NPY. The results demonstrate the existence of NPY in adrenergic nerve fibres surrounding the human uterine artery. A close co-operation between NPY and NA in the neuronal control of smooth muscle is suggested.
Adult↗
The neuroendocrine system of the gut--an update.
During the last few years the endocrine stomach has come into focus much due to the side-effects produced by powerful acid blockers. A sustained and marked inhibition of acid secretion in the rat results in hypergastrinemia, with gastrin cell hyperplasia, and a consequent hyperplasia of the ECL cells. This response of the ECL cells was predictable in view of previous observations that sustained hypergastrinemia causes ECL cell hyperplasia. While the gastrin cell hyperplasia levels off at about twice the normal cell density a few weeks after start of treatment, the ECL cells continue to proliferate for months to reach a five-fold higher density than normally. Evidence is accumulating that ECL cells proliferate through self replication. After life-long inhibition of acid production (high doses of ranitidine or omeprazole) or after extirpation of 75% of the acid-producing part of the stomach, ECL cell carcinoids develop. Endocrine cells in the gut often contain more than one putative messenger. Thus, gastrin cells in many species store GABA and peptide YY; in e.g. cat and man they store in addition a xenopsin-like peptide. Neuromedin U and pituitary adenylate cyclase activating peptide (PACAP) have recently been demonstrated in gut nerves. Their role in gut physiology remains to be identified.
Animals↗
Gastrin-releasing peptide: neuronal distribution and spatial relation to endocrine cells in the human upper gut.
By using immunocytochemical techniques, we have studied the distribution of gastrin releasing peptide (GRP)-containing neurons as well as the spatial relationship between these neurons and the endocrine cells in the human stomach and duodenum. Moderate numbers of immunoreactive fibers were distributed in the smooth muscle and submucosa of the stomach; they were more rare in the duodenal wall. Numerous GRP-containing nerve fibers were found in the oxyntic mucosa, the antral mucosa harboured only few GRP immunoreactive nerve fibers. The mucosa of the proximal duodenum was found to be virtually devoid of such fibers. Only occasionally did we observe signs of a direct contact between GRP-containing nerve fibers and gastrin and somatostatin cells in the antral mucosa. In the oxyntic mucosa GRP-containing nerve fibers sometimes seemed to contact endocrine cells, including somatostatin cells as well as individual parietal cells. In conclusion, although GRP-containing nerve fibers were quite numerous in the wall of the human upper gastro-intestinal (GI)-tract, we observed a lack of intimate spatial relationship between these fibers and endocrine cells in the antral mucosa, suggesting additive mechanisms to a direct innervation of gastrin cells and somatostatin cells by GRP nerve fibers explaining the physiological effects on hormonal release.
Adult↗
Muscarinic supersensitivity in the rat urinary bladder after capsaicin pretreatment.
The effects of capsaicin on urinary bladder function have been investigated in adult rats. Ten days after capsaicin treatment immunocytochemical investigations showed a nearly complete disappearance of substance P (SP) and calcitonin gene-related peptide (CGRP) in all parts of the bladder. Recordings of micturition patterns and cytometrical investigations in conscious animals revealed no functional effects of capsaicin treatment. In-vitro experiments showed that the contractile response to substance P was similar before and after capsaicin treatment and CGRP exerted no contractile effects on the urinary bladder in either group of rats. The concentration-response curve to carbachol as well as the frequency-response curve to electrical stimulation were significantly shifted to the left in bladder muscle after capsaicin treatment. However, the maximal responses were similar in control and capsaicin-treated bladders. In the presence of scopolamine the maximal response to electrical stimulation was clearly lower in bladders subjected to capsaicin treatment than in controls. In conclusion, depletion of substance P and CGRP in the rat urinary bladder by capsaicin induced no supersensitivity to these peptides. However, the increased sensitivity to carbachol and to electrical stimulation seen after capsaicin treatment indicates the development of a supersensitivity to muscarinic receptor stimulation. Despite this supersensitivity in vitro no functional effects of capsaicin treatment were found in vivo.
Animals↗
Serotonin uptake into cerebrovascular nerve fibers of rat, visualization by immunohistochemistry, disappearance following sympathectomy, and release during electrical stimulation.
Immunohistochemistry as well as in vitro uptake and release of [3H]5-HT were performed on pial arteries of rat to investigate the nature of 5-HT containing nerve fibers. Immunoreactive fibers were constantly found only in the basilar, vertebral and superior cerebellar arteries, while in the other parts of the circle of Willis, 5-HT immunofluorescent fibers were absent. After systemic treatment with tryptophan following inhibition of monoamine oxidase with nialamide the immunofluorescence intensity was markedly enhanced. The 5-HT immunoreactive fibers disappeared after superior cervical ganglionectomy or intraventricular administration of 6-hydroxydopamine, but persisted after administration of 5,6-dihydroxytryptamine. When isolated vessels were incubated in low concentration of 5-HT (1 nM) together with nialamide, a very dense plexus of 5-HT immunoreactive fibers appeared in all branches of the circle of Willis. Uptake and release experiments were carried out by incubation of arterial preparations with 3 nM [3H]5-HT (together with nialamide), followed by electrical field stimulation, or by exposure to tyramine or 124 mM potassium, all of which induced a 100%-350% increase in the tritium release over prestimulation values. Preincubation with cocaine and bilateral superior cervical ganglionectomy abolished or markedly attenuated the release upon all modes of stimulation. The results suggested that the 5-HT observed by immunohistochemistry in pial arteries is located in sympathetic nerve terminals where it may serve as a neuromodulator that is released during nerve activation.
Adrenergic Fibers↗
Co-existence of neuropeptides and differential inhibition of vasodilator responses by neuropeptide Y in guinea pig uterine arteries.
The co-localization of substance P (SP) with calcitonin gene-related peptide (CGRP), and vasoactive intestinal peptide (VIP) with neuropeptide Y (NPY) of the guinea pig uterine artery were investigated with immunocytochemistry. The SP/CGRP fibre population was distinct from the VIP/NPY fibre population. Both types of fibres ran in the medial-adventitial border, and appeared as coarsed and fine varicosed. Uterine arterial dilatation was evoked by acetylcholine (ACh), SP, CGRP, and VIP in precontracted arteries as examined by a sensitive in vitro method. Strong relaxations were seen by ACh, CGRP and VIP. NPY had no relaxant effect per se but was found to be a potent inhibitor of vasodilation induced by ACh and SP, while relaxations induced by VIP and CGRP were unaffected. The functional significance of NPY in the uterine artery may to a large extent be to increase tension not only by potentiation of contraction but additionally by inhibiting vasodilator responses.
Animals↗
Neuropeptides in the human appendix. Distribution and motor effects.
At present our knowledge of enteric peptide-containing neurons in man is limited. In this study we have used human appendices removed at surgery to examine the peptidergic innervation by immunocytochemistry, immunochemistry, and pharmacological in vitro experiments. Immunocytochemistry revealed a variety of peptide-containing nerve fiber populations in the human appendix. VIP/PHI-, VIP/PHI/NPY-, SP/NKA-, galanin-, and enkephalin-containing nerve fibers were numerous; CGRP- and GRP-containing nerve fibers were moderate in number, while only scattered NPY-, enkephalin/BAM-, and somatostatin-containing nerve fibers could be found. No CCK-, dynorphin A-, or dynorphin B-immunoreactive nerve fibers could be detected. The coexistence of VIP/PHI, SP/NKA, and enkaphalin/BAM can be anticipated from the known sequence of their respective precursors. However, the coexistence of VIP/PHI and NPY was unexpected but corroborates previous observations in other species. Interestingly, SP and CGRP did not seem to coexist in nerve fibers of the human appendix. Immunochemistry (RIA and HPLC) confirmed the presence of VIP, NPY, SP, galanin, CGRP, GRP, enkephalin, and somatostatin. Motor activity studies suggest that acetylcholine plays a major role in the electrically evoked contractions, since atropine suppressed these contractions. Galanin (10(-8)-10(-6) M) and GRP (10(-9)-10(-7) M) caused concentration-dependent contractions that were unaffected by tetrodotoxin and thus probably reflect a direct action on smooth muscle receptors. GRP (10(-9) M) enhanced the electrically induced cholinergic contraction (to 193 +/- 24%), while met-enkephalin (10(-6) M) reduced it (to 54 +/- 6%). Both peptides failed to affect the contractile response to exogenous acetylcholine and probably act to modulate the release of acetylcholine. NPY, VIP, CGRP, SP, and somatostatin failed to induce contraction or to affect the electrically evoked contractions.
Appendix↗
Involvement of perivascular neuropeptide Y nerve fibres in uterine arterial vasoconstriction in conjunction with pregnancy.
The perivascular neuropeptide Y (NPY) innervation and its relation to adrenergic nerves of uterine arteries from non-pregnant and pregnant guinea pigs was analyzed immunocytochemically. The NPY content of the uterine artery was, in addition, measured radioimmunologically (RIA). Vasomotor effects of NPY per se and in combination with other vasoconstrictors were examined using a sensitive in vitro method. Pregnancy did not visibly affect density and distribution of NPY-immunoreactive fibres. The NPY fibres contained in addition immunoreactivity to dopamine-beta-hydroxylase (marker for noradrenergic neurons). RIA revealed a slight decrease of NPY content during pregnancy, probably due to the increased smooth muscle volume of uterine arteries. The contractile effect of NPY on uterine arteries was weak, while vasoconstriction induced by various agonists was potentiated by NPY, particularly during pregnancy. It is concluded that perivascular NPY-containing nerve fibres may be involved in the dramatic blood flow alterations that occur in the uterine circulation in connection with pregnancy and partus.
Animals↗
Projections of enteric peptide-containing neurons in the rat.
In order to understand better the neuronal circuitry involved in the regulation of gut functions, we have studied the distribution and projections of those enteric neurons in the rat intestines that contain vasoactive intestinal peptide (VIP), neuropeptide Y (NPY), galanin, substance P (SP), calcitonin gene-related peptide (CGRP), gastrin releasing peptide (GRP), somatostatin and enkephalin. The origin of the peptide-containing nerve fibers was examined by immunocytochemistry after extrinsic denervation. Most of them were found to be intramural in origin, each population displaying its own characteristic topographic distribution. The projections of each neuronal population were studied immunocytochemically by examining the subsequent axonal degeneration after local severing of nervous pathways. This study revealed that myenteric neurons issue predominantly descending projections to other myenteric ganglia and to the muscle layers. Submucous neurons project to other submucous ganglia and to the mucosa and submucosa. Most of these neurons issue both ascending and descending projections. The projection distances varied considerably between the different neuronal populations, the majority being in the range of 4-10 mm. Myenteric GRP and galanin neurons in the small intestine issued the longest projections, 20 and 15 mm, respectively. The shortest projections were those issued from myenteric VIP/NPY neurons and submucosal galanin and GRP neurons in the small intestine and from submucosal VIP neurons in the large intestine (2 mm in length). On the whole our results on the projections of enteric neurons in the rat agree with observations in the guinea pig and dog. However, there are species differences that remain to be explained.
Animals↗
The neuroendocrine system of the gut.
The digestive tract is the richest source of regulatory peptides outside the brain. Such peptides occur all along the gut in the neuroendocrine system which is composed of endocrine/paracrine cells disseminated in the epithelium and of intrinsic neurons that form continuous ganglionic chains in the submucosa and in the muscle layer. Some endocrine/paracrine cells, particularly in the stomach, still have not been associated with an identified regulatory peptide implying that our present knowledge is far from complete. The intracellular processing of regulatory peptide precursors involves multi-step proteolytic cleavage generating several fragments. In many instances more than one biologically active peptide is generated from one and the same precursor. In addition, certain endocrine/paracrine cells and neurons have been found to produce more than one peptide precursor and some are known to harbour 'classical' neurotransmitters, such as 5-hydroxytryptamine, histamine and GABA as well as regulatory peptides. Key questions for the future are the functional significance of the coexistence of multiple messengers within the same cells and the details of how the endocrine/paracrine cells and the neurons in the gut interact.
Animals↗
Immunocytochemical localization of galanin in the rat male and female genital tracts and motor effects in vitro.
Galanin, a recently discovered neuropeptide, was studied in the rat male and female reproductive tracts by immunocytochemistry and in vitro pharmacology. Nerve fibers containing galanin immunoreactivity were most abundant in the female paracervical tissue, where they surrounded non-immunoreactive ganglion cells. Galanin nerves were also found in the uterus and Fallopian tubes, as well as in the vas deferens. When tested in vitro galanin contracted the smooth muscle of both the uterine horn and cervix. Galanin also slightly potentiated the response to electrical field stimulation in preparations from the uterine cervix and vas deferens, but it had no effect on the seminal vesicle. Galanin-(1-10), an N-terminal residue of galanin, also contracted the uterine horn, though higher concentrations were required. The neurally induced contractions were not influenced by galanin-(1-10) in any of the smooth muscle preparations tested. The muscle receptors mediating the direct contractile effects in the uterine horn seem to require the N-terminus of galanin, while the neuromodulatory effects on the electrically induced contractile activity seem to need the C-terminal part or the whole galanin molecule. Galanin may thus function as a neuromediator in the rat male and female genital organs.
Animals↗
Projections of peptide-containing neurons in rat colon.
The distribution, origin and projections of nerve fibers containing vasoactive intestinal peptide, substance P, neuropeptide Y, galanin, gastrin-releasing peptide, calcitonin gene-related peptide, somatostatin or enkephalin were studied in the midcolon of the rat by immunocytochemistry and immunochemistry. Most of these nerve fibers had an intramural origin as was established by extrinsic denervation (serving of mesenterial nerves). Extrinsic denervation eliminated neuropeptide Y-containing fibers of presumably sympathetic origin together with sensory nerve fibers containing both substance P and calcitonin gene-related peptide. Co-existence of two peptides in the same neuron was studied by double immunostaining. This revealed co-existence of neuropeptide Y and vasoactive intestinal peptide in one population of intramural neurons; an additional population of intramural neurons was found to contain vasoactive intestinal peptide but not neuropeptide Y. All somatostatin-containing neurons in the submucous ganglia were found to harbor calcitonin gene-related peptide. A much larger population of submucous neurons containing calcitonin gene-related but not somatostatin was also detected. Some perivascular calcitonin gene-related peptide-containing nerve fibers (of intrinsic origin) harbored vasoactive intestinal peptide while others (of extrinsic origin) harbored substance P. The polarities and projections of the various peptide-containing intramural neurons in the transverse colon were studied by analysing the loss of nerve fibers upon local disruption of enteric nervous pathways (myectomy or intestinal clamping). Myenteric neurons containing vasoactive intestinal peptide, galanin, gastrin-releasing peptide, calcitonin gene-related peptide, somatostatin or vasoactive intestinal peptide/neuropeptide Y gave off 5-10-mm-long descending projections while those containing substance P or enkephalin issued approx. 5-mm-long ascending projections. Submucous neurons containing calcitonin gene-related peptide, somatostatin/calcitonin gene-related peptide or gastrin-releasing peptide issued both ascending (2-6 mm) and descending (2-6 mm) projections, those containing vasoactive intestinal peptide issued ascending (approx. 2 mm) projections, while those containing galanin or vasoactive intestinal peptide/neuropeptide Y lacked demonstrable oro-anal projections. Enkephalin-containing fibers could not be detected in the mucosa and the mucosal substance P-containing nerve fibers were too few to enable us to delineate their projections.
Animals↗
Return of nerve fibers containing gastrin-releasing peptide in rat small intestine after local removal of myenteric ganglia.
Gastrin-releasing peptide is a neuropeptide with a wide distribution in the rat small intestine. Most of the GRP-containing fibers are intramural in origin. Local severing of myenteric GRP neurons by circumferential removal of the outer longitudinal muscle layer together with the adherent myenteric ganglia (myectomy) in a segment of the rat jejunum resulted in the disappearance of GRP fibers from the myectomized circular muscle and from myenteric ganglia and both muscle layers for approximately 10 mm anally to the lesion. As examined at different time intervals up to 60 weeks postoperatively fine-varicose GRP fibers of a normal appearance were found to return gradually to the portion anal to the lesion beginning at 20 weeks, first in the more distal portions and then (after 40-60 weeks) also in the more proximally located portions. Also the circular muscle in the myectomized segment became reinnervated during this time period. These fibers were notably coarse, more numerous than in control circular muscle, and arranged in thick bundles (hyperinnervation). Such nerve bundles were particularly frequent 40 weeks after the operation. The results indicate a remarkable plasticity of enteric neurons.
Animals↗
Vasoactive intestinal peptide in the peripheral nervous system.
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Animals↗
[The neuroendocrine system of the gastrointestinal tract].
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Digestive System↗
Projections of peptide-containing neurons in rat small intestine.
The distribution, origin and projections of nerve fibers containing vasoactive intestinal peptide, neuropeptide Y, somatostatin, substance P, enkephalin and calcitonin gene-related peptide were studied in the rat jejunum by immunocytochemistry and immunochemistry. Their origin was determined by the use of various procedures for extrinsic denervation (chemical sympathectomy, bilateral vagotomy or clamping of mesenterial nerves). The terminations of the different types of intramural nerve fibers were identified by examination of the loss of nerve fibers that followed local disruption of enteric nervous pathways (intestinal myectomy, transection or clamping). The majority of the peptide-containing nerve fibers in the gut wall were intramural in origin, each nerve fiber population having its own characteristic distribution and projection pattern. Nerve fibers emanating from the myenteric ganglia terminated within the myenteric ganglia and in the smooth muscle layers: those storing vasoactive intestinal peptide/neuropeptide Y, somatostatin and substance P were descending, those storing enkephalin were ascending and those containing calcitonin gene-related peptide projected in both directions. Nerve fibers emanating from the submucous ganglia terminated mainly within the submucous ganglia and in the mucosa: those storing calcitonin gene-related peptide or vasoactive intestinal peptide/neuropeptide Y were ascending and those storing substance P or somatostatin were both ascending and descending. Enkephalin nerve fibers could not be detected in the mucosa.
Animals↗