Saccharin Solution Research Articles

The importance of fit testing in decontamination of N95 respirators: A cautionary note

To the Editor: The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) COVID-19 pandemic resulted in a critical shortage of personal protective equipment (PPE), particularly N95 filtering facepiece respirators (FFRs). Decontamination methods and reuse of FFRs, including ultraviolet germicidal irradiation (UVGI), hydrogen peroxide vaporization, microwave-generated steaming, and dry heating, have been rushed into implementation. However, if the treatment affects filtration or fit, decontamination is achieved but loss of integrity could be catastrophic to the wearer. Our recent JAAD publication discusses research with a repurposed dermatology phototherapy desktop device to administer UVGI for N95 decontamination.1Hamzavi I. Lyons A.B. Kohli I. et al.Ultraviolet germicidal irradiation: possible method for respirator disinfection to facilitate reuse during COVID-19 pandemic.J Am Acad Dermatol. 2020; 82: 1511-1512Abstract Full Text Full Text PDF PubMed Scopus (90) Google Scholar This letter highlights critical differences in fit testing performance collected for different respirator models treated with UVGI administered with this repurposed unit. The effects on respirators of using the suggested UVGI dose of 1 to 2 J/cm2 were variable.2Heimbuch B.K. Harnish D. Research to Mitigate a Shortage of Respiratory Protection Devices During Public Health Emergencies.2020https://www.ara.com/sites/default/files/MitigateShortageofRespiratoryProtectionDevices_3.pdfDate accessed: April 10, 2020Google Scholar The respirator fit testing was conducted by the Henry Ford Health System Department of Infection Prevention and Control according to the saccharin solution aerosol protocol laid out by the United States Occupational Safety and Health Administration (OSHA).3Occupational Safety and Health AdministrationAppendix A to §1910.134—Fit Testing Procedures (Mandatory).https://www.osha.gov/laws-regs/regulations/standardnumber/1910/1910.134AppADate accessed: April 10, 2020Google Scholar Irradiation of respirators with UVGI was conducted by the Henry Ford Health System Department of Dermatology Photomedicine Unit. A new, unused respirator served as the test respirator, and irradiation was performed after establishing that an unused respirator passed a baseline fit test. The outside-facing and wearer-facing surfaces of the respirators were irradiated by the Daavlin Desktop UVC Germicidal Lamp (Daavlin, Bryan, OH) with a dose of 1.5 J/cm2 to each side. If the respirator passed this test, it was considered to have successfully completed 1 cycle. This process was then repeated to establish the number of irradiation cycles that the respirator would pass the fit test. Testing was ceased if a respirator did not pass the fit test. The results are reported in Table I.Table IResults of Henry Ford Health System respirator fit testingFFR model∗3M, St Paul, Minnesota; Cardinal Health, Dublin, Ohio; Moldex-Metric, Culver City, California.Saccharin solution aerosol fit test performedUVC cycles attempted/fit test cycles passedPassing cumulative UVC dose (3 J/cm2 = 1 cycle)3M N95 Respirator—1860 NIOSH TC-84A-0006Baseline, cycles 1-6, 15, 20 & 2525/2060 J/cm23M N95 Respirator—9210 NIOSH TC-84A-2669Baseline, cycles 1-22/2†Limited resources prevented testing of additional UVC cycles.6 J/cm23M N95 Respirator—8210 NIOSH TC-84A-0007Baseline, cycles 1-22/13 J/cm2Cardinal Health USA N95 R/S Respirator—NIOSH TC-84A-5529 & 5527 (small/regular)Baseline, cycles 1-22/13 J/cm2Moldex N95 Respirator #2300N95—NIOSH TC-84A-0328This N95 respirator passed the baseline fit test on 1 individual. Owing to immediate breakage of straps upon user removal on 2 respirators, testing ceased.0N/AMoldex N95 Respirator 1511 (small)—NIOSH TC-84A-0013This N95 respirator failed the baseline fit test on 3 individuals.0N/AMoldex N95 Respirator 1512 (medium)—NIOSH TC-84A-0013Baseline, cycles 1-33/26 J/cm23M N95 Respirator—9010 NIOSH TC-84A-4243This N95 respirator failed the baseline fit test on 2 individuals.0N/ACardinal Health USA N95A-S Respirator—NIOSH TC-84A-5463This N95 respirator failed the baseline fit test on 2 individuals.0N/AGB2626-2206 KN95 Respirator—KN95-01-01This N95 respirator failed the baseline fit test on 2 individuals.0N/AFFR, Filtering facepiece respirator; N/A, not available; NIOSH, National Institute for Occupational Safety and Health; UVC, ultraviolet C.∗ 3M, St Paul, Minnesota; Cardinal Health, Dublin, Ohio; Moldex-Metric, Culver City, California.† Limited resources prevented testing of additional UVC cycles. Open table in a new tab FFR, Filtering facepiece respirator; N/A, not available; NIOSH, National Institute for Occupational Safety and Health; UVC, ultraviolet C. The UVGI treatment may degrade polymers in the respirators themselves and impact the elasticity of the bands.4Lindsley W.G. Martin Jr., S.B. Thewlis R.E. et al.Effects of ultraviolet germicidal irradiation (UVGI) on N95 respirator filtration performance and structural integrity.J Occup Environ Hyg. 2015; 12: 509-517Crossref PubMed Scopus (164) Google Scholar The myriad respirators available in this crisis react differently to a given UVGI dose and survive different numbers of decontamination cycles. This may hold true for other respirator treatment methods as well. Our data strongly indicate that to protect the safety of the N95 respirator user, fit testing after decontamination must be done each time a new model is introduced to a health care system. This has significant safety implications, because varied decontamination methods are being used by different institutions.5Torres A, Lyons AB, Narla S et al. Ultraviolet-C and other methods of decontamination of filtering facepiece N-95 respirators during the COVID-19 pandemic [e-pub ahead of print]. Photochem Photobiol Sci. https://doi.org/10.1039/D0PP00131G. Accessed April 10, 2020.Google Scholar In addition, N95 respirators should be physically examined before and after decontamination cycles to check for signs of degradation that may have occurred while removing and handling.

Fetal Alcohol Exposure Alters Mammary Epithelial Cell Subpopulations and Promotes Tumorigenesis.

Fetal alcohol exposure (FAE) increases the risk of mammary tumorigenesis in adult offspring; however, the underlying mechanism remains unknown. This study tested the hypothesis that FAE shifts the mammary epithelial cell (MEC) composition toward one that promotes tumorigenesis. Pregnant Friend Virus BNIH Jacksondams bred to MMTV-Wnt1 male mice were given ad libitum access to 5% alcohol in 0.2% saccharin solution from GD9-10 and 10% alcohol in 0.2% saccharin from GD11-GD19 or 0.2% saccharin solution from GD9-GD19. Thoracic and inguinal mammary glands from wild-type (WT) and transgenic (Tg) female offspring were harvested at 5 and 10weeks of age and dissociated to yield a single cell suspension enriched for MECs for flow cytometry, mammosphere assay, and gene analysis. A subset of Tg offspring was followed for tumor formation. WT glands of FAE animals exhibited a decreased basal cell population and increased luminal: basal ratio at 10weeks of age. qRT-PCR analysis of total MECs found that Hey1 mRNA expression was increased in the WT FAE group at 10weeks of age. In Tg glands, FAE increased the luminal progenitor cell population at 5weeks of age but did not alter MEC composition at 10weeks of age. Tertiary mammosphere-forming efficiency was greater in the WT glands of FAE animals at 10weeks of age. Tumor latency was decreased in the FAE group. Flow cytometry analysis indicated that FAE females developed tumors with an increased basal cell population. These data indicate that FAE can shift MEC subpopulations, increasing the proportion of cells that are potentially vulnerable to transformation and affecting cancer risk.

Examination of nicotine and saccharin reward in the Goto-Kakizaki diabetic rat model

Morbidity and mortality attributed to type 2 diabetes have exponentially increased in the US. At exceptionally high risk is a subpopulation of persons with type 2 diabetes who smoke, which are shown to have decreased success rates of smoking cessation than euglycemic smokers. Preclinical research in our laboratory has shown that the rewarding effects of nicotine are enhanced in the streptozotocin and high-fat diet rodent model of diabetes. It is presently unclear whether this enhancement of nicotine reward can be demonstrated in other insulin resistant rat models. This study aimed to determine if a similar increase in nicotine reward is found in Goto-Kakizaki (GK) rats, a model of the spontaneous formation of insulin resistance in an inbred sub-strain of Wistar rat. Nicotine conditioned place preference (CPP) was examined in Sprague-Dawley (SD), Wistar, and GK rats. A robust nicotine CPP was found in SD and Wistar rats, but nicotine CPP was not detected in GK rats. Locomotor activity was also evaluated in all three strains, and GK rats demonstrated significantly less activity as compared to SD and Wistar rats. To further assess reward behavior in GK rats, consumption of saccharin solution was measured over a 48 -h period. GK rats showed a significant increase in saccharin intake compared to SD rats. These findings suggest that GK rats experience an enhanced hedonic processing as compared to SD rats. The lack of nicotine CPP in GK rats may be due to deficits in learning and memory, thus hindering their ability to acquire or express a place preference.

Reduced acceptance of saccharin solutions by rats previously consuming more highly palatable solutions.

Rats first given 24-h access to 10% sucrose for 4 or 12 days (Stage 1) were then switched to a saccharin solution for a 12-day Stage 2. The initial result of this switch was that these Sucrose groups drank less saccharin than Water groups that had been given only water to drink in Stage 1. This difference was maintained throughout Stage 2 by the females that served in Experiments 1 and 4 and by the males that served in Experiment 3. Experiment 1 also found that access to 10% glucose in Stage 1 produced an essentially identical decrease in subsequent saccharin acceptance as that produced by giving 10% sucrose in Stage 1. The impact on subsequent acceptance of saccharin was also tested in rats given two types of maltodextrin solution. The first type of maltodextrin (Myopure brand) was used with the males in Experiment 2; this failed to find any difference between the Maltodextrin and the Water group. However, when a second type of maltodextrin (SolCarb brand) was given to males in Stage 1 of Experiment 3, the results for this group were similar to those from a group given sucrose in Stage 1. The final experiment confirmed that prior exposure to maltodextrin solutions can reduce saccharin acceptance by female rats. Overall, the results suggest that acceptance of saccharin is sensitive to a contrast effect, in that it is reduced by prior exposure to a solution that is more palatable but not necessarily sweet.

Manipulations of Central Amygdala Neurotensin Neurons Alter the Consumption of Ethanol and Sweet Fluids in Mice.

The central nucleus of the amygdala plays a significant role in alcohol use and other affective disorders; however, the genetically-defined neuronal subtypes and projections that govern these behaviors are not well known. Here we show that neurotensin neurons in the central nucleus of the amygdala of male mice are activated by in vivo ethanol consumption and that genetic ablation of these neurons decreases ethanol consumption and preference in non-ethanol-dependent animals. This ablation did not impact preference for sucrose, saccharin, or quinine. We found that the most robust projection of the central amygdala neurotensin neurons was to the parabrachial nucleus, a brain region known to be important in feeding behaviors, conditioned taste aversion, and alarm. Optogenetic stimulation of projections from these neurons to the parabrachial nucleus is reinforcing, and increases ethanol drinking as well as consumption of sucrose and saccharin solutions. These data suggest that this central amygdala to parabrachial nucleus projection influences the expression of reward-related phenotypes and is a novel circuit promoting consumption of ethanol and palatable fluids.SIGNIFICANCE STATEMENT Alcohol use disorder (AUD) is a major health burden worldwide. Although ethanol consumption is required for the development of AUD, much remains unknown regarding the underlying neural circuits that govern initial ethanol intake. Here we show that ablation of a population of neurotensin-expressing neurons in the central amygdala decreases intake of and preference for ethanol in non-dependent animals, whereas the projection of these neurons to the parabrachial nucleus promotes consumption of ethanol as well as other palatable fluids.

Low-calorie sweeteners cause only limited metabolic effects in mice.

There are widespread concerns that low-calorie sweeteners (LCSs) cause metabolic derangement. These concerns stem in part from prior studies linking LCS consumption to impaired glucose tolerance in humans and rodents. Here, we examined this linkage in mice. In experiment 1, we provided mice with chow, water, and an LCS-sweetened solution (saccharin, sucralose, or acesulfame K) for 28 days and measured glucose tolerance and body weight across the exposure period. Exposure to the LCS solutions did not impair glucose tolerance or alter weight gain. In experiment 2, we provided mice with chow, water, and a solution containing saccharin, glucose, or a mixture of both for 28 days, and tested for metabolic changes. Exposure to the saccharin solution increased the insulinemic response of mice to the glucose challenge, and exposure to the saccharin + glucose solution increased the rate of glucose uptake during the glucose challenge. However, neither of these test solutions altered glucose tolerance, insulin sensitivity, plasma triglycerides, or percent body fat. In contrast, exposure to the glucose solution increased glucose tolerance, early insulin response, insulin sensitivity, and percent body fat. We conclude that whereas the LCS-containing solutions induced a few metabolic changes, they were modest compared with those induced by the glucose solution.

Conditioned taste avoidance induced by the combination of heroin and cocaine: Implications for the use of speedball

Speedball (heroin + cocaine) is a prevalent drug combination among intravenous drug users. Although its use is generally discussed to be a function of changes in the rewarding effects of either or both drugs, changes in the aversive effects of either drug may also be impacted (weakened) by the combination. To address this latter possibility and its potential role in the use of speedball, the present studies examined the interaction of cocaine and heroin in taste avoidance conditioning. In Experiment 1, male Sprague-Dawley rats were given access to a novel saccharin solution and then injected with either vehicle or heroin (3.2 mg/kg, IP) followed immediately by various doses of cocaine (10, 18 or 32 mg/kg, SC). At the two lowest doses of cocaine, only animals injected with the drug combination (H + C) displayed a taste avoidance relative to control subjects (taste avoidance was induced with both the combination and the high dose of cocaine). At no dose did animals injected with the combination of heroin and cocaine drink more than animals injected with cocaine alone. In Experiment 2, male Sprague-Dawley rats were similarly treated but injected with vehicle or cocaine (10 mg/kg) followed by injections of various doses of heroin (1.8, 3.2, 5.6 or 10 mg/kg). At the three highest doses of heroin, only animals injected with the drug combination (C + H) displayed significant avoidance relative to control subjects (no avoidance was evident with the combination of cocaine and the low dose of heroin). At no dose did animals injected with the combination of cocaine and heroin drink more than animals injected with heroin alone. Together, these results suggest that the aversive effects of heroin and cocaine are not attenuated by co-administration by cocaine and heroin, respectively. The importance of this for the use of speedball was discussed.

Capsaicin-induced visceral deafferentation does not attenuate flavor conditioning by intragastric fat infusions in mice

The postoral actions of sugar and fat can rapidly stimulate the intake of and preference for flavors associated with these nutrients via a process known as appetition. Prior findings revealed that postoral glucose appetition is not attenuated following capsaicin-induced visceral deafferentation. The present experiment determined if capsaicin treatment altered fat appetition in C57BL/6 mice. Following capsaicin (Cap) or control (Con) treatment, mice were fitted with chronic intragastric (IG) catheters. They were then given 1-h sessions with a flavored saccharin solution (CS-) paired with IG water infusion or a different flavor (CS+) paired with IG 6.4% fat infusion. IG fat stimulated CS+ intakes in both Cap and Con mice, and the groups displayed similar preferences for CS+ over CS- in two-choice tests. These results confirm prior reports of normal fat conditioning in rats exposed to capsaicin or vagal deafferentation surgery. In contrast, other recent findings indicate that total or selective vagotomy alters the preference of mice for dilute vs. concentrated fat sources.

Inactivation of the basolateral amygdala suppresses the expression of taste neophobia but not the retrieval process in attenuation of neophobia

Taste neophobia is a behavior seen in rodents that involves reduction in the consumption of a novel food or drink. In the absence of negative post-ingestive consequences, consumption increases with exposure. In this study, we examined the effect of pharmacological inactivation of the basolateral nucleus of the amygdala (BLA) on taste neophobia in rats using muscimol, a GABAA receptor agonist. Rats treated with muscimol infused into the bilateral BLA showed a suppressed but not totally abolished neophobic reaction to a novel saccharin solution compared to that observed in control rats. This result indicates that BLA function is important, but not essential, for expression of a neophobic reaction to a novel sweet taste solution. However, infusion of muscimol into the BLA did not disrupt attenuation of neophobia, which implies the presence of a retrieval process in safe taste memory.

Bingeing in rats: Persistence of high intakes of palatable solutions induced by 1-day-in-4 intermittent access

When animals are given access to a palatable food or drink on some days but not on others, the amount they consume can far exceed the daily amounts consumed by controls given daily access. A previous study demonstrated such bingeing when rats were given 4% sucrose solution. Importantly, it also found that, following 1-day-in-4 access for many weeks, intakes remained persistently higher than that of controls even when the conditions were changed to 1-day-in-2 access for both groups. One aim of the three experiments reported here was to test whether such persistent bingeing could be found for other solutions. This was confirmed in rats for a saccharin solution and a highly palatable saccharin-plus-glucose solution. When a maltodextrin solution was used, the 1-day-in-4 schedule initially produced higher intakes than controls given daily access. However, the difference between these groups was not maintained when both were switched to a 1-day-in-2 schedule. These results suggest that the hedonic value of a solution is more important than its caloric content in determining whether it will support persistent bingeing. A second aim was to test for evidence that the 1-day-in-4 procedure induced an addiction to the target solution. No such evidence was found using multiple measures including instrumental responding and anxiety-like behavior on the elevated plus-maze for craving and withdrawal respectively.

Combined effect of glyphosate, saccharin and sodium benzoate on the gut microbiota of rats

Glyphosate is the main component of many broadly used herbicides due to its safety for humans and animals. It is known that the remains of glyphosate are present in allowable doses in fodders and food products, and, consumrd in low doses, it is found in insignificant amounts in milk, eggs and even in the internal organs (liver, kidneys) of animals. For determining combined impact of glyphosate and the commonest food additives on the composition of microbiota of animals, four groups of laboratory male rats were formed, which during 42 days consumed pure water without any restrictions; 1% aqueous solution of glyphosate; 1% solution of glyphosate in combination with 1% solution of sodium benzoate; 1% solution of glyphosate with 1% solution of saccharin. After killing the animals, 1 g of feces were collected and by serial dilutions with 10–1 to 10–9 sterile physiologic solution, a microbiological analysis was undertaken. Out of each dilution an inoculation of the studied material to the elective growth media was performed, by 0.1 cm3, then the material was incubated in a thermostat (24–72 hours, temperature 37 °С), the results were recorded after 24–72 h. The microorganisms were identified by studying morphological parameters, tinctorial, cultural and enzymic properties. Results are provided in CFU/g (colony-forming unit per gramm) of feces. The impact of glyphosate and glyphosate with food additives led to no changes in the number of Escherichia coli and emergence of this species of microorganism with changed enzymic activity. Also no changes occurred in the number of microorganisms of Bifidobactrium and Lactobacillus spp. Addition of glyphosate, and also glyphosate in combination with saccharin to the diet contributes to broader reproduction of microorganisms of Klebsiella, Citrobacter, Enterobacter and Pseudomonas genera. Mixtures of glyphosate and food additives allow conditionally pathogenic yeast-like Candida fungi (Candida glabrata and C. albicans) to spread more widely in the intestine. Significant fluctuations in the number of Enterococcus spp. bacteria genus were observed: by 80 times within range of each of the three experimental groups of rats with addition of herbicide with benzoate and saccharin to the diet.

Feasibility of replacing homemade solutions by commercial products for qualitative fit testing of particulate respirators: a mixed effect logistic regression study

Qualitative fit testing is mandatory for tight-fitting respirators to ensure that the wearer fitted properly before entering a contaminated workplace. The purpose of this study was to evaluate the homemade solutions as substitution of commercial products for qualitative fit testing of particulate respirators. Two homemade solutions of Bitrex™ and saccharin were made according to the Occupational Safety and Health Administration (OSHA) regulation 29 CFR 1910.134. Threshold Screening Tests (TSTs) of commercial solutions, as well as homemade ones, were conducted on 62 participants in a random order. A placebo was also tested to assure the participants could distinguish its flavorless from other taste of solutions. There were no statistically significant differences between the commercial and homemade solutions representing that participants detected the bitter taste of the Bitrex™ and sweet taste of the saccharin solutions (96.8% vs. 91.9% and 93.5% vs. 83.9%, respectively). Homemade solutions that were stable and haven’t been contained microbial contaminations, could be substituted for commercial products in qualitative fit testing of filtering face-piece respirators (FFRs). Overall, this protocol presents a practical and cost-benefit technique to assess the fit testing of FFRs.

Acquisition and expression of sucrose conditioned flavor preferences following dopamine D1, opioid and NMDA receptor antagonism in C57BL/6 mice

The study of inbred mouse strains is a useful animal model to assess differences in ingestive behavior responses, including conditioned flavor preferences (CFP). C57BL/6, BALB/c and SWR inbred mice display differential sensitivity to dopamine (DA) D1, opioid and muscarinic cholinergic receptor antagonism of sucrose or saccharin intake as well as to muscarinic cholinergic antagonism of acquisition (learning) of sucrose-CFP. Given that DA D1, opioid and N-methyl-D-aspartate (NMDA) receptor antagonists differentially alter sucrose-CFP in BALB/c and SWR inbred mice, the present study examined whether systemic administration of naltrexone, SCH23390 or MK-801 altered acquisition and expression of sucrose-CFP in C57BL/6 mice. In acquisition experiments, male food-restricted C57BL/6 mice were treated with vehicle, naltrexone (1, 5 mg/kg), SCH23390 (50, 200 nmol/kg) or MK-801 (100, 200 µg/kg) 30 min prior to each of ten daily sessions in which they alternately consumed a flavored (CS+, e.g. cherry) 16% sucrose solution and a differently-flavored (CS-, e.g. grape) 0.05% saccharin solution followed by six two-bottle CS choice tests mixed in 0.2% saccharin without injections. SCH23390 and MK-801, but not naltrexone eliminated sucrose-CFP acquisition in food-restricted C57BL/6 mice. In expression experiments, food-restricted C57BL/6 mice underwent the ten training sessions without injections followed by two-bottle CS choice tests 30 min following vehicle, naltrexone (1, 5 mg/kg), SCH23390 (200, 800 nmol/kg) or MK-801 (100, 200 µg/kg). SCH23390 more effectively reduced the magnitude of sucrose-CFP expression than naltrexone or MK-801 in food-restricted C57BL/6 mice. Thus, dopamine D1 and NMDA receptor signaling is essential for learning of sucrose-CFP in C57BL/6 mice.

Combined effect of glyphosphate, saccharin and sodium benzoate on rats

Herbicides and food additives are included in many food products for humans. Non-used products or products beyond their expiry date are deposited in places of utilizatioin of solid municipal wastes, where they can take effects on the organisms of mouse-like rodents. Among the herbicides, glyphosphate takes first place in the world for volume of production, and is the most intensely used in agricultural farming. The discussion about negative impact on the organisms of mammals, especially against the background of using various substances and environmental factors, continues. In this study, we determined the combined effect of glyphosphate and food additives on the organism of laboratory animals, which manifested in changes in body weight, condition and indices of mass of the internal organs and blood parameters. Four groups of laboratory male rats were formed, which over 42 days received: unlimited access to clean water; 1% aqueous solution of glyphosate; 1% solution of glyphosphate and 1% solution sodium benzoate; 1% solution of glyphosphate with 1% solution of saccharin. Glyphosphate and glyphosphate with sodium benzoate and saccharin significantly reduced the daily increases in body weight of animals compared to the control group. The studied substances have notable suppressive effect on the immune system and haematopoiesis in general, which is manifested in reduce of relative mass of the thymus and spleen against the background of increase in the amount of lymphocytes in the peripheral blood. The inhibition of haematopoiesis is indicated by decrease in the amount of erythrocytes, neurophils and hemoglobin of blood of animals from the experimental groups. The impact on the digestive system of glyphosphate and food additives is indicated by occurance of the effect of “irritation” of mucous membranes, and, as a result, disorders in absorption followed by the disorder in metabolic processes. A dysbalance occurs in enzymic systems of the organism, which is manifested in distrophic processes, especially in the liver parenchyma, indicated by the activity of blood enzymes (ALT, AST, alkaline phosphatase), total number and ratio of proteins of blood plasma. We determined the impact of glyphosphate and its mixes with benzoate and saccharin on the pancreas, which manifests in severe pancreatitis with steep increase in the level of glucose of blood. The results of the study allow us to state that mixture of glyphosphate and food additives can cause toxic effect in animals and humans, which often contact with herbicides.

Identification of central mechanisms underlying anorexigenic effects of intraperitoneal L-tryptophan.

A free essential amino acid, L-tryptophan (TRP), administered through a diet or directly into the gut, decreases food intake by engaging neural mechanisms. The ability of intragastric TRP to cross into the general circulation and through the blood-brain barrier, at least partly underlies hypophagia. It is unclear although, whether TRP's anorexigenic effects and accompanying neural processes occur in the absence of the initial action of TRP on the gut mucosa. Here, we addressed this issue by using a fundamental approach of examining effects of intraperitoneally administered TRP on feeding and neuronal activation in rats. We found that 30 mg/kg, intraperitoneal, TRP decreases deprivation-induced intake of standard chow and thirst-driven water intake. A 100 mg/kg dose was necessary to suppress consumption of palatable chow and of sucrose and saccharin solutions in nondeprived animals. Intraperitoneally TRP did not induce a conditioned taste aversion; thus, its anorexigenic effects were unrelated to sickness/malaise. c-Fos mapping in feeding-related brain sites revealed TRP-induced changes in the dorsal vagal complex, hypothalamic paraventricular and supraoptic nuclei and in the basolateral amygdala. TRP enhanced activation of hypothalamic neurons synthesizing an anorexigen, oxytocin (OT). Pharmacological blockade of the OT receptor with a blood-brain barrier -penetrant antagonist, L-368,899, attenuated TRP-induced decrease in deprivation-induced chow intake, but not in thirst-driven water consumption. We conclude that TRP triggers anorexigenic action and underlying neural responses even when it does not directly contact the gut mucosa. TRP requires OT to decrease energy intake, whereas OT is nonobligatory in TRP's effects on drinking behavior.

Stereoselective effects of the second-generation synthetic cathinone α-pyrrolidinopentiophenone (α-PVP): assessments of conditioned taste avoidance in rats

Work with α-pyrrolidinopentiophenone (α-PVP), a second-generation synthetic cathinone, has been generally limited to the racemate. Given that with other synthetic cathinones, there are behavioral and neurochemical differences between their enantiomers, differences may also be seen with α-PVP. The present study assessed the relative contribution of each enantiomer to the aversive effects of racemic-α-PVP by comparing their ability to induce a conditioned taste avoidance. Adult male Sprague-Dawley rats were exposed every other day for four exposures to a novel saccharin solution followed immediately by an injection of 0 (saline vehicle) or 1.5, 3, or 6mg/kg of S-, R-, or racemic-α-PVP (IP). On alternating days, all subjects were given access to water to assess any unconditioned effects of α-PVP on general fluid consumption. Rats injected with the racemate and S-isomer of α-PVP displayed avoidance of the drug-associated saccharin solution, although this avoidance was dose-dependent only for the subjects injected with the racemate. There was no evidence of taste avoidance in animals injected with the R-enantiomer at any dose tested. Animals injected with 3mg/kg racemic-α-PVP did not differ in avoidance from those treated with 1.5mg/kg of the S-enantiomer, but subjects treated with 6mg/kg racemic-α-PVP displayed a significantly stronger avoidance than those treated with 3mg/kg S-α-PVP. The present work suggests that the aversive effects of racemic α-PVP are mediated primarily by its S-isomer. The fact that at the highest dose tested (6mg/kg), the racemate induces an avoidance greater than the simple additive effects of the S- and R-isomers (at 3mg/kg) suggests that while the R-isomer may not induce taste avoidance at this dose, it may interact synergistically with the S-isomer in mediating the effects of the racemic mixture. These results were discussed in terms of similar effects with other behavioral and physiological endpoints reported with a number of psychostimulants and suggest that the enantiomers of α-PVP are an important variable in characterizing its behavioral effects.

Inhibiting gustatory thalamus or medial amygdala has opposing effects on taste neophobia.

Taste neophobia is a feeding system defense mechanism that limits consumption of an unknown, and therefore potentially dangerous, edible until the post-ingestive consequences are experienced. We found that transient pharmacological inhibition (induced with the GABA agonists baclofen and muscimol) of the gustatory thalamus (GT; Experiment 1), but not medial amygdala (MeA; Experiment 2), during exposure to a novel saccharin solution attenuated taste neophobia. In Experiment 3 we found that inhibition of MeA neurons (induced with the chemogenetic receptor hM4DGi) enhanced the expression of taste neophobia whereas excitation of MeA neurons (with hM3DGq) had no influence of taste neophobia. Overall, these results refine the temporal involvement of the GT in the occurrence of taste neophobia and support the hypothesis that neuronal excitation in the GT is necessary for taste neophobia. Conversely, we show that chemogenetically, but not pharmacologically, inhibiting MeA neurons is sufficient to exaggerate the expression of taste neophobia.

The effects of amygdala and cortical inactivation on taste neophobia.

The current study examined the effects of transient inactivation of the basolateral amygdala (BLA; Experiment 1) and gustatory cortex (GC; Experiment 2) on the expression of taste neophobia and its recovery. We found that inactivation (induced by infusions of baclofen/muscimol) of each structure before exposure to a novel saccharin (0.5%) solution elevated intake on Trial 1 (i.e., taste neophobia was attenuated) and, surprisingly, decreased intake on Trial 2. It seems unlikely that this intake reduction on Trial 2 can be attributed to taste aversion learning caused by drug infusions because in the subsequent experiments with the same set of the implanted animals, the rats did not decrease intake when baclofen/muscimol was infused after taste presentation on Trial 1. The latter result suggests that BLA or GC inactivation that attenuates taste neophobia may also impair memory consolidation of a safe taste experience.

Drug Seeking and Relapse: New Evidence of a Role for Orexin and Dynorphin Co-transmission in the Paraventricular Nucleus of the Thalamus.

The long-lasting vulnerability to relapse remains the main challenge for the successful treatment of drug addiction. Neural systems that are involved in processing natural rewards and drugs of abuse overlap. However, neuroplasticity that is caused by drug exposure may be responsible for maladaptive, compulsive, and addictive behavior. The orexin (Orx) system participates in regulating numerous physiological processes, including energy metabolism, arousal, and feeding, and is recruited by drugs of abuse. The Orx system is differentially recruited by drugs and natural rewards. Specifically, we found that the Orx system is more engaged by drugs than by non-drugs, such as sweetened condensed milk (SCM) or a glucose saccharin solution (GSS), in an operant model of reward seeking. Although stimuli (S+) that are conditioned to cocaine (COC), ethanol, and SCM/GSS equally elicited reinstatement, Orx receptor blockade reversed conditioned reinstatement for drugs vs. non-drugs. Moreover, the hypothalamic recruitment of Orx cells was greater in rats that were tested with the COC S+ vs. SCM S+, indicating of a preferential role for the Orx system in perseverative, compulsive-like COC seeking and not behavior that is motivated by palatable food. Accumulating evidence indicates that the paraventricular nucleus of the thalamus (PVT), which receives major Orx projections, mediates drug-seeking behavior. All Orx neurons contain dynorphin (Dyn), and Orx and Dyn are co-released. In the VTA, they play opposing roles in reward and motivation. To fully understand the physiological and behavioral roles of Orx transmission in the PVT, one important consideration is that Orx neurons that project to the PVT may co-release Orx with another peptide, such as Dyn. The PVT expresses both Orx receptors and κ opioid receptors, suggesting that Orx and Dyn act in tandem when released in the PVT, in addition to the VTA. The present review discusses recent findings that suggest the maladaptive recruitment of Orx/Dyn-PVT neurotransmission by drugs of abuse vs. a highly palatable food reward.

Effects of combined brief etomidate anesthesia and postnatal stress on amygdala expression of Cl− cotransporters and corticotropin-releasing hormone and alcohol intake in adult rats

Early life stressors, including general anesthesia, can have adverse effects on adult neural and behavioral outcomes, such as disruptions in inhibitory signaling, stress responsivity and increased risk of psychiatric disorders. Here we used a rat model to determine the effects of combined exposure to etomidate (ET) neonatal anesthesia and maternal separation on adult amygdala expression of genes for corticotropin-releasing hormone (Crh) and the chloride co-transporters Nkcc1 and Kcc2, as well as ethanol intake. Male and female Sprague-Dawley rats were subjected to 2 h of ET anesthesia on postnatal days (P) 4, 5, or 6 followed by maternal separation for 3 h on P10 (ET + SEP). During the P91-P120 period rats had daily 2 h access to three 0.05% saccharin solutions containing 0%, 5%, or 10% ethanol, followed by gene expression analyses. The ET + SEP group had increased Crh mRNA levels and Nkcc1/Kcc2 mRNA ratios in the amygdala, with greater increases in Nkcc1/Kcc2 mRNA ratios in males. A moderate increase in 5% ethanol intake was evident in the ET + SEP males, but not females, after calculation of the ratio of alcohol intake between the last week and first week of exposure. In contrast, control males tended to decrease alcohol consumption during the same period. A brief exposure to ET combined with a subsequent episode of stress early in life induced significant alterations in expression of amygdala Crh, Nkcc1 and Kcc2 with greater changes in the Cl− transporter expression in males. The possibility of increased alcohol intake in the exposed males requires further confirmation using different alcohol intake paradigms.