Hindbrain Double-Negative Feedback Mediates Palatability-Guided Food and Water Consumption.

Hunger and thirst have distinct goals but control similar ingestive behaviors, and little is known about neural processes that are shared between these behavioral states. We identify glutamatergic neurons in the peri-locus coeruleus (periLCVGLUT2 neurons) as a polysynaptic convergence node from separate energy-sensitive and hydration-sensitive cell populations. We develop methods for stable hindbrain calcium imaging in free-moving mice, which show that periLCVGLUT2 neurons are tuned to ingestive behaviors and respond similarly to food or water consumption. PeriLCVGLUT2 neurons are scalably inhibited by palatability and homeostatic need during consumption. Inhibition of periLCVGLUT2 neurons is rewarding and increases consumption by enhancing palatability and prolonging ingestion duration. These properties comprise a double-negative feedback relationship that sustains food or water consumption without affecting food- or water-seeking. PeriLCVGLUT2 neurons are a hub between hunger and thirst that specifically controls motivation for food and water ingestion, which is a factor that contributes to hedonic overeating and obesity.

Thirst and drugs: A study in the World Health Organization's pharmacovigilance database.

Thirst is a complex physiological compensatory mechanism but could also be associated with drugs. This association was poorly investigated previously. Using the WHO global pharmacovigilance database, Vigibase®, disproportionality analyses potential associations between exposure to drugs and thirst reports were performed. All reports of thirst in adults between 01/01/2000 and 31/12/2023 were included. Results are expressed as reporting odds ratio (ROR). Analysis of the 3186 reports of thirst (978 'serious') allowed, first, to confirm the association between thirst and exposure to vasopressin antagonists (tolvaptan), lithium, gliflozins (dapagliflozin, empagliflozin), pregabalin and antimuscarinic drugs (glycopyronium, oxybutynin, tiotropium). Second, new safety signals were described with monoamine reuptake inhibitors (antidepressants: duloxetine, venlafaxine; anti-obesity agent: sibutramine), antipsychotic (olanzapine), glucocorticoid (prednisolone), diuretic (furosemide) drugs as well with ribavirin or sodium oxybate. This study is the first to offer a list of drugs associated with thirst in humans.

Is increased subjective thirst associated with greater interdialytic weight gains, extracellular fluid and dietary sodium intake?

BACKGROUND: Some previous studies have reported an effect of increasing subjective thirst and interdialytic weight gains (IDWG), and that this may be influenced by nonadherence to dietary sodium restrictions, whereas others reported no such association. As such we wished to review the effect of self-reported thirst on IDWGs and dietary sodium intake. METHODS: Dialysis patients were asked to complete visual analogues thirst, distress thermometer (DT) scores and complete a sodium food frequency questionnaire (SFFQ). IDWG and pre and post dialysis volumes were measured with multifrequency bioelectrical impedance. RESULTS: One hundred and eleven patients completed the questionnaires and had bioimpedance measurements: 63% male, mean age 63.8 ± 16.1 years, 33% diabetic with a median thirst score 3 (0-5) and SFFQ 52.0 ± 18, and IDWG 2.1 ± 1.3%. Thirst was associated with DT (r = 0.28, p = 0.004) and negatively with age (r = -0.31, p < 0.001), but not SFFQ, IDWG, extracellular water, or dialysate sodium, or dialysate to plasma gradient. Patients with higher thirst scores were younger (58.0 ± 15.2 vs. 69.4 ± 15.0 years, p < 0.001) with higher DT scores (5 [2-7] vs. 2 [0-5], p < 0.001). On multivariate logistic analysis, only age was associated with self-reported thirst (odds ratio 0.95, 95% confidence limits 0.92-0.98, p < 0.001). CONCLUSION: We found that subjective thirst was greater for younger patients and those who reported higher levels of distress, but no association with IDWGs, dietary sodium intake, or dialysate sodium. However, most of our patients followed the dietary advice, as evidenced by the low SFFQ scores and % IDWGs. Whether thirst increases distress or distress increases subjective thirst remains to be determined.

Exploring thirst incidence and risk factors in patients undergoing general anesthesia after extubation based on ERAS principles: a cross sectional study.

BACKGROUND: This study aims to comprehend the levels of dry mouth and thirst in patients after general anesthesia, and to identify the factors influencing them. METHODS: The study included all patients transferred to the Post Anesthesia Care Unit (PACU) at the Second Affiliated Hospital of Dalian Medical University between August 2021 and November 2021 after undergoing general anesthesia. A thirst numeric rating scale was utilized to conduct surveys, enabling the assessment of thirst incidence and intensity. Statistical analysis was performed to explore patient thirst levels and the associated factors. RESULTS: The study revealed a thirst incidence rate of 50.8%. Among the thirst intensity ratings, 71.4% of patients experienced mild thirst, 23.0% reported moderate thirst, and 5.6% expressed severe thirst. Single-factor statistical analysis of potential risk factors among the enrolled cases indicated that gender, history of coronary heart disease, surgical duration, intraoperative fluid volume, intraoperative blood loss, intraoperative urine output, and different surgical departments were linked to post-anesthetic thirst in patients undergoing general anesthesia. Multifactorial Logistic regression analysis highlighted age, gender, history of coronary heart disease, fasting duration, and intraoperative fluid volume as independent risk factors for post-anesthetic thirst in patients undergoing general anesthesia. Moreover, age, gender, history of coronary heart disease, and intraoperative fluid volume were also identified as risk factors for varying degrees of thirst. CONCLUSION: The incidence and intensity of post-anesthetic thirst after general anesthesia are relatively high. Their occurrence is closely associated with age, gender, history of coronary heart disease, fasting duration, and intraoperative fluid volume.

Early oral hydration on demand in postanesthesia care unit effectively relieves postoperative thirst in patients after gynecological laparoscopy: a prospective randomized controlled trial.

BACKGROUND: Postoperative thirst is one of the most intense, common and easily ignored subjective discomforts in patients after gynecological surgery. This study aimed to investigate whether early oral hydration on demand in the postanesthesia care unit (PACU) after gynecological laparoscopy under general anesthesia can appease postoperative thirst and increase patient comfort. METHODS: Participants were randomized into the intervention and control groups. Patients in the intervention group were allowed to achieve early oral hydration on demand in the PACU if they were evaluated as fully conscious, with stable vital signs, grade 5 muscle strength, and well-recovered cough and swallowing reflex. However, the total amount of water intake throughout the entire study should not exceed 0.5mL/kg. During the study, the frequency of water intake, the total amount of water intake and adverse events were accurately recorded. The control group was managed according to the routine procedures and began to drink water 2 h after anesthesia. The intensity of thirst and subjective comfort in patients were assessed using the visual analog scale (VAS) when they entered and left the PACU. RESULTS: No statistically significant differences were identified in age, height, weight, body mass index, pre-operative fasting time, duration of surgery, intraoperative fluid intake, intraoperative blood loss, intraoperative urine volume, and thirst intensity and subjective comfort scores between the groups before intervention (P > 0.05). After intervention, the VAS score for thirst intensity in the intervention group significantly decreased (P < 0.05), and the VAS score for subjective comfort in the intervention group significantly increased (P < 0.05). No adverse events were detected in both groups during the entire study. CONCLUSION: Early oral hydration on demand in the PACU can safely and effectively relieve postoperative thirst in patients, and improve patient comfort after gynecological laparoscopy. TRIAL REGISTRATION: This single-center, prospective, randomized controlled trial was registered at the Chinese Clinical Trial Center on April 27, 2023. The registration number of this study is ChiCTR2300070985.

Parent-offspring similarity in hunger and thirst sensations.

The internal (i.e., interoceptive) sensations that characterise hunger vary between people, and this may also be the case for thirst, although it has not been so well explored. There are probably both heritable and learning-based causes for this interoceptive variability. Consequently, it would seem plausible that parents and their offspring would have more similar patterns of hunger and thirst than pairs of strangers. We tested this idea, in addition to exploring its potential moderating variables, by studying the similarity of self-reported hunger and thirst sensations in 170 students and their primary caregivers from childhood. Both students and caregivers completed the same online-survey, covering hunger and thirst sensations, beliefs about the causes of hunger and thirst, the Three Factor Eating Questionnaire (revised) and demographic data. We find evidence of robust student-caregiver similarity in interoceptive hunger and thirst sensations (medium effect sizes), with these being moderated by caregiver beliefs about the homeostatic nature of each state (medium effect sizes). This suggests a potential role for caregivers in the development of their offspring's interoceptive cues for hunger and for thirst. In addition, thirst, like hunger, appears to be multidimensional, and varies between people. The implications of these findings are discussed.

Rational regulation of water-seeking effort in rodents.

In the laboratory, animals' motivation to work tends to be positively correlated with reward magnitude. But in nature, rewards earned by work are essential to survival (e.g., working to find water), and the payoff of that work can vary on long timescales (e.g., seasonally). Under these constraints, the strategy of working less when rewards are small could be fatal. We found that instead, rats in a closed economy did more work for water rewards when the rewards were stably smaller, a phenomenon also observed in human labor supply curves. Like human consumers, rats showed elasticity of demand, consuming far more water per day when its price in effort was lower. The neural mechanisms underlying such "rational" market behaviors remain largely unexplored. We propose a dynamic utility maximization model that can account for the dependence of rat labor supply (trials/day) on the wage rate (milliliter/trial) and also predict the temporal dynamics of when rats work. Based on data from mice, we hypothesize that glutamatergic neurons in the subfornical organ in lamina terminalis continuously compute the instantaneous marginal utility of voluntary work for water reward and causally determine the amount and timing of work.

Evolution of the thirst mechanism in Homo: The need and limitations of thirst and hydration.

There is a view that the perception of thirst and actual body fluid balance may affect cognitive and exercise performance. The evolutionary evidence suggests that our survival was dependent on our ability to sweat profusely when hunting during the heat of the day (persistence hunting), so if water deficits were not tolerated, consequently the thirst mechanism would limit our persistence hunting capability. This also means that hunting and searching for water was undertaken with some extent of water deficit, and in turn suggests that performance; physical and cognitive, was conducted with a degree of dehydration. Given the current views on the maintenance of body water for performance, there is a need to evaluate the evidence relating to tolerance limits for water deficits with respect to both physical and cognitive performance. This review considers the thirst mechanism and the conditions and selective pressures under which this might have evolved. Consideration will be given to how the thirst mechanism influences our physical and cognitive performance. The review suggests that Homo developed appropriate tolerances for water deficits and thirst perception, with a safety margin that prevented detrimental declines in physical and cognitive performance to the point of inhibiting corrective action. This would have offered a selective advantage, enabling the search for water and functioning adequately during periods of water scarcity.

Nurses' experiences of ethical challenges concerning thirst in dying patients in specialist palliative care: a qualitative study.

AIM: To describe nurses' experiences of ethical challenges in relation to thirst in terminally ill patients in specialist palliative care units. RESEARCH DESIGN: A qualitative, reflexive thematic design with an inductive analysis was used. PARTICIPANTS AND RESEARCH CONTEXT: Eighteen qualitative interviews with nurses working in six different specialist palliative care units in different hospitals in Sweden were conducted. The interviews were transcribed verbatim and analysed with a reflexive thematic analysis. RESULTS: This study identified four themes that reflect ethical challenges experienced by nurses in the palliative care regarding thirst: Harmful infusions interfere with peaceful dying; conflict between tradition and personal experience; What is the right intervention to quench thirst? and; Lack of standard procedures, competence and interest among team members. CONCLUSION: Palliative care nurses experience a number ethical challenges in relation to thirst in dying patients. The main challenge is the provision of fluids to dying patients via artificial infusions, which nurses struggle with, as they do not want to interfere with a peaceful dying process.

Caregivers' Attention Toward, and Response to, Their Child's Interoceptive Hunger and Thirst Cues.

People can use their internal state to determine if they are hungry or thirsty. Although the meaning of some interoceptive cues may be innate (e.g., pain), it is possible that others-including those for hunger and thirst-are acquired. There has been little exploration of this idea in humans. Consequently, we conducted a survey among child caregivers to determine if the basic conditions necessary for interoceptive learning were present. Two-hundred and thirty-five caregivers of children aged 1-12 years were asked if they had recently noticed stomach rumbling, hunger-related irritability, and a dry mouth in their child. They were also asked how they would respond. The impact of several moderating variables, especially caregiver beliefs about the causes of hunger, fullness, and thirst, was also explored. Fifteen percent of caregivers had recently noticed stomach rumbling in their child, 28% hunger-related irritability, and 14% a dry mouth. Forty-four percent of caregivers had noticed at least one of these three cues. Noticing hunger cues was significantly moderated by caregiver beliefs about their cause, by child age, and in one case by temporal context (around vs. outside mealtimes). Key caregiver responses were providing the need (e.g., offer food) and/or asking the child if they had a need (e.g., hungry?). Each type of response could potentially support a different form of interoceptive learning. In conclusion, we suggest the necessary conditions for children to learn interoceptive hunger and thirst cues, are present in many caregiver-offspring dyads.

Thirst symptoms in patients with heart failure: An integrative review.

AIM: To identify the risk and protective factors affecting thirst symptoms in patients with heart failure (HF) and intervention strategies to alleviate thirst symptoms. DESIGN: An integrative review. METHODS: A total of 61 articles were retrieved. Screening yielded a total of 21 articles which were appraised for quality. The quality of studies was assessed using the Mixed Methods Appraisal Tool. DATA SOURCES: Ten electronic databases were searched in October 2023, including Embase, Pubmed, CINAHL, Cochrane, Web of Science, Wiley, CNKI, VIP, CBM and WanFang. In addition, we searched grey databases and manually searched reference lists of included and relevant reviews. RESULTS: In total, 1644 articles were retrieved, of which 21 were included. Eight studies addressed the factors. Six themes emerged as risk factors, including demographics, severity of disease, psycho-environmental, medication, fluid restriction and homeostasis. Conversely, an increase in fluid intake, a high score of sodium restriction diet attitude and using ARB were identified as protective factors. Thirteen studies focus on intervention strategies. Five unique intervention strategies were identified, including Traditional Chinese Medicine, mint-related interventions, sour-flavour interventions, improved water restriction and cluster nursing strategy. CONCLUSION: This finding identified the factors associated with thirst symptoms in patients with HF, especially concerning the elaboration of risk factors, which suggests that healthcare professionals should focus on the risk factors for thirst in patients with HF and consciously avoid the occurrence of these risk factors. Additionally, there are considerable cultural differences in interventions, therefore, to increase adherence during symptom management, careful selection of appropriate intervention strategies based on the requirements and preferences of patients is required. While there are some therapies, there aren't enough high-quality empirical investigations. Thus, multi-centre, large-sample studies are also required in subsequent research to demonstrate the interventions' effectiveness. IMPLICATIONS FOR THE PROFESSION: The nurse must notice the symptoms of thirst in HF to slow down the disease's progression and improve the patient's physical and emotional well-being. REPORTING METHOD: The review complies with the PRISMA guidelines for reporting systematic reviews. PATIENT OR PUBLIC CONTRIBUTION: No patient or public contribution.

Construction of an assessment scale for thirst severity in critically ill patients and its reliability and validity.

OBJECTIVE: Developing a severity assessment scale for critically ill patients' thirst and conducting reliability and validity tests, aiming to provide healthcare professionals with a scientific and objective tool for assessing the level of thirst. METHODS: Based on literature review and qualitative interviews, a pool of items was generated, and a preliminary scale was formed through two rounds of Delphi expert consultation. Convenience sampling was employed to select 178 ICU patients in a top-three hospital from May 2023 to October 2023 as the study subjects to examine the reliability and validity of the severity assessment scale for critically ill patients' thirst. RESULTS: The developed severity assessment scale for critically ill patients' thirst consists of 8 evaluation items and 26 evaluation indicators. The agreement coefficients for two rounds of expert consultation were 100% and 92.6% for the positive coefficient, and the authority coefficients were .900 and .906. Kendall's concordance coefficients were .101 and .120 (all p < .001). The overall Cronbach's α coefficient for the scale was .827. The inter-rater reliability coefficient was .910. The Item-Content Validity Index (I-CVI) ranged from .800 to 1.000, and the Scale-Content Validity Index/Average (S-CVI/Ave) was .950. CONCLUSION: The critically ill patients' thirst assessment scale is reliable and valid and can be widely used in clinical practice. PATIENT OR PUBLIC CONTRIBUTION: The AiMi Academic Services (www.aimieditor.com) for English language editing and review services. IMPLICATIONS FOR CLINICAL PRACTICE: The scale developed in this study is a simple and ICU-specific scale that can be used to assess the severity of thirst in critically ill patients. As such, the severity of thirst in critically ill patients can be evaluated quickly so that targeted interventions can be implemented according to the patient's specific disease and treatment conditions. Therefore, patient comfort can be improved, and thirst-related health problems can be prevented.

Nurses' perception of thirst in patients within palliative home care: a qualitative study.

BACKGROUND: Thirst is the body's natural urge to replenish fluids in response to a deficiency in hydration. Patients at the end of life gradually lose their independence and reach a point where they become unable to express their needs and can no longer drink on their own. In palliative care, the main advice is to provide regular oral care to relieve symptoms such as dry mouth and thirst. However, according to previous studies the prevalence of thirst and dry mouth remains. AIM: The aim of this study was to describe palliative care, nurses' views and experiences of thirst in end-of-life care in specialist palliative care units. METHODS: A qualitative interview study with an inductive approach was conducted. Eighteen nurses working in six different specialist palliative care units in different hospitals in Sweden were interviewed. The interviews were transcribed and analysed with a content analysis approach according to Graneheim and Lundman. RESULTS: When nurses discuss thirst, they perceive thirst as a problem for the patient. This is attributable to various factors, including the patient breathing with an open mouth, a reduced level of awareness, and negligence on the part of the nursing staff. Signs of thirst are dry mouth, and frequently and intense sucking on the oral care stick during oral care. It also emerged that not all nurses perceived that dying patients experienced thirst. They believe that thirst is something that is reduced in the dying patient in the same way as hunger. The most important thing to them is to relieve the dry mouth by providing good oral care. Several issues, such as a lack of guidelines paired with the patient's reduced consciousness and hence his/her lack of communication, make assessing thirst problematic. CONCLUSION: Nurses have different thoughts and experiences about thirst, where some perceive patients as thirsty while others perceive them as having a dry mouth. Nurses expressed that both evidence and guidelines are lacking.

The Effect of Cold Oral Applications in the Management of Postoperative Thirst: A Systematic Review.

PURPOSE: Thirst is one of the most bothersome symptoms experienced by surgical patients. Effective thirst intervention and management in the Post Anesthesia Care Unit (PACU) and hospital wards is critical because patients are less sedated and more aware than in the past. There is a need to review the literature on the identification and management of thirst in the inpatient and PACU settings. The aim of this systematic review was to examine the available evidence on the effectiveness of oral cold applications on thirst in postoperative patients. DESIGN: This was a systematic review study. Articles in PUBMED, Web of Science, ScienceDirect, TÜBITAK-ULAKBIM, and TRDizin databases between January 2008 and January 2023 that included oral cold applications to relieve the thirst of patients in the postoperative period were included. METHODS: The PICOT-SD (Patients Interventions Comparison Outcome Time-Study Design) method was used as an eligibility criterion for inclusion in the study. The eligibility criteria included that the articles were written in English-Turkish and within the target dates, the studies included nursing interventions, the primary outcome of the studies was thirst, and the study sample included postoperative patients. The risk of bias was assessed using the RoB2 tool developed by Cochrane. FINDINGS: A total of 254 articles were retrieved from the databases using the specified keywords. 244 articles did not meet the study criteria: 30 were excluded because they were not interventional studies, 61 were not conducted in a postoperative population, 56 were duplicates, and 79 were not on a related topic. A total of 10 studies consisting of randomized controlled trials and quasi-experimental articles met the criteria for our review. Oral cold applications effectively reduced the thirst rate of postoperative patients and improved their health-related quality of life. The intervention has also been shown to reduce other anesthesia-related complications. CONCLUSIONS: This systematic review concluded that cold oral applications have promising effects on thirst, dry mouth, and health-related quality of life. Cold oral applications are cost-effective and suitable for large-scale health care applications.

The Prevalence and Risk Factors for Postoperative Thirst: A Systematic Review and Meta-analysis.

PURPOSE: Thirst is a symptom of dehydration and one of the main complications affecting postoperative outcomes and comfort. Persistent water scarcity can have a detrimental effect on the cognitive function and psychology of patients. However, the current evidence about the prevalence and risk factors for postoperative thirst is not fully understood. Therefore, this study aims to investigate the prevalence and risk factors of postoperative thirst and provide guidance for clinical practice. DESIGN: Systematic review and meta-analysis. METHODS: We searched PubMed, Cochrane Library, Web of Science, Embase, Clinicaltrials.gov, China National Knowledge Infrastructure, and Wanfang Database. Eligible studies were evaluated using the Agency for Healthcare Research and Quality. The collected data were pooled and analyzed using Stata15.0. FINDINGS: A total of 11 cross-sectional studies were included involving 20,612 patients. Eight studies reported prevalence and the pooled prevalence of postoperative thirst was 76.8% (95% confidence interval [CI]: 0.664 to 0.858). Five studies contributed to meta-syntheses of risk factors for postoperative thirst. The results indicated that sex (odds ratio [OR] = 1.44, 95% CI = 1.13 to 1.84, I2 = 80.2%, P = .006), anesthesia drug (OR = 1.48, 95% CI = 1.06 to 2.06, I2 = 94.8%, P < .001), surgical type (OR = 0.66, 95% CI = 0.49 to 0.9, I2 = 77.9%, P = .004) were statistically associated with postoperative thirst. CONCLUSIONS: Our study shows a high prevalence of postoperative thirst. Sex, anesthesia drug, and surgical type are risk factors that influence postoperative thirst. Nurses and other health care professionals should routinely assess the postoperative thirst of patients and perform targeted interventions to alleviate their distressing symptoms and improve the quality of care.

The Effect of Oral Water and Ice Popsicle Exposure on the Management of Thirst in the Immediate Postoperative Period.

PURPOSE: Thirst is a high-incidence condition that causes patients to experience problems in the early postoperative period in the postanesthesia care unit (PACU). The study was conducted to determine the effect of oral water and ice application in managing early postoperative thirst. DESIGN: Randomized controlled trial. METHODS: The study was conducted between January and April 2017 with 150 patients who were transferred from the operating room of a university hospital to the PACU and met the research criteria. The patients were divided into treatment (water group = 50, ice group = 50) and control (n = 50) groups. Patients in the intervention group received oral water/ice application after admission to the PACU after surgery. Patients in the control group received routine treatment and care. FINDINGS: In intragroup comparisons before and after the application, there was a statistically significant decrease in thirst, dry mouth, dry throat, and difficulty in swallowing in the water and ice groups (P < .001); ice application was more effective than water application, and there was no significant difference in the control group (P > .05). CONCLUSIONS: Postoperative oral water/ice application was an effective and safe nursing intervention to reduce thirst, dry mouth, dry throat, and difficulty in swallowing. Ice application was more effective.

[The Comparative Effectiveness of Using Cold Water Oral Spray and Cold Saline Oral Spray for Thirst Relief in Patients With Endotracheal Intubation in the Intensive Care Unit].

BACKGROUND: Thirst is a common symptom among patients with endotracheal intubation in the intensive care unit (ICU), with an estimated prevalence of 88%. PURPOSE: This study was designed to compare the effectiveness of cold saline spray and cold water spray in alleviating thirst, and to explore the maintenance and sustained effects of both groups in relieving thirst among patients with endotracheal intubation in the ICU. METHODS: Patients with indwelling tracheal tubes in the medical ICU were recruited from one medical center in northern Taiwan and randomly assigned to either the cold saline (n = 18) or cold water (n = 18) group. The cold saline group received three rounds of cold saline spray at a temperature of 2°C - 8°C. Each round consisted of 10 sprays directed toward each of the four surfaces of the oral cavity followed by a 5-minute wait period. This process was repeated three times, with 30-minute intervals between interventions. The cold water group received the same intervention steps using a cold water spray at 2°C - 8°C. Thirst intensity was measured using a numeric rating scale before and after each of the three interventions in both groups. Demographic and relevant physiological data were collected on the participants by reviewing their medical records. RESULTS: Both of the interventions were found to effectively alleviate thirst intensity, with no significant difference between the two groups in terms of thirst intensity reduction after each intervention detected. Only the cold water spray had a maintenance effect, while the two groups had a continuous sustained effect in alleviating thirst intensity. CONCLUSIONS: Both of the interventions effectively alleviated thirst, and the cold water spray had both maintenance and sustained effects in alleviating thirst intensity. Based on the results, the cold water spray method may be considered as the priority treatment for thirst alleviation by healthcare providers in the clinical management of patients with tracheal intubation.

Behavioral responses of free-flying Drosophila melanogaster to shiny, reflecting surfaces.

Active locomotion plays an important role in the life of many animals, permitting them to explore the environment, find vital resources, and escape predators. Most insect species rely on a combination of visual cues such as celestial bodies, landmarks, or linearly polarized light to navigate or orient themselves in their surroundings. In nature, linearly polarized light can arise either from atmospheric scattering or from reflections off shiny non-metallic surfaces like water. Multiple reports have described different behavioral responses of various insects to such shiny surfaces. Our goal was to test whether free-flying Drosophila melanogaster, a molecular genetic model organism and behavioral generalist, also manifests specific behavioral responses when confronted with such polarized reflections. Fruit flies were placed in a custom-built arena with controlled environmental parameters (temperature, humidity, and light intensity). Flight detections and landings were quantified for three different stimuli: a diffusely reflecting matt plate, a small patch of shiny acetate film, and real water. We compared hydrated and dehydrated fly populations, since the state of hydration may change the motivation of flies to seek or avoid water. Our analysis reveals for the first time that flying fruit flies indeed use vision to avoid flying over shiny surfaces.

Vaptans or voluntary increased hydration to protect the kidney: how do they compare?

The adverse effects of vasopressin (AVP) in diverse forms of chronic kidney disease have been well described. They depend on the antidiuretic action of AVP mediated by V2 receptors (V2R). Tolvaptan, a selective V2R antagonist, is now largely used for the treatment of patients with autosomal dominant polycystic kidney disease. Another way to reduce the adverse effects of AVP is to reduce endogenous AVP secretion by a voluntary increase in fluid intake. These two approaches differ in several ways, including the level of thirst and AVP. With voluntary increased drinking, plasma osmolality will decline and so will AVP secretion. Thus, not only will V2R-mediated effects be reduced, but also those mediated by V1a and V1b receptors (V1aR and V1bR). In contrast, selective V2R antagonism will induce a loss of fluid that will stimulate AVP secretion and thus increase AVP's influence on V1a and V1b receptors. V1aR is expressed in the luminal side of the collecting duct (CD) and in inner medullary interstitial cells, and their activation induces the production of prostaglandins, mostly prostaglandin E2 (PGE2). Intrarenal PGE2 has been shown to reduce sodium and water reabsorption in the CD and increase blood flow in the renal medulla, both effects contributing to increase sodium and water excretion and reduce urine-concentrating activity. Conversely, non-steroidal anti-inflammatory drugs have been shown to induce significant water and sodium retention and potentiate the antidiuretic effects of AVP. Thus, during V2R antagonism, V1aR-mediated actions may be responsible for part of the diuresis observed with this drug. These V1aR-dependent effects do not take place with a voluntary increase in fluid intake. In summary, while both strategies may have beneficial effects, the information reviewed here leads us to assume that pharmacological V2R antagonism, with resulting stimulation of V1aR and increased PGE2 production, may provide greater benefit than voluntary high water intake. The influence of tolvaptan on the PGE2 excretion rate and the possibility to use somewhat lower tolvaptan doses than presently prescribed remain to be evaluated.

Effects of a low carbohydrate diet on heart failure symptoms and quality of life in patients with diabetic cardiomyopathy: A randomised controlled trial pilot study.

BACKGROUND AND AIMS: Heart failure, insulin resistance and/or type 2 diabetes mellitus coexist in the syndrome that is diabetic cardiomyopathy. Patients with diabetic cardiomyopathy experience high symptom burden and poor quality of life. We tested the hypothesis that a low carbohydrate diet improves heart failure symptoms and quality of life in patients with diabetic cardiomyopathy. METHODS AND RESULTS: We conducted a 16-week randomised controlled pilot trial comparing the effects of a low carbohydrate diet (LC) to usual care (UC) in 17 adult patients with diabetic cardiomyopathy. New York Heart Association classification, weight, thirst distress and quality of life scores as well as blood pressure and biochemical data were assessed at baseline and at 16 weeks. Thirteen (n = 8 LC; n = 5 UC) patients completed the trial. The low carbohydrate diet induced significant weight loss in completers (p = 0.004). There was a large between-group difference in systolic blood pressure at the end of the study (Hedges's g 0.99[-014,2.08]). There were no significant differences in thirst or quality of life between groups. CONCLUSION: This is the first clinical trial utilising the low carbohydrate dietary approach in patients with diabetic cardiomyopathy in an outpatient setting. A low carbohydrate diet can lead to significant weight loss in patients with diabetic cardiomyopathy. Future clinical trials with larger samples and that focus on fluid and sodium requirements of patients with diabetic cardiomyopathy who engage in a low carbohydrate diet are warranted. CLINICAL TRIAL REGISTRATION NUMBER: Australian New Zealand Clinical Trial Registry (ANZCTR): ACTRN12620001278921. DATE OF REGISTRATION: 26th November 2020.