Flexibility In Mice Research Articles

Sex-dependent differences in the ability of nicotine to modulate discrimination learning and cognitive flexibility in mice.

Nicotine, an addictive compound found in tobacco, functions as an agonist of nicotinic acetylcholine receptors (nAChRs) in the brain. Interestingly, nicotine has been reported to act as a cognitive enhancer in both human subjects and experimental animals. However, its effects in animal studies have not always been consistent, and sex differences have been identified in the effects of nicotine on several behaviors. Specifically, the role that sex plays in modulating the effects of nicotine on discrimination learning and cognitive flexibility in rodents is still unclear. Here, we evaluated sex-dependent differences in the effect of daily nicotine intraperitoneal (i.p.) administration at various doses (0.125, 0.25, and 0.5 mg/kg) on visual discrimination (VD) learning and reversal (VDR) learning in mice. In male mice, 0.5 mg/kg nicotine significantly improved performance in the VDR, but not the VD, task, while 0.5 mg/kg nicotine significantly worsened performance in the VD, but not VDR task in female mice. Furthermore, 0.25 mg/kg nicotine significantly worsened performance in the VD and VDR task only in female mice. Next, to investigate the cellular mechanisms that underlie the sex difference in the effects of nicotine on cognition, transcriptomic analyses were performed focusing on the medial prefrontal cortex tissue samples from male and female mice that had received continuous administration of nicotine for 3 or 18 days. As a result of pathway enrichment analysis and protein-protein interaction analysis using gene sets of differentially expressed genes, decreased expression of postsynaptic-related genes in males and increased expression of innate immunity-related genes in females were identified as possible molecular mechanisms related to sex differences in the effects of nicotine on cognition in discrimination learning and cognitive flexibility. Our result suggests that nicotine modulates cognitive function in a sex-dependent manner by alternating the expression of specific gene sets in the medial prefrontal cortex.

Acute inhibition of iron-sulfur cluster biosynthesis disrupts metabolic flexibility in mice.

Acute ISC inhibition leads to rapid loss of adiposity in miceMulti-metabolic pathway disruption upon ISC deficiency blocks energy storageNfs1 inhibition induces glucose dyshomeostasis due to ISC deficiency in β-cellsEnergy distress caused by inhibition of ISC synthesis is attenuated in aged mice.

Sedentary behavior in mice induces metabolic inflexibility by suppressing skeletal muscle pyruvate metabolism.

Carbohydrates and lipids provide the majority of substrates to fuel mitochondrial oxidative phosphorylation. Metabolic inflexibility, defined as an impaired ability to switch between these fuels, is implicated in a number of metabolic diseases. Here, we explore the mechanism by which physical inactivity promotes metabolic inflexibility in skeletal muscle. We developed a mouse model of sedentariness, small mouse cage (SMC), that, unlike other classic models of disuse in mice, faithfully recapitulated metabolic responses that occur in humans. Bioenergetic phenotyping of skeletal muscle mitochondria displayed metabolic inflexibility induced by physical inactivity, demonstrated by a reduction in pyruvate-stimulated respiration (JO2) in the absence of a change in palmitate-stimulated JO2. Pyruvate resistance in these mitochondria was likely driven by a decrease in phosphatidylethanolamine (PE) abundance in the mitochondrial membrane. Reduction in mitochondrial PE by heterozygous deletion of phosphatidylserine decarboxylase (PSD) was sufficient to induce metabolic inflexibility measured at the whole-body level, as well as at the level of skeletal muscle mitochondria. Low mitochondrial PE in C2C12 myotubes was sufficient to increase glucose flux toward lactate. We further implicate that resistance to pyruvate metabolism is due to attenuated mitochondrial entry via mitochondrial pyruvate carrier (MPC). These findings suggest a mechanism by which mitochondrial PE directly regulates MPC activity to modulate metabolic flexibility in mice.

Optogenetic stimulation of corticostriatal circuits improves behavioral flexibility in mice with prenatal alcohol exposure

Fetal alcohol spectrum disorder (FASD) is the most common preventable form of developmental and neurobehavioral disability. Animal models have demonstrated that even low to moderate prenatal alcohol exposure (PAE) is sufficient to impair behavioral flexibility in multiple domains. Previously, utilizing a moderate limited access drinking in the dark paradigm, we have shown that PAE 1) impairs touchscreen pairwise visual reversal in male adult offspring 2) leads to small but significant decreases in orbitofrontal (OFC) firing rates 3) significantly increases dorsal striatum (dS) activity and 4) aberrantly sustains OFC-dS synchrony across early reversal. In the current study, we examined whether optogenetic stimulation of OFC-dS projection neurons would be sufficient to rescue the behavioral inflexibility induced by PAE in male C57BL/6J mice. Following discrimination learning, we targeted OFC-dS projections using a retrograde adeno-associated virus (AAV) delivered to the dS which expressed channel rhodopsin (ChR2). During the first four sessions of reversal learning, we delivered high frequency optogenetic stimulation to the OFC via optic fibers immediately following correct choice responses. Our results show that optogenetic stimulation significantly reduced the number of sessions, incorrect responses, and correction errors required to move past the early perseverative phase for both PAE and control mice. In addition, OFC-dS stimulation during early reversal learning reduced the increased sessions, correct and incorrect responding seen in PAE mice during the later learning phase of reversal but did not significantly alter later performance in control ChR2 mice. Taken together these results suggest that stimulation of OFC-dS projections can improve early reversal learning in PAE and control mice, and these improvements can persist even into later stages of the task days later. These studies provide an important foundation for future clinical approaches to improve executive control in those with FASD.This article is part of the Special Issue on “PFC circuit function in psychiatric disease and relevant models”.

Dietary Intake of Chromista Oil Alters Hepatic Metabolomic Profile of Mice With Excess Fat Mass.

Increasing dietary intake of fish oil is frequently recommended for decreasing the risk for cardiovascular diseases and improving metabolic health. We hypothesised that dietary intake of chromista oil (a marine food product and a rich source of long-chain n-3 polyunsaturated fatty acids) ameliorates metabolic impairments in mice with established excess adiposity. Three-to 4-week-old mice (male) were fed a control (n = 12) or a high-fat diet (HFD, n = 24) for 12 weeks to establish body fat mass. Then, mice on the HFD were assigned to 2 groups (n = 12 each) with 1 continuing being fed the HFD and the other fed the HFD with chromista oil for an additional 12 weeks. Intake of chromista oil did not affect body weight and body adiposity of the mice fed the HFD; mice fed the HFD had significantly more body weight and fat mass than control mice. The flattened daily oscillations of respiratory exchange ratio induced by the HFD were not changed by chromista oil intake. Intake of chromista oil significantly increased plasma concentration of insulin, the calculated value of HOMA-IR, and plasma concentration of adiponectin in the mice fed the HFD. However, blood glucose was unaffected by chromista oil. Transcription of genes encoding circadian rhythm and fatty acid metabolism of the 2 HFD-fed groups were similar. Untargeted metabolomic analysis showed that intake of chromista oil altered the hepatic metabolomic profile with substantial alterations in amino acid metabolism. Findings from this study indicate that dietary intake of chromista oil does not improve glucose homeostasis or alter the diminished metabolic flexibility in mice with excess adiposity induced by the HFD. argeted metabolomic analysis is warranted to investigate the effects of dietary chromista oil, as a source of n-3 poly unsaturated fatty acids, on metabolism in models of obesity.

Timed Sequence Task: A New Paradigm to Study Motor Learning and Flexibility in Mice.

Motor learning and flexibility allow animals to perform routine actions efficiently while keeping them flexible. A number of paradigms are used to test cognitive flexibility, but not many of them focus specifically on the learning of complex motor sequences and their flexibility. While many tests use operant or touchscreen boxes that offer high throughput and reproducibility, the motor actions themselves are mostly simple presses of a designated lever. To focus more on motor actions during the operant task and to probe the flexibility of these well trained actions, we developed a new operant paradigm for mice, the "timed sequence task." The task requires mice to learn a sequence of lever presses that have to be emitted in precisely defined time limits. After training, the required pressing sequence and/or timing of individual presses is modified to test the ability of mice to alter their previously trained motor actions. We provide a code for the new protocol that can be used and adapted to common types of operant boxes. In addition, we provide a set of scripts that allow automatic extraction and analysis of numerous parameters recorded during each session. We demonstrate that the analysis of multiple performance parameters is necessary for detailed insight into the behavior of animals during the task. We validate our paradigm in an experiment using the valproate model of autism as a model of cognitive inflexibility. We show that the valproate mice show superior performance at specific stages of the task, paradoxically because of their propensity to more stereotypic behavior.

Neuronal glutamate transporters control reciprocal inhibition and gain modulation in D1 medium spiny neurons.

Understanding the function of glutamate transporters has broad implications for explaining how neurons integrate information and relay it through complex neuronal circuits. Most of what is currently known about glutamate transporters, specifically their ability to maintain glutamate homeostasis and limit glutamate diffusion away from the synaptic cleft, is based on studies of glial glutamate transporters. By contrast, little is known about the functional implications of neuronal glutamate transporters. The neuronal glutamate transporter EAAC1 is widely expressed throughout the brain, particularly in the striatum, the primary input nucleus of the basal ganglia, a region implicated with movement execution and reward. Here, we show that EAAC1 limits synaptic excitation onto a population of striatal medium spiny neurons identified for their expression of D1 dopamine receptors (D1-MSNs). In these cells, EAAC1 also contributes to strengthen lateral inhibition from other D1-MSNs. Together, these effects contribute to reduce the gain of the input-output relationship and increase the offset at increasing levels of synaptic inhibition in D1-MSNs. By reducing the sensitivity and dynamic range of action potential firing in D1-MSNs, EAAC1 limits the propensity of mice to rapidly switch between behaviors associated with different reward probabilities. Together, these findings shed light on some important molecular and cellular mechanisms implicated with behavior flexibility in mice.

Bifidobacterium animalis subsp. lactis and arginine mixture intake improves cognitive flexibility in mice.

The relationship between intestinal microbiota and cognitive function has been investigated as one of the major topics within the intestinal microbiota-gut-brain axis. Although an increasing number of studies have demonstrated an improvement in learning and memory when using probiotics or prebiotics, to date, there are no studies that target the cognitive flexibility observed in the early stages of several neuropsychiatric diseases, including dementia. We have recently developed a novel behavioral task using the touchscreen operant system to assess cognitive flexibility. We found that the disruption of the intestinal microbiota in mice induced a decline in cognitive flexibility. In the present study, we investigated the effects of treatments consisting of Bifidobacterium animalis subsp. lactis and arginine (Bifal + Arg), which promote the production of intestinal bacterial polyamine, on cognitive flexibility in the mouse model. Male C57BL6 mice orally treated with Bifal + Arg three times a week gradually decreased the 1st-choice incorrect diagonal rate with repeated reversals compared with the control group. Furthermore, in serial reversal phases, Bifal + Arg-treated mice shifted to the behavior of choosing a new correct spot more quickly after the reversal, and this was faster with repeated reversals. These results indicate that this treatment adapts to change and improves cognitive flexibility. This is the first report to show that intestinal environmental control, including probiotics and prebiotics, improves cognitive flexibility in mice.

Chronic corticosterone improves perseverative behavior in mice during sequential reversal learning

BackgroundStressful life events can both trigger development of psychiatric disorders and promote positive behavioral changes in response to adversities. The relationship between stress and cognitive flexibility is complex, and conflicting effects of stress manifest in both humans and laboratory animals. ObjectiveTo mirror the clinical situation where stressful life events impair mental health or promote behavioral change, we examined the post-exposure effects of stress on cognitive flexibility in mice. MethodsWe tested female C57BL/6JOlaHsd mice in the touchscreen-based sequential reversal learning test. Corticosterone (CORT) was used as a model of stress and was administered in the drinking water for two weeks before reversal learning. Control animals received drinking water without CORT. Behaviors in supplementary tests were included to exclude non-specific confounding effects of CORT and improve interpretation of the results. ResultsCORT-treated mice were similar to controls on all touchscreen parameters before reversal. During the low accuracy phase of reversal learning, CORT reduced perseveration index, a measure of perseverative responding, but did not affect acquisition of the new reward contingency. This effect was not related to non-specific deficits in chamber activity. CORT increased anxiety-like behavior in the elevated zero maze test and repetitive digging in the marble burying test, reduced locomotor activity, but did not affect spontaneous alternation behavior. ConclusionCORT improved cognitive flexibility in the reversal learning test by extinguishing prepotent responses that were no longer rewarded, an effect possibly related to a stress-mediated increase in sensitivity to negative feedback that should be confirmed in a larger study.

Cognitive Flexibility in Mice: Effects of Puberty and Role of NMDA Receptor Subunits.

Cognitive flexibility refers to the ability to adapt flexibly to changing circumstances. In laboratory mice, we investigated whether cognitive flexibility is higher in pubertal mice than in adult mice, and whether this difference is related to the expression of distinct NMDA receptor subunits. Using the attentional set shifting task as a measure of cognitive flexibility, we found that cognitive flexibility was increased during puberty. This difference was more pronounced in female pubertal mice. Further, the GluN2A subunit of the NMDA receptor was more expressed during puberty than after puberty. Pharmacological blockade of GluN2A reduced the cognitive flexibility of pubertal mice to adult levels. In adult mice, the expression of GluN2A, GluN2B, and GluN2C in the orbitofrontal cortex correlated positively with performance in the attentional set shifting task, whereas in pubertal mice this was only the case for GluN2C. In conclusion, the present study confirms the observation in humans that cognitive flexibility is higher during puberty than in adulthood. Future studies should investigate whether NMDA receptor subunit-specific agonists are able to rescue deficient cognitive flexibility, and whether they have the potential to be used in human diseases with deficits in cognitive flexibility.

FreiBox: A Versatile Open-Source Behavioral Setup for Investigating the Neuronal Correlates of Behavioral Flexibility via 1-Photon Imaging in Freely Moving Mice.

To survive in a complex and changing environment, animals must adapt their behavior. This ability is called behavioral flexibility and is classically evaluated by a reversal learning paradigm. During such a paradigm, the animals adapt their behavior according to a change of the reward contingencies. To study these complex cognitive functions (from outcome evaluation to motor adaptation), we developed a versatile, low-cost, open-source platform, allowing us to investigate the neuronal correlates of behavioral flexibility with 1-photon calcium imaging. This platform consists of FreiBox, a novel low-cost Arduino behavioral setup, as well as further open-source tools, which we developed and integrated into our framework. FreiBox is controlled by a custom Python interface and integrates a new licking sensor (strain gauge lickometer) for controlling spatial licking behavioral tasks. In addition to allowing both discriminative and serial reversal learning, the Arduino can track mouse licking behavior in real time to control task events in a submillisecond timescale. To complete our setup, we also developed and validated an affordable commutator, which is crucial for recording calcium imaging with the Miniscope V4 in freely moving mice. Further, we demonstrated that FreiBox can be associated with 1-photon imaging and other open-source initiatives (e.g., Open Ephys) to form a versatile platform for exploring the neuronal substrates of licking-based behavioral flexibility in mice. The combination of the FreiBox behavioral setup and our low-cost commutator represents a highly competitive and complementary addition to the recently emerging battery of open-source initiatives.

Effects of binge drinking and the anti-inflammatory drug indomethacin on spatial memory and cognitive flexibility in mice

In previous research, we found that chronic-intermittent ethanol administration (CIEA), a model of binge drinking, impaired emotional memory in mice, and this impairment was counteracted by the anti-inflammatory drug indomethacin. In the present study, we evaluated the effects of CIEA on spatial memory and cognitive flexibility in adolescent mice of both sexes. Animals were randomly assigned to one of four groups for each sex: SS (saline + saline), SA (saline + alcohol), SI (saline + indomethacin), and AI (alcohol + indomethacin). They were injected with saline, ethanol (3 g/kg) or indomethacin (10 mg/kg) for the first three days of each week, throughout three weeks. 96 h after treatment, subjects learnt a standard water maze task on five consecutive days (4-day training and 1-day probe trial). One day later, mice underwent a reversal task for evaluating spatial cognitive flexibility. Animals receiving alcohol (SA and AI groups) did not differ from controls (SS groups) during the standard task, but animals treated with indomethacin performed better than controls, both in the acquisition trials and the probe trial. During the reversal task, no significant differences between alcohol groups and controls were observed, but the indomethacin group showed significant lower escape latencies than controls. No sex differences were found in either task. In conclusion, binge drinking does not impair spatial memory or spatial cognitive flexibility, while the anti-inflammatory indomethacin improves both, showing that the effects of alcohol and indomethacin on spatial memory (dependent on hippocampus) are different to those they exert on emotional memory (dependent on amygdala).

Effects of chronic tramadol administration on cognitive flexibility in mice.

Tramadol is widely used for pain relief especially in seniors. However, long-term use of tramadol has serious adverse effects, including cognitive impairment. Besides its memory effects, already demonstrated in animals, a recent clinical report suggests that tramadol could also affect executive function in seniors. Several studies have hypothesized that the anti-muscarinic properties of tramadol could be responsible for the deleterious effects of tramadol on cognition. We aimed at investigating the effects of chronic administration of tramadol on cognitive flexibility in adult male mice, as assessed by a visual discrimination reversal task using a touchscreen device. The effects of tramadol were further compared to those of scopolamine, a reference muscarinic antagonist. We found that, during the early phase of the reversal task, when cognitive flexibility is most in demand, both tramadol-treated mice (20mg/kg, s.c., twice a day) and scopolamine-treated mice (0.5mg/kg, s.c., twice a day) needed more correction trials and showed a higher perseveration index than saline-treated mice. Therefore, tramadol affects cognitive flexibility, and its anticholinergic properties could be at least partly involved in these deficits. In view of these deleterious cognitive effects of tramadol, physicians should be cautious when prescribing this analgesic, especially in seniors who are more vulnerable to adverse drug events and in which alternative prescription should be preferred whenever possible.

Importance of Adipose Tissue NAD+ Biology in Regulating Metabolic Flexibility.

Nicotinamide adenine dinucleotide (NAD+) is an essential coenzyme that regulates cellular energy metabolism in many cell types. The major purpose of the present study was to test the hypothesis that NAD+ in white adipose tissue (WAT) is a regulator of whole-body metabolic flexibility in response to changes in insulin sensitivity and with respect to substrate availability and use during feeding and fasting conditions. To this end, we first evaluated the relationship between WAT NAD+ concentration and metabolic flexibility in mice and humans. We found that WAT NAD+ concentration was increased in mice after calorie restriction and exercise, 2 enhancers of metabolic flexibility. Bariatric surgery-induced 20% weight loss increased plasma adiponectin concentration, skeletal muscle insulin sensitivity, and WAT NAD+ concentration in people with obesity. We next analyzed adipocyte-specific nicotinamide phosphoribosyltransferase (Nampt) knockout (ANKO) mice, which have markedly decreased NAD+ concentrations in WAT. ANKO mice oxidized more glucose during the light period and after fasting than control mice. In contrast, the normal postprandial stimulation of glucose oxidation and suppression of fat oxidation were impaired in ANKO mice. Data obtained from RNA-sequencing of WAT suggest that loss of NAMPT increases inflammation, and impairs insulin sensitivity, glucose oxidation, lipolysis, branched-chain amino acid catabolism, and mitochondrial function in WAT, which are features of metabolic inflexibility. These results demonstrate a novel function of WAT NAMPT-mediated NAD+ biosynthesis in regulating whole-body metabolic flexibility, and provide new insights into the role of adipose tissue NAD+ biology in metabolic health.

MicroRNA-210 Regulates Dendritic Morphology and Behavioural Flexibility in Mice.

MicroRNAs are known to be critical regulators of neuronal plasticity. The highly conserved, hypoxia-regulated microRNA-210 (miR-210) has been shown to be associated with long-term memory in invertebrates and dysregulated in neurodevelopmental and neurodegenerative disease models. However, the role of miR-210 in mammalian neuronal function and cognitive behaviour remains unexplored. Here we generated Nestin-cre-driven miR-210 neuronal knockout mice to characterise miR-210 regulation and function using in vitro and in vivo methods. We identified miR-210 localisation throughout neuronal somas and dendritic processes and increased levels of mature miR-210 in response to neural activity in vitro. Loss of miR-210 in neurons resulted in higher oxidative phosphorylation and ROS production following hypoxia and increased dendritic arbour density in hippocampal cultures. Additionally, miR-210 knockout mice displayed altered behavioural flexibility in rodent touchscreen tests, particularly during early reversal learning suggesting processes underlying updating of information and feedback were impacted. Our findings support a conserved, activity-dependent role for miR-210 in neuroplasticity and cognitive function.

Sequential reversal learning: a new touchscreen schedule for assessing cognitive flexibility in mice.

The widespread deficits in cognitive flexibility observed across psychiatric disorders call for improved rodent tests to understand the biology of cognitive flexibility and development of better psychotherapeutics. Current reversal learning paradigms have a forced-choice setup that challenges the interpretation of results. We aimed at developing a free-choice reversal learning test, where images are presented sequentially and animals are free to move, to enable investigation of the cognitive sub-processes that occur during reversal. Behavior in female C57BL/6JOlaHsd mice was characterized using chronic fluoxetine as a reference compound. Additional tests were included to support the interpretation of results and exclude confounding pharmacological effects. Behaviors in vehicle-treated mice were furthermore analyzed for relatedness to deepen the understanding of parameters measured. We found that exploitation of the previously rewarded image was independent of exploration and acquisition of the new reward contingency and could be differentially modulated by fluoxetine, supporting recent theories that these processes are not mutually exclusive. Specifically, fluoxetine reduced mistake rate, premature and perseverative responses, and promoted conservative strategies during reversal without affecting hit rate. These effects appeared to be most prominent during the late stage of reversal learning, where accuracy was above chance level. Analysis of behaviors in vehicle-treated mice suggested that exploitation was related to an impulsive-like deficit in response inhibition, while exploration was more related to motivation. This new schedule was feasible, easy to implement, and can provide a deeper understanding of the cognitive sub-processes during reversal.

Acute serotonin 2A receptor activation impairs behavioral flexibility in mice

Serotonin 2A (5-HT2A) receptors are the primary site of action of hallucinogenic drugs and the target of atypical antipsychotics. 5-HT2A receptors are also implicated in executive function, including behavioral flexibility. Previous studies showed that 5-HT2A receptor blockade improved behavioral flexibility in rodent models related to autism spectrum disorder and schizophrenia. The current study instead was conducted to examine the impact of acute 5-HT2A receptor activation on behavior flexibility in the control C57BL/6 J strain. Because of the therapeutic potential of serotonergic hallucinogens and the unknown impact of many of these compounds on cognition, the present study examined how the 5-HT2A/2C agonist 1-(2,5-dimethoxy-4-iodophenyl)-2-aminopropane (DOI) and the more selective 5-HT2A agonist 25CN-NBOH impacted behavioral flexibility in C57BL/6 J mice. Male mice were tested on a probabilistic spatial discrimination and reversal learning task after an intraperitoneal injection of vehicle, 2.5 mg/kg DOI, 1.0 mg/kg 25CN-NBOH, 1.0 mg/kg of the 5-HT2C receptor antagonist SER-082 or combined treatment with SER-082 (1.0 mg/kg) and 2.5 mg/kg DOI before testing of probabilistic reversal learning. All groups demonstrated comparable performance on the initial spatial discrimination, i.e. similar trials to criterion. DOI alone did not impair reversal learning, whereas 25CN-NBOH increased the number of trials to criterion during reversal learning. Because 5-HT2A and 5-HT2C receptors have been shown to functionally antagonize each other in several behavioral paradigms, we also tested whether blockade of 5-HT2C receptors would unmask 5-HT2A receptor activation by DOI and impair reversal learning. Mice treated with SER-082 in combination with DOI required significantly more trials to reach criterion. In an additional experiment, a dose response experiment with 25CN-NBOH revealed that the 1.0 mg/kg dose tested in reversal learning did not affect locomotor activity. Together, these findings indicate that activation of 5-HT2A receptors impairs probabilistic reversal learning and that 5-HT2A and 5-HT2C receptors exert opposing effects on behavioral flexibility in male mice.

TRPC3-Based Protein Signaling Complex as a Therapeutic Target of Myocardial Atrophy.

Transient receptor potential (TRP) channels, especially canonical TRP channel subfamily members 3 (TRPC3) and 6 (TRPC6), have gained attention as a putative therapeutic target of heart failure. Moreover, TRPC3 and TRPC6 channels are physiologically important for maintaining cellular homeostasis. How TRPC3/C6 channels alter intracellular signaling from adaptation to maladaptation, has been discussed for many years. We have recently shown that the formation of a protein signal complex between TRPC3 and NADPH oxidase (Nox) 2 caused by environmental stresses (e.g., hypoxia, nutritional deficiency, and anti-cancer drug treatment) promotes Nox2-dependent reactive oxygen species production and cardiac stiffness, including myocardial atrophy and interstitial fibrosis, in rodents. In fact, pharmacological prevention of the TRPC3 -Nox2 protein complex can maintain cardiac flexibility in mice after anti-cancer drug treatment. In this mini-review, we discuss the relationship between TRPC3/C6 channels and cardiovascular disease, and propose a new therapeutic strategy by focusing on pathology-specific protein-protein interactions.

Social isolation improves the performance of rodents in a novel cognitive flexibility task

BackgroundSocial isolation, i.e., the deprivation of social contact, is a highly stressful circumstance that affects behavioral and functional brain development in social animals. Cognitive flexibility, one of the essential executive brain function that facilitates survival problem solving, was reported to be impaired after social isolation rearing. However, most of the previous studies have focused on the constrained aspect of flexibility and little is known about the unconstrained aspect. In the present study, the unconstrained cognitive flexibility of Kunming mice (Mus musculus, Km) reared in isolation was examined by a novel digging task. The exploratory behavior of the mice was also tested utilizing the hole-board and elevated plus maze tests to explain the differences in cognitive flexibility between the mice reared socially and in isolation.ResultsThe results demonstrated that the isolated mice had a higher success rate in solving the novel digging problem and showed a higher rate of exploratory behavior compared with the controls. Linear regression analysis revealed that the time it took the mice to solve the digging problem was negatively associated with exploratory behavior.ConclusionsThe data suggest that social isolation rearing improves unconstrained cognitive flexibility in mice, which is probably related to an increase in their exploratory behavior. Such effects may reflect the behavioral and cognitive evolutionary adaptations of rodents to survive under complex and stressful conditions.

Metabolic Flexibility: Interplay of Diet Composition and Intermittent Fasting on Healthspan (P08-053-19)

Objectives4:10 periodic fasting schedule is proposed to improve biomarkers of healthspan through metabolic flexibility in mice on both standard and high fat diets. MethodsOur study adopted the 4:10 fasting schedule using the fasting-mimicking diet (FMD) as our model. FMD is a plant-based, low-protein, and low-sugar diet regime implemented for four days every two-week cycle. Its regenerative effect is observed in the refeeding phase following starvation, allowing for the breakdown of cells via increased autophagy. In comparison to stricter fasting regimes such as intermittent fasting, chronic caloric restriction, and periodic fasting, FMD is well-tolerated in the clinical setting. 74 12-month old C57BL/6 mice were randomized into two diet groups: standard diet or high-fat diet. For 4 days out of every fourteen days, the mice were severely caloric restricted and refed with ad-libitum of either standard or high fat diets for the remaining 10 days, matching the controls who were fixed on the ad-libitum diet. The 4:10 fasting schedule was repeated 11 times before the mice were sacrificed. To measure metabolic flexibility, metabolic cages, ELISA, and glucose meters were used. ResultsBody weight and composition, metabolic flexibility, and insulin sensitivity indicate differences between fasting on diet composition. Not only did those on the fasting high-fat diet (FHFD) remain overweight, identical to their HFD controls, insulin sensitivity was also attenuated in FHFD groups. Fasting standard diet (FSD) had a reduction of 5% in body weight and 15% in body fat. Carbohydrate and lipid metabolism differences indicated by the respiratory exchange ratio as well as motor function performance differences further support the positive impact of fasting on SD groups, not HFD groups. Characteristic of positive healthspan biomarkers, reduced leptin and improved insulin sensitivity was observed with FSD, not FHFD. ConclusionsWe found that while the FMD schedule improved healthspan as indicated by biomarkers of healthy aging for mice on the standard diet, it could not counteract the negative health effects of the obesogenic diet. These results demonstrate the importance of not only time of feeding but also diet composition in respect to healthspan. Funding SourcesNational Institute on Aging (NIA) – National Institutes of Health (NIH).