Changes in the afferent activity of the vagus nerve and the rectal temperature in rats following Escherichia coli endotoxin administration]

In anaesthetised rats, i.p. administration of the Echerichia coli lipopolysaccharide in doses 5 mcg/kg (LPS) increased afferent activity of the cervical vagus, whereas 100 and 1000 mcg/kg doses inhibited the afferent discharges. Pyrogen-free saline (PFS) did not alter the activity. Rectal temperature (RT) was decreased by the PFS and by large doses of the LPS. Sodium salicylate administration prevented the effects.     

Role of the vagus nerve in mechanisms of the modulation of afferent duodenal effects]

The electrostimulation of vagal nerves, the effect of naloxone and atropine on duodenal afferentation by registering evoked potential (EP) at cortex on direct electrostimulation of duodenum have been studied in acute experiments on cats. It has been established that the stimulation of afferent portion of vagal nerves causes the effect of deprivation of EP, whereas the stimulation with certain intensity of efferent portion of vagal nerves intensifies the duodenal afferentation. The effect of afferentation easeness (relief) has been blocked by the application of naloxone 10-20 microgram on duodenal bulbus, but not on it's i. v. injection and without effect on local application of atropine. It is concluded that the role of vagal nerves on the modulation of duodenal nociception is due to the activation of opiate terminals of the efferent vagal nerve portions.     

Assessment of th- quantity of mast cells in the organs of the gastrointestinal tract of rats and frogs]

A method of evaluation of mast cell concentration in which all the tissues of an organ are included gives statistically significant figures. This method showed mast cell concentration in the digestive tract organs of rats and frogs to be a fixed value within a morphofunctional zone. In the tongue the mast cell concentration was the same both along its length and in the symmetrical parts of the organ. The concentration of mast cells diminished considerably from the tongue, the duodenum and down to the stomach.     

Investigation of peptide stability upon hydrolysis by of fragments of the organs of the gastrointestinal tract of rats

The hydrolytic stability of a range of cyclic tripeptides, including the therapeutically important dalargin and stemokin, as well as peptides modified by ibuprofen and aspirin, has been studied. The first two experimental systems used utilized purified enzymes (pepsin, trypsin, and chymotrypsin), while the second one utilized fragments of the stomach and small intestine of rats. The linear peptides containing only L-amino acid residues were shown to be hydrolyzed by stomach and intestine fragments, although some of these peptides were resistant to hydrolysis by individual enzymes. The peptides containing D-amino acid residues and cyclic peptides were stable under all of the conditions used, but the peptides modified by aspirin lost the acetyl group of the aspirin moiety in acidic media, this process being accelerated in the presence of pepsin.     

Purinergic signalling in the gastrointestinal tract and related organs in health and disease

Purinergic signalling plays major roles in the physiology and pathophysiology of digestive organs. Adenosine 5′-triphosphate (ATP), together with nitric oxide and vasoactive intestinal peptide, is a cotransmitter in non-adrenergic, non-cholinergic inhibitory neuromuscular transmission. P2X and P2Y receptors are widely expressed in myenteric and submucous enteric plexuses and participate in sympathetic transmission and neuromodulation involved in enteric reflex activities, as well as influencing gastric and intestinal epithelial secretion and vascular activities. Involvement of purinergic signalling has been identified in a variety of diseases, including inflammatory bowel disease, ischaemia, diabetes and cancer. Purinergic mechanosensory transduction forms the basis of enteric nociception, where ATP released from mucosal epithelial cells by distension activates nociceptive subepithelial primary afferent sensory fibres expressing P2X3 receptors to send messages to the pain centres in the central nervous system via interneurons in the spinal cord. Purinergic signalling is also involved in salivary gland and bile duct secretion.     

Electrical stimulation of afferent vagus nerve induces IL-1beta expression in the brain and activates HPA axis

Possible roles of the afferent vagus nerve in regulation of interleukin (IL)-1beta expression in the brain and hypothalamic-pituitary-adrenal (HPA) axis were examined in anesthetized rats. Levels of IL-1beta mRNA and protein in the brain were measured by comparative RT-PCR and ELISA. Direct electrical stimulation of the central end of the vagus nerve was performed continuously for 2 h. The afferent stimulation of the vagus nerve induced increases in the expression of mRNA and protein levels of IL-1beta in the hypothalamus and the hippocampus. Furthermore, expression of corticotropin-releasing factor mRNA was increased in the hypothalamus 2 h after vagal stimulation. Plasma levels of ACTH and corticosterone were also increased by this stimulation. The present results indicate that activation of the afferent vagus nerves itself can induce production of IL-1beta in the brain and activate the HPA axis. Therefore, the afferent vagus nerve may play an important role in transmitting peripheral signals to the brain in the infection and inflammation.     

Reaction of the hypothalamo-hypophyseal system of cats to stimulation of the cervical sympathetic nerve and the afferent fibers of the vagus nerve]

Data are presented on the functional morphology of the hypothalamo-hypophysial neurosecretory system of cats in stimulation of the cervical sympathetic nerve and of the afferent fibers of the vagus. Stimulation of the sympathetic nerve selectively activated the supraoptic nucleus and caused the discharge of the neurohormones from the posterior lobe of the hypophysis, whereas its infundibular portion contained much neurosecretory material. In response to the stimulation of the vagus all the portions of the neurohypophysis were released of the Gomori-positive substance; both the supraoptic and the paraventricular nucleus were activated.     

Microbiocenosis of parietal mucin in the gastrointestinal tract of rats

The qualitative and quantitative composition of the microbial community in parietal mucin at different areas of the gastrointestinal tract (GIT) of rats was revealed. The pronounced variability in the quantitative and qualitative characteristics of microbiocenosis in parietal mucin of rats at different sections was revealed. The differences were most pronounced in the passage from upper to lower GIT sections, the large intestine found to be the richest biocenosis. The microbial composition of rat feces was faintly associated with the GIT parietal microbiocenosis. The individual areas of GIT mucosa were unique of their microbial characteristics and organization. This makes it possible to regard them as relatively independent biotopes and indicates that it is impossible to evaluate the microbial community by one of the colonic mucosal sifes.     

Capsaicin-sensitive afferents in the vagus nerve

Vanilloids were shown to interact with over 70% of vagal C-afferents first causing an excitation followed by desensitisation and a lasting destruction of nerve fibres. Capsaicin induces a secretion of some neuropeptides from 10-30% of vagal sensory terminals and therefore serves as a pharmacological tool for testing local "effector function" of primary afferents. Vagal afferents seem to have their own subtype of vanilloid receptors (VR), not completely identical with the VR receptors in the dorsal root ganglia. Considering potentiation of the capsaicin receptors sensitivity by some factors such as local heating, pH, free oxygen radicals, a possible role of the VRs as integrators of chemical and physical components of nociceptive stimuli, is discussed.     

Myeloarchitectonics of the vagus nerve in man

In serial electively stained transversal sections of the vagus nerve trunk taken at the levels beginning from its exit out of the brain, up to terminal branches in the abdominal cavity (10 corpses of mature persons) myelin fibers of three classes have been counted. Along the course of the nerve trunk in the craniocaudal direction the total number of the myelin fibers decreases. Only about 10% of the initial amount of the myelin conductors revealed at the level of the intracranial part of the vagus nerve get into the abdominal cavity. Simultaneously, the ratio of the myelin fibers belonging to different classes changes: the part of the fine conductors increases, and that of the fibers having middle and large diameters decreases. The most important in the dynamics of the whole amount of myelin fibers and in the number of the conductors belonging to different classes at all the levels of the nerve trunk is the getting off the organs' branches with various functional specialization.     

Distribution of serotonin-immunoreactive nerve cells and fibers in the rat gastrointestinal tract

 The distribution of serotonin-immunoreactive (5HT-IR) nerve cells and fibers was thoroughly investigated immunohistochemically in the rat stomach, duodenum, jejunum, ileum, and colon. The immunoreactivity of the 5HT neurons was compared between non-treated controls and animals treated with colchicine, colchicine plus 5-hydroxytryptophan (5HTP), colchicine plus pargyline, and reserpine. The intensity of immunoreactivity in nerve fibers as well as nerve cell bodies was enhanced mostly in colchicine plus pargyline treated animals, therefore these animals were used for an observation of precise localization of 5HT in the rat gastrointestinal (GI) tract. Immunoreactivity in the nerve cell bodies and fibers was completely abolished in the GI tract of reserpine treated animals. The pattern of localization and projection of 5HT-IR neurons was similar in all segments of the rat GI tract. 5HT-IR nerve cell bodies were located in the myenteric plexus and showed the distinctive features of Dogiel type I neurons. Prominent bundles of varicose fibers traversed the myenteric ganglia and some of them surrounded the cell bodies of immunopositive and immunonegative neurons. 5HT-IR nerve fibers were located in the submucous plexus, densely entwined about the submucosal blood vessels. Most characteristically, 5HT-IR nerve fibers invaded the lamina propria of mucosa where they underlay the crypt epithelium. In conclusion, the present study showed that 5HT-IR neurons located in the myenteric plexus projected fibers widely in the rat GI tract. The localization of fibers in the lamina propria of mucosa implies that this neuron may exert an important role in the epithelial function of the GI tract. Accepted: 8 October 1996     

Vanilloid receptor (VR1) expression in vagal afferent neurons innervating the gastrointestinal tract

The vanilloid receptor VR1 is a nonselective cation channel activated by capsaicin as well as increases in temperature and acidity, and can be viewed as molecular integrator of chemical and physical stimuli that elicit pain. The distribution of VR1 receptors in peripheral and central processes of rat primary vagal afferent neurons innervating the gastrointestinal tract was investigated by immunohistochemistry. Forty-two percent of neurons in the nodose ganglia retrogradely labeled from the stomach wall expressed low to moderate VR1 immunoreactivity (VR1-IR). VR1-IR was considerably lower in the nodose ganglia as compared to the jugular and dorsal root ganglia. In the vagus nerve, strongly VR1-IR fibers ran in separate fascicles that supplied mainly cervical and thoracic targets, leaving only weakly VR1-IR fibers in the subdiaphragmatic portion. Vagal afferent intraganglionic laminar endings (IGLEs) in the gastric and duodenal myenteric plexus did not express VR1-IR. Similarly, VR1-IR was contained in fibers running in perfect register with vagal afferents, but was not colocalized with horseradish peroxidase in the same varicosities of intramuscular arrays (IMAs) and vagal afferent fibers in the duodenal submucosa anterogradely labeled from the nodose ganglia. Only in the gastric mucosa did we find evidence for colocalization of VR1-IR in vagal afferent terminals. In contrast, many nerve fibers coursing through the myenteric and submucosal plexuses contained detectable VR1-IR, the majority of which colocalized calcitonin gene-related peptide immunoreactivity. In the dorsal medulla there was a dense plexus of VR1-IR varicose fibers in the commissural, dorsomedial and gelatinosus subnuclei of the medial NTS and the lateral aspects of the area postrema, which was substantially reduced, but not eliminated on the ipsilateral side after supranodose vagotomy. It is concluded that about half of the vagal afferents innervating the gastrointestinal tract express low levels of VR1-IR, but that presence in most of the peripheral terminal structures is below the immunohistochemical detection threshold.     

Influence of Bacillus cereus on microbiocenosis of gastrointestinal tract in rats

The modifying effect of Bacillus cereus on intestinal microbiocenosis was investigated in eubiotic and disbiotic female rats. Qualitative and quantitative characteristics of gut and mucosal microflora from different parts of rats' intestine were studied before and after intragastral application of B. cereus suspension. The single application of B. cereus suspension resulted in appearance of this bacterium in feces and in parietal mucin from all parts of the intestine. In eubiotic rats compared with disbiotic, B. cereus adhere to parietal mucin much more efficiently and supplanted indigenous microflora. During disbiosis B. cereus sometimes had stimulating effect on the intestinal microbiocenosis. Gut microbiocenosis appeared to be more resistant to B. cereus invasion than mucosal. This fact was considered to be the evidence of higher sensitivity of mucosal microbiocenosis to short-term influence of exogenous microbial factor.     

Effect of ligation of the pancreatic ducts on endogenous serotonin distribution in the organs of the gastrointestinal tract

The content of endogenous serotonin in the mucosa of various parts of the stomach and the small intestine and also in the homogenates of the pancreatic tissue and the peripheral blood was traced in the course of 12 months after the ligation of the pancreatic ducts in dogs. Marked and prolonged disturbances were revealed in the deposition of the endogenous serotonin characterized by definite regularities in all the tissues under study, connected with the changes of the relative constancy of the enteral medium due to the absence of pancreatic secretion in the lumen of the digestive tube.