Mechanisms underlying intracisternal TRH-induced stimulation of gastric acid secretion in rats

The neurohumoral pathways mediating intracisternal TRH-induced stimulation of gastric acid secretion were investigated. In urethane-anesthetized rats, with gastric and intrajugular cannulas, TRH or the analog [N-Val2]-TRH (1 microgram) injected intracisternally increased gastric acid output for 90 min. Serum gastrin levels were not elevated significantly. Under these conditions the TRH analog, unlike TRH, was devoid of thyrotropin-releasing activity as measured by serum TSH levels. In pylorus-ligated rats, gastrin values were not modified 2 h after peptide injection whereas gastric acid output was enhanced. TRH (0.1-1 micrograms) stimulated vagal efferent discharge, recorded from a multifiber preparation of the cervical vagus in urethane-anesthetized rats and the response was dose-dependent. The time course of vagal activation was well correlated with the time profile of gastric stimulation measured every 2 min. These results demonstrated that gastric acid secretory stimulation elicited by intracisternal TRH is not related to changes in circulating levels of gastrin or TSH but is mediated by the activation of efferent vagal pathways that stimulated parietal cell secretion.     

Central nervous system action of TRH to stimulate gastric emptying in rats

The effects of intracisternal injection of TRH on gastric emptying of a liquid meal was investigated in 24 h fasted rats using the phenol red method. Intracisternal injection of TRH, RX 77368, or [N-Val2]-TRH, an analog devoid of TSH-releasing activity, 5 min prior to a meal, stimulated gastric emptying measured 20 min later. TRH action was dose dependent (1-100 ng), and rapid in onset. The calculated time for emptying half of the meal was decreased from 16 +/- 3 min (control group) to 4 +/- 1 min (TRH 30 ng). The stable analog, RX 77368, unlike TRH, stimulated gastric emptying when the meal was given 60 min after peptide injection. Intravenous injection of atropine (2.5 micrograms) inhibited and that of carbachol (1 microgram) stimulated gastric emptying whereas i.v. injection of TRH (0.1-1 microgram) had no effect. Vagotomy but not adrenalectomy reversed the increase in gastric emptying induced by intracisternal TRH. Atropine blocked the stimulatory effect of TRH and carbachol. These results demonstrate that TRH acts within the brain to stimulate gastric emptying through vagus-dependent and cholinergic pathways whereas alterations of adrenal and pituitary-thyroid secretion do not play an important role.     

Calcitonin gene-related peptide acts within the central nervous system to inhibit gastric acid secretion

The central nervous system effect of calcitonin gene-related peptide (CGRP) on gastric acid secretion was studied in conscious freely moving rats. CGRP (220 fmol to 2.2 nmol) injected into the lateral cerebral ventricle or intravenously inhibited gastric acid secretion. Intravenous passive immunization with CGRP antiserum prevented the inhibitory effect of CGRP following intravenous but not intracerebroventricular administration. Adrenalectomy and noradrenergic blockade with bretylium tosylate did not significantly alter the inhibitory action of CGRP given intracerebroventricularly on gastric secretion. These studies indicate that CGRP acts within the central nervous system to potently decrease gastric acid secretion by mechanism(s) not dependent on intact sympathetic nervous function.     

Central action of somatostatin analog, SMS 201-995, to stimulate gastric acid secretion in rats

The effects of intracisternal and intravenous injections of the somatostatin analog, SMS 201-995, on gastric acid secretion were investigated in rats with pylorus ligation or gastric cannula. Intracisternal injection of SMS 201-995 induced a dose-related (0.1-0.3 microgram) and long-lasting stimulation of gastric acid output with a peak response at 3 h postinjection in conscious, pylorus-ligated rats. Intracisternal SMS 201-995 increased histamine levels in the portal blood, whereas plasma gastrin levels were not modified. Atropine, cimetidine and adrenalectomy abolished the stimulatory effect of intracisternal SMS 201-995 (0.3 microgram). SMS 201-995 (0.03 microgram), microinjected unilaterally into the dorsal vagal complex, increased gastric acid output in urethane anesthetized rats. SMS 201-995, injected intravenously at 0.5 microgram, did not alter gastric secretion, whereas higher doses (5-20 micrograms) resulted in a dose-related inhibition of gastric acid secretion in conscious pylorus-ligated rats. These data indicate that SMS 201-995, a selective ligand for somatostatin-1 receptor subtype, induces a centrally mediated stimulatory effect on gastric acid secretion in rats. The central action involves the parasympathetic system, muscarinic and H2 receptors as well as adrenal-dependent pathways.     

Effect of probiotics and triple eradication therapy on the cyclooxygenase (COX)-2 expression, apoptosis, and functional gastric mucosal impairment in Helicobacter pylori-infected Mongolian gerbils

BACKGROUND: Helicobacter pylori infection in Mongolian gerbils is an established experimental model of gastric carcinogenesis that mimics H. pylori-positive patients developing gastric ulcer and gastric cancer, but the effect of probiotic therapy on functional aspects of this infection remains unknown. METHODS: We compared the effects of intragastric inoculation of gerbils with H. pylori strain (cagA+ vacA+, 5 x 10(6) colony forming units/ml) with or without triple therapy including omeprazole, amoxicillin, and tinidazol or probiotic bacteria Lacidofil. Histology of glandular mucosa, the viable H. pylori, and density of H. pylori colonization were evaluated. The gastric blood flow was measured by H2-gas clearance method; the plasma gastrin and gastric luminal somatostatin were determined by RIA and expression of cyclooxygenase (COX)-2 and apoptotic Bax and Bcl-2 proteins were evaluated by Western blot. RESULTS: The gastric H. pylori infection was detected in all animals by histology and H. pylori culture. Basal gastric acid was significantly reduced in H. pylori-infected animals but not in those with triple therapy or Lacidofil. Early lesions were seen already 4 weeks upon H. pylori inoculation and consisted of chronic gastritis and glandular atypia associated with typical regenerative hyperplasia and increased mitotic activity and formation of apoptotic bodies. The H. pylori infection was accompanied by the fall in gastric blood flow, the marked increase in plasma gastrin, the significant fall in gastric somatostatin levels and Bcl-2 protein expression, and the rise in expression of COX-2 and Bax proteins. These mucosal changes were counteracted by the triple therapy and Lacidofil. CONCLUSIONS: H. pylori infection in gerbils, associated with regenerative hyperplasia of glandular structure, results in the suppression of gastric secretion, overexpression of COX-2, and enhancement in apoptosis and impairment of both, gastric blood flow and gastrin-somatostatin link that were reversed by anti-H. pylori triple therapy and attenuated by probiotics.     

Phe-X-Pro-Arg-Leu-NH(2) peptide producing cells in the central nervous system of the silkworm,Bombyx mori

Members of the neuropeptide family having Phe-X-Pro-Arg-Leu-NH(2) (FXPRLamide; X=Ser, Thr, Val, or Gly) at the C-terminus serve as regulators of oviduct and visceral muscle contraction, sex pheromone production, and diapause induction. Antibody raised against Bombyx mori diapause hormone recognized a variety of FXPRLamide peptides. Using this antibody, the antigen was immunocytochemically localized in the central nervous system (CNS) of the silkworm, Bombyx mori. Immunoreactive somata were observed in all ganglia of the CNS including the brain. Twelve somata localized at the midline of the suboesophageal ganglion (SG) were most intensely stained, and their neurite projections reached the retrocerebral complex. Thus, these cells in the SG exhibited typical features of neuroendocrine neurons. Marked reduction in immunoreactivity was observed in a pair of neurosecretory cells in the labial neuromere in SG of diapause type pupae, which indicates an active release of FXPRLamide peptides from these cells. No clear connection to neurohemal sites were observed in immunoreactive cells in the brain, thoracic or abdominal ganglia, suggesting that the immunoreactive peptides in these organs are likely to serve as neurotransmitters or neuromodulators.     

Glucagon-like peptide (GLP)-2 action in the murine central nervous system is enhanced by elimination of GLP-1 receptor signaling

Glucagon-like peptide-2 (GLP-2) regulates energy homeostasis via effects on nutrient absorption and maintenance of gut mucosal epithelial integrity. The biological actions of GLP-2 in the central nervous system (CNS) remain poorly understood. We studied the sites of endogenous GLP-2 receptor (GLP-2R) expression, the localization of transgenic LacZ expression under the control of the mouse GLP-2R promoter, and the actions of GLP-2 in the murine CNS. GLP-2R expression was detected in multiple extrahypothalamic regions of the mouse and rat CNS, including cell groups in the cerebellum, medulla, amygdala, hippocampus, dentate gyrus, pons, cerebral cortex, and pituitary. A 1.5-kilobase fragment of the mouse GLP-2R promoter directed LacZ expression to the gastrointestinal tract and CNS regions in the mouse that exhibited endogenous GLP-2R expression, including the cerebellum, amygdala, hippocampus, and dentate gyrus. Intracerebroventricular injection of GLP-2 significantly inhibited food intake during dark-phase feeding in wild-type mice. Disruption of glucagon-like peptide-1 receptor (GLP-1R) signaling with the antagonist exendin-(9-39) in wild-type mice or genetically in GLP-1R(-)/- mice significantly potentiated the anorectic actions of GLP-2. These findings illustrate that CNS GLP-2R expression is not restricted to hypothalamic nuclei and demonstrate that the anorectic effects of GLP-2 are transient and modulated by the presence or absence of GLP-1R signaling in vivo.     

Epidermal growth factor as a local mediator of the neurotrophic action of vitamin B(12) (cobalamin) in the rat central nervous system.

We have recently demonstrated that the myelinolytic lesions in the spinal cord (SC) of rats made deficient in vitamin B(12) (cobalamin) (Cbl) through total gastrectomy (TG) are tumor necrosis factor-alpha (TNF-alpha)-mediated. We investigate whether or not permanent Cbl deficiency, induced in the rat either through TG or by chronic feeding of a Cbl-deficient diet, might modify the levels of three physiological neurotrophic factors-epidermal growth factor (EGF), vasoactive intestinal peptide (VIP), and somatostatin (SS)-in the cerebrospinal fluid (CSF) of these rats. We also investigated the ability of the central nervous system (CNS) in these Cbl-deficient rats to synthesize EGF mRNA and of the SC to take up labeled Cbl in vivo. Cbl-deficient rats, however the vitamin deficiency is induced, show a selective decrease in EGF CSF levels and an absence of EGF mRNA in neurons and glia in various CNS areas. In contrast, radiolabeled Cbl is almost exclusively taken up by the SC white matter, but to a much higher degree in totally gastrectomized (TGX) rats. Chronic administration of Cbl to TGX rats restores to normal both the EGF CSF level and EGF mRNA expression in the various CNS areas examined. This in vivo study presents the first evidence that the neurotrophic action of Cbl in the CNS of TGX rats is mediated by stimulation of the EGF synthesis in the CNS itself. It thus appears that Cbl inversely regulates the expression of EGF and TNF-alpha genes in the CNS of TGX rats.     

Accumulation of N-acetyl-L-aspartate in the brain of the tremor rat, a mutant exhibiting absence-like seizure and spongiform degeneration in the central nervous system

The tremor rat is a mutant that exhibits absence-like seizure and spongiform degeneration in the CNS. By positional cloning, a genomic deletion was found within the critical region in which the aspartoacylase gene is located. Accordingly, no aspartoacylase expression was detected in any of the tissues examined, and abnormal accumulation of N-acetyl-L-aspartate (NAA) was shown in the mutant brain, in correlation with the severity of the vacuole formation. Therefore, the tremor rat may be regarded as a suitable animal model of human Canavan disease, characterized by spongy leukodystrophy that is caused by aspartoacylase deficiency. Interestingly, direct injection of NAA into normal rat cerebroventricle induced 4- to 10-Hz polyspikes or spikewave-like complexes in cortical and hippocampal EEG, concomitantly with behavior characterized by sudden immobility and staring. These results suggested that accumulated NAA in the CNS would induce neuroexcitation and neurodegeneration directly or indirectly.     

A novel GLP-1 analog,a dimer of GLP-1 via covalent linkage by a lysine,prolongs the action of GLP-1 in the treatment of type 2 diabetes

GLP-1 is an incretin hormone that can effectively lower blood glucose, however, the short time of biological activity and the side effect limit its therapeutic application. Many methods have been tried to optimize GLP-1 to extend its in vivo half-time, reduce its side effect and enhance its activity. Here we have chosen the idea to dimerize GLP-1 with a C-terminal lysine to form a new GLP-1 analog, DLG3312. We have explored the structure and the biological property of DLG3312, and the results indicated that DLG3312 not only remained the ability to activate the GLP-1R, but also strongly stimulated Min6 cell to secrete insulin. The in vivo bioactivities have been tested on two kinds of animal models, the STZ induced T2DM mice and the db/db mice, respectively. DLG3312 showed potent anti-diabetic ability in glucose tolerance assay and single-dose administration of DLG3312 could lower blood glucose for at least 10 hours. Long-term treatment with DLG3312 can reduce fasted blood glucose, decrease water consumption and food intake and significantly reduce the HbA1c level by 1.80% and 2.37% on STZ induced T2DM mice and the db/db mice, respectively. We also compared DLG3312 with liraglutide to investigate its integrated control of the type 2 diabetes. The results indicated that DLG3312 almost has the same effect as liraglutide but with a much simpler preparation process. In conclusion, we, by using C-terminal lysine as a linker, have synthesized a novel GLP-1 analog, DLG3312. With simplified preparation and improved physiological characterizations, DLG3312 could be considered as a promising candidate for the type 2 diabetes therapy.     

Sarco-endoplasmic reticulum Ca2+ ATPase (SERCA) inhibitors identify a novel calcium pool in the central nervous system

Ca2+ uptake into the endoplasmic reticulum (ER) is mediated by Ca2+ ATPase isoforms, which are all selectively inhibited by nanomolar concentrations of thapsigargin. Using ATP/Mg2+-dependent 45Ca2+ transport in rat brain microsomes, tissue sections, and permeabilized cells, as well as Ca2+ imaging in living cells we distinguish two ER Ca2+ pools in the rat CNS. Nanomolar levels of thapsigargin blocked one component of brain microsomal 45Ca2+ transport, which we designate as the thapsigargin-sensitive pool (TG-S). The remaining component was only inhibited by micromolar thapsigargin, and thus designated as thapsigargin resistant (TG-R). Ca2+ ATPase and [32P]phosphoenzyme assays also distinguished activities with differential sensitivities to thapsigargin. The TG-R Ca2+ uptake displayed unique anion permeabilities, was inhibited by vanadate, but was unaffected by sulfhydryl reduction. Ca2+ sequestered into the TG-R pool could not be released by inositol-1,4,5-trisphosphate, caffeine, or cyclic ADP-ribose. The TG-R Ca2+ pool had a unique anatomical distribution in the brain, with selective enrichment in brainstem and spinal cord structures. Cell lines that expressed high levels of the TG-R pool required micromolar concentrations of thapsigargin to effectively raise cytoplasmic Ca2+ levels. TG-R Ca2+ accumulation represents a distinct Ca2+ buffering pool in specific CNS regions with unique pharmacological sensitivities and anatomical distributions.     

Pituitary response to growth hormone-releasing factor in rats with functional or anatomical lesions of the central nervous system that inhibit endogenous growth hormone secretion

The pituitary growth hormone (GH) response to the growth hormone-releasing factor, hpGRF-44, was evaluated in male rats with various lesions of the central nervous system. These included an electrical lesion of the ventromedial hypothalamus, a chemical lesion of the arcuate nucleus induced by neonatal treatment with monosodium glutamate, a functional lesion of catecholamine synthesis with alpha-methyl-p-tyrosine or a functional lesion of catecholamine storage with reserpine. The first three lesions appear to partially inhibit normal somatostatin secretion since in every instance hpGRF-44 administration induced a significant increase in plasma GH concentrations. In contrast, reserpine blocked the GH response to hpGRF-44, presumably by stimulating somatostatin secretion. The pituitary GH response to hpGRF-44 in the above described models was enhanced by pretreatment of the rats with antibodies against somatostatin. The pituitary GH response to repeated injections of hpGRF-44 was also evaluated in rats with an anatomical lesion of the arcuate nucleus or a functional lesion of catecholamine synthesis. The maximum GH response did not vary over time to the repeated injections of hpGRF-44 in rats with lesions of the arcuate nucleus; however, interruption of catecholamine synthesis resulted in a significant decrease in the GH response to hpGRF-44 over time.     

Expression of a medaka (Oryzias latipes) Bar homologue in the differentiating central nervous system and retina

Endoglin is an auxiliary receptor for the transforming growth factor-β family of cytokines and is required for angiogenesis and heart development. Endoglin expression during mouse embryogenesis was analysed by monitoring β-galactosidase expression from a lacZ reporter cassette inserted downstream of the endoglin promoter. Expression was first detected at 6.5 days post-coitum (dpc) in the amniotic fold and developing allantois. Between 7.5 and 8.5 dpc, endoglin was expressed in endothelial cells of the yolk sac, dorsal aorta and primitive heart tube, and from 9.5 to 13.5 dpc in endothelial cells throughout the developing vasculature. Interestingly, this pattern of endoglin expression is almost identical to that reported for Alk1.     

Approach to a social stranger is associated with low central nervous system serotonergic responsivity in female cynomolgus monkeys (Macaca fascicularis)

It is widely hypothesized that individual differences in central nervous system (CNS) serotonergic activity underlie dimensional variation in "impulsive" vs. "inhibited" social behavior in both humans and nonhuman primates. To assess relative impulsivity in a social context, a behavioral challenge involving animals' exposure to a social stranger (termed the "Intruder Challenge") was recently validated in adolescent and adult male vervet monkeys (Cercopithecus aethiops sabaeus). Among these animals, monkeys that quickly approached the intruder were found to have lower cerebrospinal fluid (CSF) concentrations of the serotonin (5-HT) metabolite, 5-hydroxyindoleacetic acid, than less impulsive animals. In the present study we extended these observations to determine whether approach to a social stranger, as operationalized by the Intruder Challenge, is similarly associated with diminished CNS serotonergic function in female cynomolgus monkeys (Macaca fascicularis). Study animals were 25 adult monkeys that had been housed for 2 years in stable social groups. In each animal, the rise in plasma prolactin concentration induced by acute administration of the 5-HT agonist, fenfluramine, was used to assess "net" central serotonergic responsivity. When exposed later to an unfamiliar female of the same species in a catch-cage placed for 20 min within the subjects' home enclosure, monkeys that approached to within 1 m of the intruder (median latency to approach=3 min) were found to have significantly smaller prolactin responses to fenfluramine (diminished serotonergic responsivity) compared to "inhibited" animals that failed to approach the intruder (t=2.9, df=23, P<0.009; rpb=-0.51). Neither approach behavior nor the animals' fenfluramine-induced prolactin responses covaried significantly with nondirected expressions of arousal (or anxiety) or with aggressive behaviors exhibited during testing. We conclude that in female cynomolgus monkeys, social impulsivity (vs. inhibition) correlates inversely with individual differences in CNS serotonergic activity, as assessed by neuroendocrine challenge.     

A polymorphism detected in a variable number of tandem repeats (VNTR) of the seminal vesicle secretion (SVS) IV gene in inbred rats

The second intron of the rat SVS IV gene contains a tandem repeat region of 20-bp sequences. This region was amplified using the polymerase chain reaction to detect variations. Three alleles, characterized by amplified fragments of 750, 490, and 390 bp, respectively, were found in 24 strains examined. This variation segregated in F₁ and backcross progeny in an autosomal codominant manner. We tentatively designated this locusSvs-4. Analysis of linkages between theSvs-4 locus and other loci revealed that it was closely linked to theSvp-1 (<2.9%) and the a (10.0±6.7%) loci, which belong to rat linkage group IV. TheSvp-1 andSvs-4 loci, however, were differently distributed among the inbred rat strains.This work was supported by a Grant-in-Aid for Scientific Research from the Ministry of Education, Science and Culture of Japan.     

Lipocalin-2 Is a chemokine inducer in the central nervous system: role of chemokine ligand 10 (CXCL10) in lipocalin-2-induced cell migration

The secreted protein lipocalin-2 (LCN2) has been implicated in diverse cellular processes, including cell morphology and migration. Little is known, however, about the role of LCN2 in the CNS. Here, we show that LCN2 promotes cell migration through up-regulation of chemokines in brain. Studies using cultured glial cells, microvascular endothelial cells, and neuronal cells suggest that LCN2 may act as a chemokine inducer on the multiple cell types in the CNS. In particular, up-regulation of CXCL10 by JAK2/STAT3 and IKK/NF-κB pathways in astrocytes played a pivotal role in LCN2-induced cell migration. The cell migration-promoting activity of LCN2 in the CNS was verified in vivo using mouse models. The expression of LCN2 was notably increased in brain following LPS injection or focal injury. Mice lacking LCN2 showed the impaired migration of astrocytes to injury sites with a reduced CXCL10 expression in the neuroinflammation or injury models. Thus, the LCN2 proteins, secreted under inflammatory conditions, may amplify neuroinflammation by inducing CNS cells to secrete chemokines such as CXCL10, which recruit additional inflammatory cells.     

Distribution of 5-HT (serotonin) immunoreactivity in the central nervous system of the inshore hagfish,Eptatretus burgeri

Summary Immunohistochemical techniques were used to study the distribution of serotonin in the central nervous system of the hagfish,Eptatretus burgeri, in order to produce a detailed map of serotonin-containing structures. In the hypothalamus, many serotonin-containing neurons contacted the cerebrospinal fluid. Most of the serotonin-containing cell bodies were located in the raphe region, where they were compactly distributed at the level of the nucleus motorius tegmenti pars anterior but more diffusely distributed at the level of the nucleus motorius tegmenti pars posterior. Serotonin-containing cell bodies and varicose fibers were widely distributed throughout the brain and upper spinal cord segments, but the distribution density was not even. On the basis of its abundance, serotonin can be judged to have an important function in the control of the hagfish central nervous system. From a phylogenetic point of view, serotonin-containing neurons in the raphe region appear to be a common property of all classes of vertebrates studied except the lampreys, whereas serotonin-containing cerebrospinal fluid-contacting neurons may be considered to be a primitive condition in all nonmammalian vertebrates.