Intramural Blood Vessels Research Articles

Comparing the effects of transcranial alternating current and temporal interference (tTIS) electric stimulation through whole-brain mapping of c-Fos immunoreactivity.

The analysis of the topography of brain neuromodulation following transcranial alternating current (AC) stimulation is relevant for defining strategies directed to specific nuclei stimulation in patients. Among the different procedures of AC stimulation, temporal interference (tTIS) is a novel method for non-invasive neuromodulation of specific deep brain targets. However, little information is currently available about its tissue effects and its activation topography in in vivo animal models. After a single session (30 min, 0.12 mA) of transcranial alternate current (2,000 Hz; ES/AC group) or tTIS (2,000/2,010 Hz; Es/tTIS group) stimulation, rat brains were explored by whole-brain mapping analysis of c-Fos immunostained serial sections. For this analysis, we used two mapping methods, namely density-to-color processed channels (independent component analysis (ICA) and graphical representation (MATLAB) of morphometrical and densitometrical values obtained by density threshold segmentation. In addition, to assess tissue effects, alternate serial sections were stained for glial fibrillary acidic protein (GFAP), ionized calcium-binding adapter molecule 1 (Iba1), and Nissl. AC stimulation induced a mild superficial increase in c-Fos immunoreactivity. However, tTIS stimulation globally decreased the number of c-Fos-positive neurons and increased blood brain barrier cell immunoreactivity. tTIS also had a stronger effect around the electrode placement area and preserved neuronal activation better in restricted areas of the deep brain (directional stimulation). The enhanced activation of intramural blood vessels' cells and perivascular astrocytes suggests that low-frequency interference (10 Hz) may also have a trophic effect.

Optical Coherence Tomography Angiography and Attenuation Imaging for Label-Free Observation of Functional Changes in the Intestine after Sympathectomy: A Pilot Study

We present in this study optical coherence tomography angiography (OCTA) and OCT attenuation imaging (OCTAI) for in vivo non-destructive visualization of intramural blood and lymphatic vessels of the intestine wall. Rabbit small intestine in the norm and after thoracolumbar sympathectomy served as the object of the intraoperative study. Compared to OCTA real-time imaging, OCTAI takes several minutes and can be termed as “nearly real time”. OCTAI signal processing was modified to take into account the signal-to-noise ratio and the final thickness of the intestine wall. The results showed that, after sympathectomy, changes in functioning of intramural blood and lymphatic vessels were observed with a high statistical significance. The occurrence of trauma-induced constriction of the blood and lymphatic vessels led to an especially pronounced decrease in the length of small-caliber (<30 µm) blood vessels (p < 10−5), as well as in the volumetric density of lymphatic vessels (on average by ~50%) compared to their initial state. Remarkably, OCTA/OCTAI modalities provide the unique ability for “nearly-instant detection” of changes in functional status of the tissues, long before they become visible on histology. The proposed approach can be used in further experiments to clarify the mechanisms of changes in intestinal blood and lymph flows in response to trauma of the nervous system. Furthermore, potentially it can be used intraoperatively in patients requiring express diagnosis of the state of intramural blood and lymph circulation.

Retroperitoneal lymphatic malformation in a dog

BackgroundLymphatic vascular malformations are rare findings in canine patients with six reports available in veterinary literature. Retroperitoneal cystic lymphatic malformations have not been described previously in canine patients and neither has the use of immunohistochemistry to determine their origin, i.e. vascular versus lymphatic.Case presentationAn 8-year-old neutered female Cocker spaniel was referred for pollakiuria, dysuria and a painful abdomen. Computed tomography scanning of the abdomen showed a fluid filled structure adjacent to the urinary bladder. During surgical exploration, a thin walled cystic structure with sero-haemorrhagic fluid was found, extending from the retroperitoneal space into the abdomen. The mass was excised and submitted for histopathology, revealing a cystic mass lined by a fibrovascular capsule within the retroperitoneal/mesenteric adipose tissue. The inner surface of the cyst was lined by a single layer of bland, flattened spindle cells. Intramural blood vessels were well differentiated, with perivascular haemorrhage. On recurrence 11 months later, the mass was excised for the second time and a PleuralPort (Norfolk Animal products) was placed. Fifteen months after initial presentation, progression occurred with haemorrhagic fluid in the cystic space, pleural- and abdominal cavities and the owners opted for euthanasia. Histopathology and positive immunohistochemistry for lymphatic markers lymphatic vessel endothelial hyaluronic acid receptor-1 (LYVE-1) and prospero homeobox protein-1 (PROX-1) confirmed a lymphatic vascular origin of the cystic structure.ConclusionsTo our experience, a definitive diagnosis of retroperitoneal cystic malformation of lymphatic origin could be done only by combining the clinical presentation, advanced imaging, histopathology and LYVE-1 and PROX-1 immunohistochemistry. This is the first report of a vascular malformation in a dog where immunohistochemistry was used to make a final diagnosis. A lymphatic malformation, even if rare, should be added on the list of the differential diagnosis in a patient with a retroperitoneal cystic structure containing serohaemorrhagic fluid. Results of this case report can aid in diagnosis of future cases, however, further studies on therapy and management are needed to provide additional information about optimal treatment of these patients.

Bidomain Predictions of Virtual Electrode-Induced Make and Break Excitations around Blood Vessels

Virtual electrodes formed by field stimulation during defibrillation of cardiac tissue play an important role in eliciting activations. It has been suggested that the coronary vasculature is an important source of virtual electrodes, especially during low-energy defibrillation. This work aims to further the understanding of how virtual electrodes from the coronary vasculature influence defibrillation outcomes. Using the bidomain model, we investigated how field stimulation elicited activations from virtual electrodes around idealized intramural blood vessels. Strength-interval curves, which quantify the stimulus strength required to elicit wavefront propagation from the vessels at different states of tissue refractoriness, were computed for each idealized geometry. Make excitations occurred at late diastolic intervals, originating from regions of depolarization around the vessel. Break excitations occurred at early diastolic intervals, whereby the vessels were able to excite surrounding refractory tissue due to the local restoration of excitability by virtual electrode-induced hyperpolarizations. Overall, strength-interval curves had similar morphologies and underlying excitation mechanisms compared with previous experimental and numerical unipolar stimulation studies of cardiac tissue. Including the presence of the vessel wall increased the field strength required for make excitations but decreased the field strength required for break excitations, and the field strength at which break excitations occurred was generally greater than 5 V/cm. Finally, in a more realistic ventricular slice geometry, the proximity of virtual electrodes around subepicardial vessels was seen to cause break excitations in the form of propagating unstable wavelets to the subepicardial layer. Representing the blood vessel wall microstructure in computational bidomain models of defibrillation is recommended as it significantly alters the electrophysiological response of the vessel to field stimulation. Although vessels may facilitate excitation of relatively refractory tissue via break excitations, the field strength required for this is generally greater than those used in the literature on low-energy defibrillation. However, the high-intensity shocks used in standard defibrillation may elicit break excitation propagation from the coronary vasculature.

Investigating the Role of the Coronary Vasculature in the Mechanisms of Defibrillation

The direct role of coronary vessels in defibrillation, although hypothesized to be important, remains to be elucidated. We investigated how vessel-induced virtual electrode polarizations assist reentry termination. A highly anatomically detailed rabbit ventricular slice bidomain computer model was constructed from 25-μm magnetic resonance data, faithfully representing both structural and electric properties of blood vessels. For comparison, an equivalent simplified model with intramural cavities filled in was also built. Following fibrillation induction, 6 initial states were selected, and biphasic shocks (5-70 V) were applied using a realistic implanted cardioverter-defibrillator electrode configuration. A fundamental mechanism of biphasic defibrillation was uncovered in both models, involving successive break excitations (after each shock phase) emanating from opposing myocardial surfaces (in septum and left ventricle), which rapidly closed down excitable gaps. The presence of vessels accelerated this process, achieving more-rapid and successful defibrillation. Defibrillation failed in 5 cases (all because of initiation of new activity) compared with 8 with the simplified model (5/8 failures because of surviving activity). At stronger shocks, virtual electrodes formed around vessels, rapidly activating intramural tissue because of break excitations, assisting the main defibrillation mechanism, and eliminating all activity <15 ms of shock end in 60% of successful shocks (36% in simplified model). Subsequent analysis identified that only vessels >200 μm in diameter participated through this mechanism. Consequently, wavefronts could survive intramurally in the simplified model, leading to reentry and shock failure. We provide new insight into defibrillation mechanisms by showing how intramural blood vessels facilitate more-effective elimination of existing wavefronts, rapid closing down of excitable gaps, and successful defibrillation and give guidance toward the required resolution of cardiac imaging and model generation endeavors for mechanistic defibrillation analysis.

Identification of Medium/High-Threshold Extrinsic Mechanosensitive Afferent Nerves to the Gastrointestinal Tract

Large distentions reliably evoke sensation from the noninflamed, nonischemic bowel, but the specialized afferent axonal structures responsible have not been morphologically identified. We investigated whether their transduction sites are located on major blood vessels close to and within the gut wall. In vitro extracellular recordings were made from mesenteric nerve trunks in guinea pig ileum, combined with rapid axonal dye filling and immunohistochemical analysis of nerve trunks. Recordings revealed sensory fibers with focal mechanosensitive sites in the mesenteries that could be activated by von Frey hairs and by stretch. Dye filling revealed varicose branching sensory axons on mesenteric blood vessels but no other anatomically specialized structures in mesenteric membranes or the serosa. Large-amplitude stretch and von Frey hairs also activated sensory endings within the gut wall itself but only if the submucosa was present; mechanotransduction sites in the serosa or outer muscle layers were sparse. Mechanosensitive sites in submucosa were exclusively associated with submucosal blood vessels. Submucosal endings had significantly higher thresholds to stretch than specialized low-threshold mechanoreceptors characterized previously in the rectum (P < .05) and were therefore classified as medium/high-threshold mechanoreceptors. Capsaicin (0.3-1 micromol/L) activated most mechanosensitive mesenteric (68%) and submucosal (85%) afferent endings. Similar intramural mechanosensitive afferent endings on blood vessels also exist in the colon and bladder. Varicose branching axons of sensory neurons on intramural blood vessels, previously shown to mediate sensory vasodilation, are transduction sites for medium/high-threshold, stretch-sensitive mechanoreceptors, encoding large distentions in hollow viscera.

Preoperative bowel ultrasound corresponds to intraoperative and histopathological findings in active Crohn's disease

Bowel ultrasound has recently been proved useful in the assessment of bowel disease. Active Crohns disease (CD) is associated with neovasculanzation, and bowel loops affected by CD are thickened and loss of bowel wall stratification are often seen in affected bowel segments. These findings are readily visible with high4requency transcutaneous ultrasound. However, uncertainty persists as to its diagnostic role. Aim: to compare preoperative ultrasound with intraoperative and histopathological findings in active CD. Methods: 15 patients with active CD admitted for surgery underwent bowel ultrasound (Siemens elegra, 7.5 MHz) the day before operation. The extent and localisation of disease, findings of stenosis, wall thickness and wall stiffness detected on US were compared with those seen intraoperatively. Stratification of wall layers and density of intramural blood vessels were evaluated by power Doppler ultrasound and compared with histopathology. Results: Ileocecal involvment was observed in 5 patients, small bowel in 8 pattents, only large bowel in 1 patients, and combined small and large bowel in 1 patient. 12 patients were resected, tn one patient only stricturoplasty and in 2 patients both resection and stricruroplasty were performed. Agreement was observed between ultrasound and surgery: localisation of affected loops: 100%, number of affected loops: 54% (underestimation by ultrasound), stenosis: 92%, wall stiffness/fibrosis: 100%. 3 fmtulae were seen on ultrasound and 2 were demonstrated intraoperatively. Loss of stratification of wall layers were seen on ultrasound in 2 patients, corresponding with transmural fibrosis seen on histology. High density of intramural vessels were seen on ultrasound in 10 patients and these findings were seen as neovascularization in the inflamed tissue between mucosa and submucosa and as dilatation of already existing vessels in the submucosa on histology. Inflammation in the myemeric plexus occurred in 13 patients. Conclusion: Agreement between ultrasound and surgery was found for localisation and stenosis Loss of bowel wall stratification on US was confirmed as fibrotic tissue on histology, and intramural vessels on ultrasound could be demonstrated histologically as both neovascularization in inflamed tissue and dilation of submucosal vessels.

German experience with endoscopic transmural drainage for pancreatic pseudocysts

Background: Endoscopic drainage provides a good alternative or supplement to a surgical approach for the therapy of pancreatic pseudocysts.Methods: Between 1987 and 2000, 47 patients had been treated for pancreatic pseudocysts by transmural or transductal drainage. In 79% the pseudocysts were due to chronic pancreatitis mainly caused by alcoholism. The main symptoms were abdominal pain in 85% of patients and loss of appetite or weight in 60% of patients. In 17% of patients, signs of septicemia were observed.Results: In 42 patients pancreatic pseudocysts disappeared completely. In the remaining five cases drainage was not successful. Six patients suffered a relapse 7–38 months after drainage. No other recurrences were followed up within 4–10 years. In another six patients the prostheses were renewed because of occlusion or dislocation. Overall six patients had to undergo surgery, three patients because of relapsing cyst, two patients because of insufficient drainage and one patient because of severe bleeding. There was no case of death related to the endoscopic treatment.Conclusions: Since the development of a modified needle type cystotom, the puncture and insertion of the prosthesis for pancreatic cyst drainage is less precarious and quicker. The endoscopic sonography is a valuable supplement to the diagnostic procedure to localize the optimal spot for puncture and to avoid hemorrhage because of damage of intramural or extramural blood vessels. Advantages of endoscopic drainage are minimal invasiveness, short period of hospitalization and low costs. These aspects make endoscopic therapy the first choice of treatment of pancreatic pseudocysts.

Structural changes in the rat bladder after acute outlet obstruction.

The urinary bladder of adult female rats was subjected to complete outlet obstruction for periods of up to 24 h. Within 2 h the obstruction led to a rise in intravesical pressure to about 80 mmH2O. Subsequently, the pressure remained high but declined slightly. After 24 h of complete obstruction the bladder was maximally distended, but its volume was similar to that of a control bladder fully distended, indicating that overstretch (or overdistension) occurs only to a very limited degree. After 6 h of obstruction there was congestion of all the intramural blood vessels and extravasation of red blood cells from some vessels of the mucosa. At 12 h and 24 h the extravasation was very substantial and there was also infiltration of erythrocytes in the muscle layer. Ultrastructurally, there were several damaged nerve endings (but no changes in the nerve trunks) and, occasionally, damaged muscle cells. Removal of the obstruction after 24 h was followed by resorption of the extravasate, partly by phagocytosis by muscle cells, a process which lasted 4-6 days, and by 7 days damaged varicosities and muscle cells became uncommon. We conclude that the changes observed in the bladder wall following complete obstruction are caused more by haemorrhage and ischaemia than by overstretch and that the changes are reversed when outlet conditions are normalized.

Laminin localization in enterocytic basement membrane of rat small bowel grafts. A light and electron microscopic study.

In vitro laminins stimulate numerous biological effects, such as cell migration, proliferation, attachment and differentiation. In vitro laminins influence immunocompetent cells and in vivo possibly play an important role in graft rejection. To establish how laminins could be involved in the regulation of acute rejection of small bowel allografts (with and without immunosuppression), we investigated laminin distribution in rat small bowel allografts four days after transplantation, i.e., before the onset of histological signs of rejection, using antibodies against alpha1, beta1, gamma1 chain of laminin-1. In immunosuppressed allografts, the ultrastructure of the enterocytic basement membrane appeared normal, but no laminin staining was seen in this membrane, although basement membranes of intramural blood vessels and muscle cells were normally stained. In non-operated immunosuppressed rats, laminin staining was clearly reduced in the enterocytic basement membrane, demonstrating that cyclosporin A is able to affect this membrane. Since only rats in which laminin is altered survive, this laminin alteration in the enterocytic basement membrane presumably plays an important role in overcoming the acute rejection.

Desmin myopathy involving cardiac, skeletal, and vascular smooth muscle: Report of a case with immunoelectron microscopy

Desmin myopathy is a rare idiopathic disorder characterized by abnormal aggregates of desmin-type intermediate filaments, which affects cardiac and skeletal muscle, and rarely the intestinal smooth muscle. We report a 42-year-old woman with atrial fibrillation and progressive restrictive cardiomyopathy. Left ventricular biopsy, cardiac explant, and subsequent autopsy study of skeletal muscle revealed cytoplasmic granulo-filamentous inclusions that were continuous with Z-lines and were immunoreactive for desmin filaments both at the light immunohistochemical and electron microscopic level. In addition, we report the presence of characteristic inclusions within the smooth muscle of intramural coronary blood vessels. This is the first description of desmin inclusions within vascular smooth muscle, and underscores the systemic nature of this rare myopathy.

Distribution of nitric oxide synthase in the esophagus of the cat and monkey

The distribution of nitrergic neurons and processes in the esophagus of the cat and monkey was studied by light microscopic immunocytochemistry using a specific antibody against purified rat brain nitric oxide synthase and immunoperoxidase procedures. Immunoreactive nerve fibers were found pervading the myenteric plexus, submucous plexus and plexus of the muscularis mucosae, and particularly in the lower esophagus a few immunoreactive fibers entered the epithelium as free nerve endings, some of which derived from perivascular fibers. In the upper esophagus immunoreactive motor end-plates were found in the striated muscle. Thirty–forty-five percent of neuronal cell bodies found in the intramural ganglia and along the course of nerve fiber bundles were immunoreactive and were of the three morphological types earlier described. In the intramural ganglia immunoreactive nerve fibers formed a plexus in which varicose nerve terminals were in close relation to immunoreactive and non-immunoreactive neurons. The intramural blood vessels that crossed the different layers of the esophageal wall were surrounded by paravascular and perivascular plexuses containing immunoreactive nerve fibers. The anatomical findings suggest that nitric oxide is involved in neural communication and in the control of peristalsis and vascular tone in the esophagus. In the lower esophagus a few nitrergic nerve fibers are anatomically disposed to subserve a sensory-motor function.

Clinical importance of intramural blood vessels in the sino-atrial segment of the conducting system of the heart.

We studied the morphology and histology of intramural vessels in the sino-atrial [S-A] segment of the cardiac conducting system because of the clinical relevance of the anatomy of the microvascular system for those performing cardiac surgery or coronary angiography, catheterization or arterialization. In 25 human and 25 canine hearts the vasculature was fixed by the Komahidze method, the anatomy was studied and sections were stained and studied by microscopy. Of clinical importance is a finding of considerable variation in the exact anatomy of the arterial supply. The sinonodal artery is a large artery originating from the right or left coronary arteries. In some cases the coronary arterial course could not be demonstrable by coronary angiography thus increasing the risk of coronary artery surgery at the site. Cross connections also permit the extra-cardiac circulation to supply the nodal tissue. The S-A node has a rich intramural network of anastomosing blood vessels which is of surgical importance in the case of damage and surgical procedures. The density of the capillary network in the node is greater than that in adjacent atrial tissue. The distribution and density of the smallest anastomotic blood vessels were different in various parts of the node, the capillary net was most dense in sections from dorsal parts of the S-A node. No marked differences were found when human and canine systems were compared. Canine preparations could be used for analysis of the S-A node vascularization because of their similarity to the human heart. These findings are clinically relevant to the S-A node dysfunction that may follow cardiac surgical procedures. Surgeons should be aware that there is considerable variation in the exact anatomy of the arterial supply of the S-A node which might be important for cardiological examination and treatment (cardiac surgery, coronary angiography, etc.).

Clinical importance of intramural blood vessels in the sino-atrial segment of the conducting system of the heart

Clinical importance of intramural blood vessels in the sino-atrial segment of the conducting system of the heart

Enrichment of G protein α-subunit mRNAs in the AV-conducting system of the mammalian heart

We investigated the expression pattern of the heterotrimeric G proteins Gs alpha, Gi alpha-2 and Go alpha in rat and guinea-pig heart by in situ hybridization. Cryosections were hybridized with single-stranded 35S-cRNA probes complementary to subtype-specific sequences of the respective mRNAs. Hybridization signals were visualized by exposition to X-ray films and dipping autoradiography. The rank order of abundance was Gi alpha-2 approximately Gs alpha >> Go alpha. In general, G protein alpha-subunit mRNAs were evenly distributed in the heart including endo- and epicardium, large vessels and valves. Go alpha-mRNA levels were significantly higher in atria than in ventricles. In contrast to the rather uniform labeling of working myocardium, expression of all three G proteins was enriched in small intramural blood vessels and in subendocardial Purkinje fibers of septum and papillary muscles. A more marked enrichment of Gs alpha-, Gi alpha-2- and especially Go alpha-mRNA was seen in neuronal ganglionic cells in the atrial septum and posterior regions of the atrium. The main finding, however, was an enrichment of all three G protein mRNAs in the atrioventricular conductive tissue. The accumulation was strictly co-localized with acetylcholinesterase-positive regions identified as the atrioventricular node, the bundle of His and the right and left bundle branches and was seen similarly in rat and guinea-pig hearts. Quantitative in situ hybridization revealed Gs alpha-, Gi alpha-2- and Go alpha-mRNA levels in the bundle of His to be 206 +/- 0.13%. 191 +/- 0.15% and 165 +/- 0.06%, respectively, of that in the surrounding interventricular working myocardium. These findings indicate that heterotrimeric G proteins play an important role in modulation of electrical conductance in the heart.

Crohn's disease: Pathogenesis and persistent measles virus infection

The Inflammatory Bowel Disease Study Group at the Royal Free Hospital School of Medicine has tested the hypothesis that the primary pathological abnormality in Crohn's disease is in the mesenteric blood supply. Early morphological studies involved arterial perfusion-fixation and either resin casting and scanning electron microscopy or vascular immunostaining of resected intestine affected by Crohn's disease. Granulomatous and lymphocytic damage to intramural blood vessels, even in macroscopically normal areas, was observed. We put forward possible mechanisms by which a chronic ischemic process might account for many of the idiosyncracies of Crohn's disease. It was proposed that persistent viral infection of the mesenteric microvascular endothelium might underly this vasculitic process; based on certain behavioral characteristics of measles virus, including its tropism for the submucosal endothelium of the intestine, this agent was investigated further. This report reviews the preliminary evidence from both epidemiological and basic scientific data for persistent measles virus in the intestine of patients with Crohn's disease. Possible mechanisms for virus persistence and subsequent reactivation are discussed. In conclusion, we believe that Crohn's disease may be a chronic granulomatous vasculitis in reaction to a persistent infection with measles virus within the vascular endothelium. This granulomatous inflammation, perhaps aggravated by either a hypercoagulable state or mechanical stress, results in the clinical features of Crohn's disease.

Nitric oxide synthase-containing nerve fibers and neurons in the genital tract of the female mouse.

Nitric oxide (NO) is generated intracellularly from L-arginine by the action of the enzyme nitric oxide synthase (NOS). The present investigation demonstrates immunoreactivity against NOS and nicotinamide adenine dinucleotide phosphate (NADPH)-diaphorase activity in nerve cells and fibers of the reproductive system of the female mouse. The density of nerve fibers staining for NOS varied among different genital organs. The ovary and Fallopian tube were devoid of NOS-positive nerves. The uterine horns received sparse innervation by NOS-containing nerve fibers. The most abundant NOergic innervation was found in the uterine cervix and vagina, where the nerve fibers ran parallel to the smooth muscle bundles and beneath the epithelium; they also accompanied intramural blood vessels. The vaginal muscular wall contained single or groups of NOS-reactive nerve cells. Clusters of NOS-containing neurons were located in Frankenhäuser's ganglion at the cervico-vaginal junction. NO may therefore act as a transmitter in the nervous control of the female reproductive tract.

Calcitonin gene-related peptide: a sensory and motor neurotransmitter in the feline lower esophageal sphincter

The effect of calcitonin gene-related peptide (CGRP) on the feline lower esophageal sphincter (LES) was determined and correlated with its anatomic distribution as determined by immunohistochemistry. Intraluminal pressures of the esophagus and LES were recorded in anesthetized cats. In separate cats, gastroesophageal junctions were removed after locating the LES manometrically and stained for CGRP-like immunoreactivity (LI) and substance P-LI (SP-LI) by indirect immunohistochemistry. CGRP-LI in the LES was most prominent in large nerve fascicles between the circular and longitudinal muscle layers and only rarely seen in nerve fibers within the circular muscle. The myenteric plexus contained numerous CGRP-LI nerve fibers but cell bodies were not seen. Many CGRP-LI nerve fibers in the myenteric plexus and occasional varicose nerves in the circular muscle demonstrated colocalization with SP-LI. Colocalization of CGRP-LI with SP-LI was also seen in the perivascular nerves of the submucosal and intramural blood vessels and in varicose fibers in the lamina propria of the gastric fundic mucosa. In the esophagus, CGRP-LI nerves extended through the muscularis mucosa and penetrated the squamous epithelium to the lumen. CGRP, given intra-arterially, caused a dose-dependent fall in basal LES pressure, with a threshold dose of 10 −8 g/kg (2.63 pmol/kg). At the maximal effective dose, 5 × 10 −6 g/kg (1.31 × 10 3 pmol/kg), CGRP produced 61.0 ± 6.0% decrease in basal LES pressure. At this dose, mean systemic blood pressure fell by 40.9 ± 7.8%. The LES relaxation induced by a submaximal dose of CGRP (10 −6 g/kg, 262.7 pmol/kg), 50.3 ± 3.2% relaxation was partially inhibited by tetrodotoxin (26.9 ± 10.8% relaxation, P < 0.025). The inhibitory effect of CGRP was not affected by cervical vagotomy, hexamethonium, atropine, propranolol, or naloxone. The LES contractile response to the D 50 of SP (5 × 10 −8 g/kg, 37.1 pmol/kg) was not altered by CGRP 10 −8 or 10 −6 g/kg and the CGRP relaxation effect was not altered by the threshold dose of substance P (5 × 10 −9 g/kg, 3.71 pmol/kg). Conclusions: (1) CGRP-LI is present at the feline LES and is primarily seen in large nerve fascicles which pass from the intermuscular plane and through the circular muscle layer to the submucosa and in mucosal nerves. (2) CGRP colocalizes with SP-LI in some varicose nerve fibers of the circular muscle of the esophagus, LES and fundus, in perivascular nerves of the submucosal and intramucosal blood vessels, and in nerves of the lamina propria of the gastric fundus. (3) The luminal penetration of CGRP-LI nerves in the squamous mucosa of the esophagus suggests a sensory function for some CGRP-LI nerves. (4) CGRP exerts a dose-dependent inhibitory effect at the LES by both a neural and a direct smooth muscle effect. (5) Despite colocalization in nerve fibers in the muscularis propria at the LES, CGRP exerts no influence on SP-induced LES contractions.

Distribution of substance P in the enteric plexuses of the small intestine of the platypus, Ornithorhynchm anatinus

A study was made of substance P-like-immunoreactive nerves within the small intestine of platypus, an Australian prototherian mammal. Both immunoreactive nerve cell bodies and fibers were present. No immunoreactive fibers were found in mesenteric nerves or on intramural blood vessels, suggesting that extrinsic sensory neurons containing substance P do not innervate platypus ileum. This was further supported by the result of in vitro experiments. Although applied substance P (10(-9) M-3 x 10(-8) M) caused contraction of the longitudinal muscle, neither mesenteric nerve stimulation nor application of capsaicin caused contractions.

An immunohistochemical study of serotonin-containing nerves in the colon of rats.

The localization of the serotonin-like immunoreactive nerves of the rat colon was investigated by means of immunohistochemistry, utilizing an antibody against serotonin. In non-treated colons, serotonin-positive neuropils were consistently detected around the myenteric plexus. In pargyline-treated colons, serotonin-like fibres were demonstrated in association with either the small intramural blood vessels of the submucosa or the extramural nerve bundles. Treatment with 5-hydroxytryptophan (5-HTP) permitted the visualization of additional serotonin-immunoreactive fibres around the large extramural blood vessels. Immunoreactive nerve cell bodies were demonstrated in the myenteric plexus of colons treated with 5-HTP or colchicine. From these observations, it is suggested that the serotoninergic nerves of the rat colon comprise both intrinsic and extrinsic elements.