Intragastric Research Articles

Soy isoflavone affects the autonomic nervous system in a tissue-specific manner in anesthetized rats

We examined and compared the effects of taste stimulation by soy saponin as well as soy isoflavone and intragastric (IG) injection of both on the autonomic nerve activities and feeding behavior in rats. We found that taste stimulation by soy saponin or soy isoflavone-rich solution (SIRS) did not affect the activity of the sympathetic nerve supplying the adrenal gland in urethane-anesthetized rats; however, IG injection of SIRS, but not soy saponin, stimulated the adrenal sympathetic nerve activity (ASNA) in a dose-dependent manner. Moreover, IG injection of SIRS significantly suppressed the activity of the vagus nerve innervating the stomach, whereas sympathetic nerve outflows to brown or white adipose tissue were not affected by IG injection of SIRS. To test the involvement of the afferent autonomic nerve in the abdominal organs for regulation of the efferent ASNA by SIRS, we examined the response of the adrenal sympathetic innervation to SIRS injection in rats with ablated afferent vagus or afferent sympathetic nerves. The activating effect of SIRS on the ASNA was inhibited in sympathectomized rats but not in vagotomized rats. Thus, our data suggest that soy isoflavone might affect tissue-specific autonomic nerves through the afferent sympathetic nerve pathway.

Post-oral fat stimulation of intake and conditioned flavor preference in C57BL/6J mice: A concentration-response study

Fat appetite is determined not only by orosensory (flavor) stimuli but also by the post-oral actions of dietary fat, which promote increased attraction to the flavors of high-fat foods. Experiment 1 presents a concentration-response analysis of how intragastric (IG) fat self-infusions stimulate intake and condition flavor preferences in C57BL/6J mice trained 1h/day. Separate groups of food-restricted mice consumed a flavored saccharin solution (the CS−) paired with IG self-infusions of water (Test 0) followed by a different flavored solution (the CS+) paired with IG self-infusions of 1.6, 3.2, 6.4 or 12.8% Intralipid (IL, soybean oil) (Tests 1–3). Following additional CS− and CS+ training sessions, a two-bottle CS+ vs. CS− choice test was conducted without infusions. Infusions of 3.2–12.8% IL stimulated CS+ licking in the first test session and more so in subsequent test sessions, and also conditioned significant CS+ preferences. These effects were similar to those previously observed with isocaloric glucose infusions (8–32%). IG infusion of 1.6% IL stimulated intake slightly but did not condition a CS+ preference comparable to the actions of isocaloric 4% glucose. Experiment 2 compared these subthreshold IL and glucose concentrations with that of a 1.6% IL+4% glucose infusion. This mixture stimulated 1-h CS+ licking more rapidly but generated a preference similar to that of 1.6% IL. In 23h/day tests, however, the IL+glucose mixture stimulated greater CS+ intakes and preferences than did 1.6% IL or 4% glucose. These findings show that fat, like glucose, rapidly generates concentration-dependent post-oral signals that stimulate intake and enhance preferences for energy-rich foods in mice.

Injection of Lactobacillus casei strain Shirota affects autonomic nerve activities in a tissue-specific manner, and regulates glucose and lipid metabolism in rats.

Previously, it was observed that long-term ingestion of a probiotic strain Lactobacillus casei Shirota (LcS) ameliorates insulin resistance and glucose intolerance in rats fed a high-fat diet. In the present study, we examined its possible role in the autonomic nervous system during LcS-induced modulations in glucose and lipid metabolism or cardiovascular functions. The present study examined the effects of intragastric (IG) LcS injection on autonomic nerve tones in anesthetized rats by electrophysiological method. We found that an IG injection of LcS suppressed neural activity of sympathetic nerves supplying the white adipose tissue of urethane-anesthetized rats in a dose-dependent manner, whereas sympathetic nerve outflow to brown adipose tissue was not affected by the IG LcS injection. Furthermore, the IG LcS injection reduced efferent sympathetic nerve outflow to the adrenal gland and liver, but did not alter gastric vagal nerve activity, renal sympathetic nerve activity, as well as mean arterial pressure. To test the involvement of afferent vagal nerves and the abdominal organs, we examined the adrenal sympathetic response to an LcS injection in rats with ablated afferent vagal nerves, and found that the adrenal sympathetic nerve response to LcS was inhibited in vagotomized rats. In addition, we found that oral ingestion of LcS attenuated the hyperglycemic response to glucose loading and blood glycerol levels in conscious rats. Our data suggest that LcS might affect tissue-specific autonomic nerves through the afferent vagal nerve pathway to modulate glucose and lipid metabolism.

GPR40 and GPR120 fatty acid sensors are critical for postoral but not oral mediation of fat preferences in the mouse

In addition to orosensory signals, postoral actions of fat stimulate appetite and condition flavor preferences, but the gut sensors mediating these responses are unknown. Here, we investigated the role of the fatty acid sensors GPR40 and GPR120 in postoral and oral preferences for a soybean oil emulsion (Intralipid). Mice were trained to drink a flavored solution (CS+) paired with intragastric (IG) oil infusions and another flavored solution (CS-) paired with water infusions. Knockout (KO) mice missing GPR40 or GPR120 sensors increased their CS+ intake in one-bottle tests (1 h/day) but less so than wild-type (WT) mice. The KO mice also preferred the CS+ to CS- in a two-bottle test, but the preference was attenuated in GPR40 KO mice. Double-knockout (DoKO) mice missing both GPR40 and GPR120 displayed attenuated stimulation of CS+ intake and only a marginal CS+ preference. The DoKO mice developed a more substantial CS+ preference when tested 24 h/day, although weaker than that of WT mice. The DoKO mice also consumed less of the CS+ paired with IG Intralipid, as well as less Intralipid in oral tests. However, DoKO mice, like GPR40 KO and GPR120 KO mice did not differ from WT mice in their preference for Intralipid over water at 0.001%-20% concentrations. In contrast to prior results obtained with mice missing the CD36 fatty acid sensor, these findings indicate that, together, GPR40 and GPR120 play a critical role in the postoral stimulation of appetite by fat but are not essential for oral fat preferences.

Enteral Arginine Partially Ameliorates Parenteral Nutrition–Induced Small Intestinal Atrophy and Stimulates Hepatic Protein Synthesis in Neonatal Piglets

Arginine is an indispensable amino acid in neonates; de novo synthesis of arginine occurs in the small intestine (SI) but is reduced during parenteral nutrition (PN), limiting the arginine available to the mucosa. We assessed the effects of route of intake and dietary concentration of arginine on protein synthesis, superior mesenteric artery (SMA) blood flow, and SI morphology. Piglets (n = 18, 14-17 days old) were given complete PN for 3 days to induce SI atrophy, then switched to 1 of 3 treatments: arginine-free PN plus an intragastric (IG) infusion of high arginine (1.6 g · kg(-1)· d(-1), IG-H Arg) or low arginine (0.6 g · kg(-1)· d(-1), IG-L Arg) or complete high-arginine PN (1.6 g · kg(-1)· d(-1), IV-H Arg). Enteral arginine, irrespective of amount provided, stimulated hepatic protein synthesis compared with intravenous delivery of arginine (P = .01). SMA blood flow declined for all groups following the initiation of PN. After 48 hours on the test diets, all groups reached low constant levels, but the IV-H group was significantly higher than both IG groups (P < .05). Despite greater blood flow, the SI morphological characteristics in IV-H Arg pigs were not significantly improved over the other groups. IV-H Arg pigs had higher plasma concentrations of indispensable amino acids (tyrosine, isoleucine, and valine) compared with IG-H Arg, despite identical amino acid intakes. Intravenous delivery of arginine sustained the best SMA blood flow, whereas even a moderate amount of enteral arginine stimulated liver protein synthesis and maintained SI growth, independent of blood flow.

Post-oral appetite stimulation by sugars and nonmetabolizable sugar analogs

Post-oral sugar actions enhance the intake of and preference for sugar-rich foods, a process referred to as appetition. Here, we investigated the role of intestinal sodium glucose cotransporters (SGLTs) in sugar appetition in C57BL/6J mice using sugars and nonmetabolizable sugar analogs that differ in their affinity for SGLT1 and SGLT3. In experiments 1 and 2, food-restricted mice were trained (1 h/day) to consume a flavored saccharin solution [conditioned stimulus (CS-)] paired with intragastric (IG) self-infusions of water and a different flavored solution (CS+) paired with infusions of 8 or 12% sugars (glucose, fructose, and galactose) or sugar analogs (α-methyl-D-glucopyranoside, MDG; 3-O-methyl-D-glucopyranoside, OMG). Subsequent two-bottle CS+ vs. CS- choice tests were conducted without coinfusions. Infusions of the SGLT1 ligands glucose, galactose, MDG, and OMG stimulated CS+ licking above CS- levels. However, only glucose, MDG, and galactose conditioned significant CS+ preferences, with the SGLT3 ligands (glucose, MDG) producing the strongest preferences. Fructose, which is not a ligand for SGLTs, failed to stimulate CS+ intake or preference. Experiment 3 revealed that IG infusion of MDG+phloridzin (an SGLT1/3 antagonist) blocked MDG appetition, whereas phloridzin had minimal effects on glucose-induced appetition. However, adding phloretin (a GLUT2 antagonist) to the glucose+phloridzin infusion blocked glucose appetition. Taken together, these findings suggest that humoral signals generated by intestinal SGLT1 and SGLT3, and to a lesser degree, GLUT2, mediate post-oral sugar appetition in mice. The MDG results indicate that sugar metabolism is not essential for the post-oral intake-stimulating and preference-conditioning actions of sugars in mice.

Glucose-conditioned flavor preference learning requires co-activation of NMDA and dopamine D1-like receptors within the amygdala

The role of amygdala (AMY) NMDA receptor signaling and its interaction with dopamine D1-like receptor signaling in glucose-mediated flavor preference learning was investigated. In Experiment 1, rats were trained with a flavor (CS+) paired with intragastric (IG) 8% glucose infusions and a different flavor (CS−) paired with IG water infusions. In the two-bottle tests (Expression), bilateral intra-AMY injections of the NMDA receptor antagonist, AP5 (0, 5 and 10nmol/brain), did not block the CS+ preference. In Experiment 2, new rats received intra-AMY injections of either vehicle or AP5 (10nmol), prior to training sessions with CS+/IG glucose and CS−/IG water. In the two-bottle tests without drug treatment, AP5 rats failed to prefer the CS+ flavor (50%). In Experiments 3, new rats were trained as in Experiment 2 except that, during training, half the rats received AP5 injections (5nmol) in one side of the AMY and SCH23390 (D1-like receptor antagonist, 6nmol), in the contralateral AMY (Drug/Drug group). The remaining rats received vehicle injections in one side of the AMY and either AP5 (5nmol) or SCH23390 (6nmol) in the contralateral AMY (Drug/Vehicle group). The two-bottle choice tests without drug treatment revealed that, unlike the Drug/Vehicle group (85%), the Drug/Drug group failed to prefer the CS+ flavor (50%). These results reveal an essential role for AMY NMDA receptor activation in the acquisition of flavor preference learning induced by the post-oral reinforcing properties of glucose and demonstrate that such learning is based on co-activation of NMDA and DA D1 receptors within this forebrain structure.

Central administration of an orexin receptor 1 antagonist prevents the stimulatory effect of Olanzapine on endogenous glucose production

Atypical antipsychotic drugs such as Olanzapine (Olan) induce weight gain and metabolic changes associated with the development of type 2 diabetes. The mechanisms underlying these undesired side-effects are currently unknown. It has been shown that peripheral injections of Olan activate neurons in the lateral hypothalamus/perifornical area and that a large part of these neurons are orexin (Ox) A-positive. We investigated further the possible involvement of the central Ox system in the metabolic side-effects of Olan by comparing the hyperglycaemic effects of an intragastric (IG) Olan infusion between animals treated intracerebroventricularly (ICV) with an Ox-1 receptor antagonist (SB-408124) or vehicle. As observed in previous studies IG Olan caused an increase in blood glucose, endogenous glucose production and plasma glucagon levels. ICV pre-treatment with the Ox-1 receptor antagonist did not affect the Olan-induced hyperglycaemia or increased plasma glucagon concentrations, but the increased endogenous glucose production was blunted by the ICV SB-408124 treatment. From these results we conclude that the metabolic side-effects of Olan are partly mediated by the hypothalamic Ox system.

Diacylglycerol acyltransferase-1 inhibition enhances intestinal fatty acid oxidation and reduces energy intake in rats

Acyl CoA:diacylglycerol acyltransferase-1 (DGAT-1) catalyzes the final step in triacylglycerol (TAG) synthesis and is highly expressed in the small intestine. Because DGAT-1 knockout mice are resistant to diet-induced obesity, we investigated the acute effects of intragastric (IG) infusion of a small molecule diacylglycerol acyltransferase-1 inhibitor (DGAT-1i) on eating, circulating fat metabolites, indirect calorimetry, and hepatic and intestinal expression of key fat catabolism enzymes in male rats adapted to an 8 h feeding-16 h deprivation schedule. Also, the DGAT-1i effect on fatty acid oxidation (FAO) was investigated in enterocyte cell culture models. IG DGAT-1i infusions reduced energy intake compared with vehicle in high-fat diet (HFD)-fed rats, but scarcely in chow-fed rats. IG DGAT-1i also blunted the postprandial increase in serum TAG and increased β-hydroxybutyrate levels only in HFD-fed rats, in which it lowered the respiratory quotient and increased intestinal, but not hepatic, protein levels of Complex III of the mitochondrial respiratory chain and of mitochondrial hydroxymethylglutaryl-CoA synthase. Finally, the DGAT-1i enhanced FAO in CaCo2 (EC50 = 0.3494) and HuTu80 (EC50 = 0.00762) cells. Thus, pharmacological DGAT-1 inhibition leads to an increase in intestinal FAO and ketogenesis when dietary fat is available. This may contribute to the observed eating-inhibitory effect.

Systemic, Renal, and Colonic Effects of Intravenous and Enteral Rehydration in Horses

Intravenous (IV) and intragastric (IG) administration of fluid therapy are commonly used in equine practice, but there are limited data on the systemic, renal, and enteric effects. IV fluid administration will increase intestinal and fecal hydration in a rate-dependent manner after hypertonic dehydration, but will be associated with significant urinary water and electrolyte loss. Equivalent volumes of IG plain water will result in comparatively greater intestinal hydration with less renal loss. Six Thoroughbred geldings. Experimental study. 6 by 6 Latin square design investigating constant rate IV administration at 50, 100, and 150 mL/kg/d over 24 hours in horses dehydrated by water deprivation. Equivalent volumes of IG plain water were administered by 4 bolus doses over 24 hours. Water deprivation resulted in a significant decrease in the percentage of fecal water, and increases in serum and urine osmolality. IV fluids administered at 100 and 150 mL/kg/d restored fecal hydration, but increasing the rate from 100 to 150 mL/kg/d did not confer any additional intestinal benefit, but did result in significantly greater urine production and sodium loss. Equivalent 24-hour volumes of plain water resulted in greater intestinal water and less urine output. IV polyionic isotonic fluids can be used to hydrate intestinal contents in situations where enteral fluids are impractical. IV fluids administered at three times maintenance are no more efficacious and might be associated with adverse physiological findings after withdrawal. Bolus dosing of IG water can be used to restore intestinal water with minimal adverse effects.

Sensory-specific appetition: Postingestive detection of glucose rapidly promotes continued consumption of a recently encountered flavor

It is generally thought that macronutrients stimulate intake when sensed in the mouth (e.g., sweet taste) but as food enters the GI tract its effects become inhibitory, triggering satiation processes leading to meal termination. Here we report experiments extending recent work (see Zukerman et al., 2011 [1]) showing that under some circumstances nutrients sensed in the gut produce a positive feedback effect, immediately promoting continued intake. In one experiment, rats with intragastric (IG) catheters were accustomed to consuming novel flavors in saccharin daily while receiving water infused IG (5ml/15min). The very first time glucose (16% w/w) was infused IG instead of water, intake accelerated within 6min of infusion onset and total intake increased 29% over baseline. Experiment 2 replicated this stimulatory effect with glucose infusion but not fructose nor maltodextrin. Experiment 3 showed that the immediate intake stimulation is specific to the flavor accompanying the glucose infusion. Rats were accustomed to flavored saccharin being removed and replaced with the same or a different flavor. When glucose infusion accompanied the first bottle, intake from the second bottle was stimulated only when it contained the same flavor, not when the flavor switched. Thus we confirm not only that glucose sensed postingestively can have a rapid, positive feedback effect (‘appetition’ as opposed to ‘satiation’) but that it is sensory-specific, promoting continued intake of a recently encountered flavor. This sensory-specific motivation may represent an additional psychobiological influence on meal size, and further, has implications for the mechanisms of learned flavor-nutrient associations.

Post-oral glucose stimulation of intake and conditioned flavor preference in C57BL/6J mice: A concentration–response study

In a recent study, intragastric (IG) self-infusion of 16% glucose stimulated 1-h intake and conditioned a preference for a flavored saccharin solution in C57BL/6J mice (Zukerman et al., 2011). Experiment 1 of the present study presents a concentration–response analysis of IG glucose-induced intake stimulation monitored by recording licking response every min of the 1h/day sessions. Separate groups of food-restricted mice consumed a flavored saccharin solution (the CS−) paired with IG self-infusions of water (Test 0) followed by a different flavored solution (the CS+) paired with IG self-infusions of 2, 4, 8, 16, or 32% glucose (Tests 1–3). Following additional CS− and CS+ training sessions, a two-bottle CS+ vs. CS− choice test was conducted without infusions. Self-infusions of 8%, 16% or 32% glucose stimulated CS+ licking within 12min of the first test session and even earlier in subsequent test sessions, and also conditioned significant CS+ preferences in the two-bottle test. The stimulation of early licking and CS+ preference increased as a function of glucose concentration. The amount of glucose solute self-infused increased with sugar concentration as did post-infusion blood glucose levels. The 2% glucose infusion did not stimulate CS+ intake and the 2% and 4% infusions failed to produce a CS+ preference in the 1-h test. Experiment 2 revealed that intraperitoneal self-infusions of 8% glucose, unlike IG glucose self-infusions, failed to stimulate CS+ licking or preference despite producing maximal increases in blood glucose levels. Taken together, these and other findings suggest that glucose rapidly produces concentration-dependent intestinal signals that stimulate intake and condition flavor preferences while post-oral satiation signals limit total amounts consumed.

Do gastrointestinal taste receptors contribute to associative learning and foraging behavior?1

Foraging behavior is an expression of learning, context, and experience arising from integration of sensory information obtained during feeding with postingestive consequences of food ingestion. Although it has been well established that gustatory and olfactory systems of the mouth and nose provide sensory information to the consumer (in the form of flavor), sweet and bitter taste receptors have recently been identified in the intestinal tract of humans and rodents. It remains possible that sensory information generated in the gut could contribute to the learning process. Thus, a series of experiments was conducted to determine if classical associative learning occurs when the conditional stimulus circumvents oronasal presentation via direct delivery to the gut or peritoneal cavity. Mice receiving an intragastric infusion of 5 mM sodium saccharin immediately followed by LiCl administration demonstrated a significant decrease in preference for 5 mM saccharin in 4 consecutive 23 h, 2-bottle preference tests versus water (P = 0.0053). Saccharin was highly preferred in mice receiving intragastric (IG) saccharin only or interperitoneal (i.p.) injection of LiCl only. This reduced preference indicated that mice "tasted" saccharin infused into the gut. However, efforts to replicate with a reduced infusion volume failed to result in decreased preference. To understand if there were alternative pathways for oral detection of infused saccharin, mice received intragastric infusions (5.4 mM) and i.p. injections (10.8 mM) of sodium fluorescein. Fluorescence was observed from the tongues and esophagi of mice infused with volumes of 0.5 mL or more or injected with volumes of 0.25 mL or greater. Interperitoneal injections of 5 mM saccharin in mice resulted in reduced preference for 5 mM saccharin presented orally in 2-bottle preference tests (P = 0.0287). Oral delivery of a 500-fold less concentration of saccharin (0.01 mM) during conditioning resulted in a similar preference expression as shown in the initial IG experiment. These results demonstrate that although compounds may be tasted in the mouth absent of oral contact, associative learning is attenuated. Therefore, intestinal taste receptors are unlikely to participate directly in learning and recognition of foods during foraging events.

Flavor preferences conditioned by intragastric glucose but not fructose or galactose in C57BL/6J mice

The present study determined if mice, like rats, differ in their flavor conditioning responses to intragastric (IG) infusions of three common monosaccharide sugars. In Experiment 1, C57BL/6J mice were trained to drink a flavored saccharin solution (the CS+) paired with intragastric (IG) self-infusions of 16% glucose, fructose or galactose and a different flavored solution (the CS−) paired with IG water infusions during 22h/day training sessions. The glucose infusions increased CS+ intakes during training and produced a strong CS+ preference (~87%) in two-bottle choice tests. In contrast, the fructose and galactose infusions reduced CS training intakes and did not condition a CS+ preference. Experiment 2 determined if reducing fructose and galactose concentration would enhance conditioning. However, IG infusions of 8% sugar also failed to condition CS+ preferences. The robust conditioning response to IG glucose confirms results obtained with rats, but the indifference of mice to IG fructose and galactose contrasts with preference and avoidance responses observed in rats. The effectiveness of glucose to condition preferences suggests an important role for glucose-specific sensors rather than gut “sweet” taste receptors in the postoral modulation of carbohydrate appetite.

Roles of dopamine D1 and D2 receptors in the acquisition and expression of fat-conditioned flavor preferences in rats

Sugars and fats elicit innate and learned flavor preferences with the latter mediated by flavor–flavor (orosensory) and flavor–nutrient (post-ingestive) processes. Systemic dopamine (DA) D1 (SCH23390: SCH) and D2 (raclopride: RAC), but not opioid antagonists blocked the acquisition and expression of flavor–flavor preferences conditioned by sugars. In addition, systemic D1, but not D2 or opioid antagonists blocked the acquisition of flavor–nutrient preferences conditioned by intragastric (IG) sugar infusions. Given that DA antagonists reduce fat intake, the present study examined whether systemic D1 or D2 antagonists altered the acquisition and/or expression of conditioned flavor preferences (CFP) produced by pairing one novel flavor (CS+, e.g., cherry) with a 3.5% corn oil (CO: fat) solution relative to another flavor (CS−, e.g., grape) paired with a 0.9% CO solution. In an expression study, food-restricted rats were trained to drink either flavored 3.5% or 0.9% CO solutions on alternate days. Subsequent two-bottle tests with the CS+ and CS− flavors mixed in 0.9% CO solutions occurred 0.5h after systemic administration of vehicle (VEH), SCH (50–800nmol/kg) or RAC (50–800nmol/kg). The rats displayed a robust CS+ preference following VEH treatment (87–88%) the expression of which was attenuated by treatment with moderate doses of RAC, and to a lesser degree, SCH. In an acquisition study, six groups of rats received VEH, SCH (25, 50, 200nmol/kg) or RAC (50, 200nmol/kg) 0.5h prior to 1-bottle training trials with CS+ flavored 3.5% and CS− flavored 0.9% (CS−) CO solutions. A seventh Limited VEH group was trained with its training intakes limited to that of the SCH and RAC groups. Subsequent two-bottle tests were conducted with the CS+ and CS− flavors presented in 0.9% CO without injections. Significant and persistent CS+ preferences were observed in VEH (75–82%), Limited VEH (70–88%), SCH25 (75–84%), SCH50 (64–87%), SCH200 (78–91%) and RAC200 (74–91%) groups. In contrast, the group trained with RAC50 displayed a significant initial CS+ preference (76%) which declined over testing to 61%. These data indicate limited DA D1 and D2 receptor signaling involvement in the expression and acquisition of a fat-CFP relative to previous robust effects for sugar-CFP.

Towards a Vaccine for Enterotoxigenic E.coli (ETEC): Comparison of Protection Following Intragastric (IG) or Intranasal (IN) Immunization with an Attenuated O157:H7 E.coli Strain (ZCR533) Expressing ETEC Antigens .

Event Abstract Back to Event Towards a Vaccine for Enterotoxigenic E.coli (ETEC): Comparison of Protection Following Intragastric (IG) or Intranasal (IN) Immunization with an Attenuated O157:H7 E.coli Strain (ZCR533) Expressing ETEC Antigens . Edgar Boedeker1* 1 University of New Mexico, Division of Gastroenterology, United States Byrd W 1 , Boedeker E 1* 1Division of Gastroenterology, University of New Mexico, Albuquerque, NM, USA eboedeker@salud.unm.edu We have previously shown that truncation of intimin in a rabbit enteropathogenic E.coli (REPEC) strain yields an attenuated strain which is immunogenic and protective against homologous REPEC challenge1. We have developed a similar intimin mutant (designated ZCR533) in an O157:H7 shiga toxin producing E.coli (STEC) strain to serve not only as an STEC vaccine, but also for use as a vector to express antigens of other pathogens. To develop a safe, live attenuated vaccine against enterotoxigenic E.coli (ETEC) we expressed two critical ETEC antigens, CFA/I and detoxified LT, in ZCR533 and then tested the resulting strains for immunogenicity and protective efficacy in a streptomycin-treated treated mouse model of intestinal ETEC infection. BALB/c mice were vaccinated by the IG or IN routes, then challenged with ETEC H10407 or purified LT. IG delivery of three doses, or IN delivery of two doses, of the vaccine strain to BALB/C mice induced serum IgG and mucosal IgA antibodies to CFA/I and LT. Both IG and IN administration of the ETEC vaccine significantly reduced intestinal bacterial colonization after an oral challenge with ETEC (vac. vs. sham, P<0.05). However, decreased intestinal fluid accumulation following oral challenge with ETEC, or with purified LT, was seen only in the IG vaccinated mice (vac. vs. sham, P<0.05), but not in those vaccinated IN. These studies suggest that both IG and IN administered vaccine led to protective serum and mucosal responses against colonization, but IG vaccination may better protect against toxin-induced fluid accumulation. Reference: 1. Agin et al. Infect. Immun. 73:6608-19, 2005 Keywords: attenuated vaccine against ETEC, intimin mutant Conference: ECMIS - E. coli and the Mucosal Immune System : Interaction, Modulation and Vaccination, Ghent, Belgium, 2 Jul - 5 Jul, 2011. Presentation Type: Oral Presentation Topic: Abstracts Citation: Boedeker E (2012). Towards a Vaccine for Enterotoxigenic E.coli (ETEC): Comparison of Protection Following Intragastric (IG) or Intranasal (IN) Immunization with an Attenuated O157:H7 E.coli Strain (ZCR533) Expressing ETEC Antigens .. Front. Immunol. Conference Abstract: ECMIS - E. coli and the Mucosal Immune System : Interaction, Modulation and Vaccination. doi: 10.3389/conf.fimmu.2012.01.00006 Copyright: The abstracts in this collection have not been subject to any Frontiers peer review or checks, and are not endorsed by Frontiers. They are made available through the Frontiers publishing platform as a service to conference organizers and presenters. The copyright in the individual abstracts is owned by the author of each abstract or his/her employer unless otherwise stated. Each abstract, as well as the collection of abstracts, are published under a Creative Commons CC-BY 4.0 (attribution) licence (https://creativecommons.org/licenses/by/4.0/) and may thus be reproduced, translated, adapted and be the subject of derivative works provided the authors and Frontiers are attributed. For Frontiers’ terms and conditions please see https://www.frontiersin.org/legal/terms-and-conditions. Received: 13 Oct 2011; Published Online: 09 Jan 2012. * Correspondence: Prof. Edgar Boedeker, University of New Mexico, Division of Gastroenterology, Albuquerque, New Mexico, 87031, United States, eboedeker@salud.unm.edu Login Required This action requires you to be registered with Frontiers and logged in. To register or login click here. Abstract Info Abstract The Authors in Frontiers Edgar Boedeker Google Edgar Boedeker Google Scholar Edgar Boedeker PubMed Edgar Boedeker Related Article in Frontiers Google Scholar PubMed Abstract Close Back to top Javascript is disabled. Please enable Javascript in your browser settings in order to see all the content on this page.

Intra-amygdala inhibition of ERK1/2 potentiates the discriminative stimulus effects of alcohol

Extracellular signal-regulated kinase (ERK1/2) has been implicated in modulating drug seeking behavior and is a target of alcohol and other drugs of abuse. Given that the discriminative stimulus (subjective/interoceptive) effects of drugs are determinants of abuse liability and can influence drug seeking behavior, we examined the role of ERK1/2 in modulating the discriminative stimulus effects of alcohol. Using drug discrimination procedures, rats were trained to discriminate a moderate intragastric (IG) alcohol dose (1g/kg) versus water (IG). Following an alcohol (1g/kg) discrimination session phosphorylated ERK1/2 (pERK1/2) immunoreactivity (IR) was significantly elevated in the amygdala, but not the nucleus accumbens. Therefore, we hypothesized that intra-amygdala inhibition of ERK1/2 would disrupt expression of the discriminative stimulus effects of alcohol. However, intra-amygdala or accumbens administration of the MEK/ERK1/2 inhibitor U0126 (1 and 3μg) had no effect on the discriminative stimulus effects of the training dose of alcohol (1g/kg). Contrary to our hypothesis, intra-amygdala infusion of U0126 (3μg) potentiated the discriminative stimulus effects of a low alcohol dose (0.5g/kg) and had no effect following nucleus accumbens infusion. Importantly, site-specific inhibition of pERK1/2 in each brain region was confirmed. Therefore, the increase in pERK1/2 IR in the amygdala following systemic alcohol administration may be reflective of the widespread effects of alcohol on the brain (activation/inhibition of brain circuits), whereas the site specific microinjection studies confirmed functional involvement of intra-amygdala ERK1/2. These findings show that activity of the ERK signaling pathway in the amygdala can influence the discriminative stimulus effects of alcohol.

Rapid post-oral stimulation of intake and flavor conditioning by glucose and fat in the mouse

Although widely assumed to have only satiating actions, nutrients in the gut can also condition increases in intake in some cases. Here we studied the time course of post-oral nutrient stimulation of ingestion in food-restricted C57BL/6J mice. In experiment 1, mice adapted to drink a 0.8% sucralose solution 1 h/day, rapidly increased their rate of licking (within 4-6 min) when first tested with an 8% glucose solution and even more so in tests 2 and 3. Other mice decreased their licking rate when switched from sucralose to 8% fructose, a sugar that is sweet like glucose but lacks positive post-oral effects in mice. The glucose-stimulated drinking is due to the sugar's post-oral rather than taste properties, because sucralose is highly preferred to glucose and fructose in brief choice tests. A second experiment showed that the glucose-stimulated ingestion is associated with a conditioned flavor preference in both intact and capsaicin-treated mice. This indicates that the post-oral stimulatory action of glucose is not mediated by capsaicin-sensitive visceral afferents. In experiment 3, mice consumed flavored saccharin solutions as they self-infused water or glucose via an intragastric (IG) catheter. The glucose self-infusion stimulated ingestion within 13-15 min in test 1 and produced a conditioned increase in licking that was apparent in the initial minute of tests 2 and 3. Experiment 4 revealed that IG self-infusions of a fat emulsion also resulted in post-oral stimulation of licking in test 1 and conditioned increases in tests 2 and 3. These findings indicate that glucose and fat can generate stimulatory post-oral signals early in a feeding session that increase ongoing ingestion and condition increases in flavor acceptance and preference revealed in subsequent feeding sessions. The test procedures developed here can be used to investigate the peripheral and central processes involved in stimulation of intake by post-oral nutrients.

Towards a Vaccine for Enterotoxigenic E. coli (ETEC): Comparison of Protection Following Intragastric (IG) or Intranasal (IN) Immunization with an Attenuated O157:H7 E. coli Strain (ZCR533) Expressing ETEC Antigens

Purpose: Enterotoxigenic E. coli (ETEC) strains are a principal cause of diarrhea in travelers from industrialized nations to developing countries, and they are a frequent cause of infantile diarrhea in the developing world. Although the virulence mechansims of ETEC diarrhea are well understood and vaccine targets are well defined, there are currently no approved vaccines to prevent ETEC diarrhea in adults or infants. Our long term goal is to develop a live, attenuated oral vaccine for ETEC infections. Methods: To deliver ETEC antigens, we have developed an attenuated E. coli strain to serve as a live vector for orogastric administration. We have previously shown that truncation of the adhesin intimin in a rabbit enteropathogenic E. coli (REPEC) strain yields an attenuated strain which is immunogenic and protective against homologous REPEC challenge(1). We have developed a similar intimin mutant (designated ZCR533) in an O157:H7 shiga toxin producing E. coli (STEC) strain to serve not only as an STEC vaccine, but also for use as a vector to express antigens of other pathogens such as ETEC. To develop a safe, live attenuated vaccine against enterotoxigenic E. coli (ETEC), we expressed two critical ETEC antigens, colonization factor antigen I (CFA/I) and detoxified heart labile enterotoxin (LT), in ZCR533 and then tested the resulting strains for immunogenicity and protective efficacy in a streptomycin-treated treated mouse model of intestinal ETEC infection. BALB/c mice were vaccinated by the IG or IN routes, then challenged with ETEC H10407 or purified LT. Results: IG delivery of three doses, or IN delivery of two doses, of the vaccine strain to BALB/C mice induced serum IgG and mucosal IgA antibodies to CFA/I and LT. Both IG and IN administration of the ETEC vaccine significantly reduced intestinal bacterial colonization after an oral challenge with ETEC (vac. vs. sham, P<0.05). However, decreased intestinal fluid accumulation following oral challenge with ETEC, or with purified LT, was seen only in the IG vaccinated mice (vac. vs. sham, P<0.05), but not in those vaccinated IN. Conclusion: These studies suggest that both IG and IN administered vaccine led to protective serum and mucosal responses against colonization, but IG vaccination may better protect against toxin-induced fluid accumulation.

Intragastric infusion of pea-protein hydrolysate reduces test-meal size in rats more than pea protein

Because protein hydrolysates are digested faster than the corresponding proteins, they may increase or hasten the acute eating-inhibitory effect of protein. Potential mediating mechanisms include accelerated or greater release of satiating gut peptides and activation of metabolic signals that inhibit eating. We tested these hypotheses in adult male rats that were surgically equipped with intragastric (IG) cannulas and adapted to 30-min test meals at dark onset after 14-h food deprivation. Equiosmotic 12ml loads of saline–urea control (C), 13.6% pea protein (PP), or 13.6% PP hydrolysate (PPH, DSM/DFS, Delft, The Netherlands) solutions were IG infused in 1min just before test meals. PPH reduced test-meal size compared to C more than PP (−3.8±0.3g vs. −2.6±0.4g; P<0.0001). Plasma glutamate increased more after PPH than PP (P<0.0001). Plasma lactate, alanine, insulin, glucagon, GLP-1 and paracetemol (an index of gastric emptying) all increased similarly, and glucose decreased similarly, after PPH or PP. Finally, PPH still reduced test-meal size more than PP (−4.6±0.3g vs. −3.1±0.4g; P<0.001) in rats after subdiaphragmatic vagal deafferentation, indicating that abdominal vagal afferents are not necessary for the eating-inhibitory effects of PP and PPH and, by extension, that gut peptides whose satiating effects depend on intact vagal afferents (e.g., CCK and glucagon) do not play crucial roles. Thus, PPH reduced short-term food intake more than PP under our conditions, but the mechanism(s) involved remain unclear.