ORCID Profile
0000-0003-3337-6402
Current Organisation
University of Technology Sydney
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Behavioural neuroscience | Animal Cell and Molecular Biology | Biological psychology | Biological Psychology (Neuropsychology, Psychopharmacology, Physiological Psychology) | Psychology | Nutritional science |
Nutrition | Expanding Knowledge in the Biological Sciences | Expanding Knowledge in Psychology and Cognitive Sciences |
Publisher: Royal Society of Chemistry (RSC)
Date: 2019
DOI: 10.1039/C9AN01300H
Abstract: A sandwich immunosensor was successfully developed for monitoring of interleukin-1β (IL-1β) in rat whole blood.
Publisher: Elsevier BV
Date: 12-2011
DOI: 10.1016/J.BBR.2011.07.058
Abstract: Adolescence is a critical developmental period during which chronic stress and binge alcohol consumption are often seen as environmental risk factors that confer vulnerability to later mental health problems. The current study modelled this using a 2×2 design where male Wistar rats were exposed to intermittent predatory stress (Stress condition: groups of 4 rats given 30 min of cat fur exposure in a large arena, once every 48 h) or intermittent alcohol (Alcohol condition: access to beer for 24 h every 2nd day), or both manipulations given on alternate days (Stress/Alcohol), or no manipulation (Control). The manipulations occurred over a 24 day adolescent window (postnatal day (PND) 33-57) giving a total of 12 cat fur exposures and/or 12 alternate days of beer access. Residual anxiety- and depressive-like behaviours were assessed in early adulthood (PND 58-77). Cat fur exposure was found to elicit a distinct defensive response in which groups of adolescent rats huddled together in the corner of the arena, either in "quads" (all 4 rats bunched together) or "triplets" (3 rats together and one outlier rat). Few approaches to the cat fur occurred and locomotor activity was suppressed relative to Control rats placed in the arena without fur. Huddling continued over the 12 repeated exposures to cat fur, and was temporarily exaggerated when fur from a novel cat was introduced. Interestingly, huddling and conditioned fear in the fur-associated context were most pronounced in rats receiving intermittent alcohol, suggesting that alternate day exposure to alcohol had anxiogenic effects, possibly linked to a hangover state on these days. Predatory stress did not affect overall alcohol consumption relative to rats given alcohol alone, but significantly inhibited weight gain through adolescence and into adulthood. In early adulthood, rats exposed to stress in adolescence, regardless of alcohol exposure, showed significantly reduced immobility in the forced swim test and signs of increased sociability with a novel conspecific in a social interaction paradigm. Overall, these findings suggest greater resilience in adulthood after chronic adolescent stress, indicating that coping with predators may be in some ways a form of early environmental enrichment.
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.APPET.2016.05.011
Abstract: The claim that non-nutritive sweeteners accelerate body weight gain by disrupting sweet-calorie associations was tested in two experiments using rats. The experiments were modelled on a key study from a series of experiments reporting greater body weight gain in rats fed yoghurt sweetened with saccharin than with glucose (Swithers & Davidson, 2008). Both of the current experiments likewise compared groups fed saccharin- or glucose-sweetened yoghurt in addition to chow and water, while Experiment 1 included a third group (Control) given unsweetened yoghurt. In Experiment 1, but not in Experiment 2, rats were initially exposed to both saccharin- and glucose-sweetened yoghurts to assess their relative palatability. We also tested whether the provision of an energy-dense sweet biscuit would augment any effects of saccharin on food intake and weight gain, as seemingly predicted by Swithers and Davidson (2008). In Experiment 1 there were no differences in body weight gain or fat pad mass between the Saccharin and Control group, whereas the Glucose group was the heaviest by the final 5 weeks and at cull had the largest fat pads. Greater acceptance of saccharin predicted more weight gain over the whole experiment. Consistent with past reports, fasting blood glucose and insulin measures did not differ between the Saccharin and Control groups, but suggested some impairment of insulin sensitivity in the Glucose group. Experiment 2 found similar effects of glucose on fat mass, but not on body weight gain. In summary, adding saccharin had no detectable effects on body-weight regulation, whereas the effects of glucose on fat pad mass were consistent with previous studies reporting more harmful effects of sugars compared to non-nutritive sweeteners.
Publisher: MDPI AG
Date: 27-01-2022
DOI: 10.3390/IJMS23031442
Abstract: Maternal obesity increases the risk of health complications in offspring, but whether these effects are exacerbated by offspring exposure to unhealthy diets warrants further investigation. Female Sprague-Dawley rats were fed either standard chow (n = 15) or ‘cafeteria’ (Caf, n = 21) diets across pre-pregnancy, gestation, and lactation. Male and female offspring were weaned onto chow or Caf diet (2–3/sex/litter), forming four groups behavioural and metabolic parameters were assessed. At weaning, offspring from Caf dams were smaller and lighter, but had more retroperitoneal (RP) fat, with a larger effect in males. Maternal Caf diet significantly increased relative expression of ACACA and Fasn in male and female weanling liver, but not CPT-1, SREBP and PGC1 PPARα was increased in males from Caf dams. Maternal obesity enhanced the impact of postweaning Caf exposure on adult body weight, RP fat, liver mass, and plasma leptin in males but not females. Offspring from Caf dams appeared to exhibit reduced anxiety-like behaviour on the elevated plus maze. Hepatic CPT-1 expression was reduced only in adult males from Caf fed dams. Post weaning Caf diet consumption did not alter liver gene expression in the adult offspring. Maternal obesity exacerbated the obesogenic phenotype produced by postweaning Caf diet in male, but not female offspring. Thus, the impact of maternal obesity on adiposity and liver gene expression appeared more marked in males. Our data underline the sex-specific detrimental effects of maternal obesity on offspring.
Publisher: Elsevier BV
Date: 09-2019
Publisher: MDPI AG
Date: 04-05-2023
DOI: 10.3390/NU15092191
Abstract: Background: Consumption of sugar-sweetened beverages (SSBs) forms the primary source of added sugar intake and can increase the risk of metabolic disease. Evidence from studies in humans and rodents also indicates that consumption of SSBs can impair performance on cognitive tests, but that removing SSB access can ameliorate these effects. Methods: The present study used an unblinded 3-group parallel design to assess the effects of a 12-week intervention in which young healthy adults (mean age = 22.85, SD = 3.89 mean BMI: 23.2, SD = 3.6) who regularly consumed SSBs were instructed to replace SSB intake with artificially-sweetened beverages (n = 28) or water (n = 25), or (c) to continue SSB intake (n = 27). Results: No significant group differences were observed in short-term verbal memory on the Logical Memory test or the ratio of waist circumference to height (primary outcomes), nor in secondary measures of effect, impulsivity, adiposity, or glucose tolerance. One notable change was a significant reduction in liking for strong sucrose solutions in participants who switched to water. Switching from SSBs to ‘diet’ drinks or water had no detectable impact on cognitive or metabolic health over the relatively short time frame studied here. This study was prospectively registered with the Australian New Zealand Clinical Trials Registry (ACTRN12615001004550 Universal Trial Number: U1111-1170-4543).
Publisher: Wiley
Date: 21-11-2023
Abstract: Maternal obesity increases the risk of health complications in children, highlighting the need for effective interventions. A rat model of maternal obesity to examine whether a diet switch intervention could reverse the adverse effects of an unhealthy postweaning diet is used. Male and female offspring born to dams fed standard chow or a high-fat, high-sugar "cafeteria" (Caf) diet are weaned onto chow or Caf diets until 22 weeks of age, when Caf-fed groups are switched to chow for 5 weeks. Adiposity, gut microbiota composition, and place recognition memory are assessed before and after the switch. Body weight and adiposity fall in switched groups but remain significantly higher than chow-fed controls. Nonetheless, the diet switch improves a deficit in place recognition memory observed in Caf-fed groups, increases gut microbiota species richness, and alters β ersity. Modeling indicate that adiposity most strongly predicts gut microbiota composition before and after the switch. Maternal obesity does not alter the effects of switching diet on metabolic, microbial, or cognitive measures. Thus, a healthy diet intervention lead to major shifts in body weight, adiposity, place recognition memory, and gut microbiota composition, with beneficial effects preserved in offspring born to obese dams.
Publisher: American Psychological Association (APA)
Date: 2015
DOI: 10.1037/XAN0000046
Abstract: In this article, schedule-induced drinking (SID) refers to increased drinking by hungry rats exposed to intermittent delivery of food pellets. Two major accounts of SID differ in their explanation of why such drinking tends be concentrated soon after pellet delivery. Temporal discrimination theories propose that drinking is a form of displacement activity that occurs when a pellet is least likely. Adventitious reinforcement theories propose that drinking is displaced to early in an interpellet interval (IPI) by magazine-directed behavior that occurs toward the end of an IPI. The main aim of this study was to examine the latter response-competition account by recording distributions of both licking and magazine entries as SID developed when pellets were delivered to different groups either on a fixed-time (FT 30 s) or on a variable-time schedule (VT 30 s), as in Experiment 1. Although VT 30-s schedules produced essentially flat distributions of magazine entries, licking still tended to be concentrated early in an IPI. Furthermore, there was no indication (Experiments 1 and 2) that magazine entry distributions developed ahead of licking distributions. Experiment 3 examined distributions of lever presses instead of licks: Initially high rates of lever pressing declined both with response-independent schedules (FT and VT) and when a minimal response-dependency was introduced (recycling conjunctive schedule), yet this response also tended to be most frequent soon after pellet delivery. Overall, the data were generally consistent with temporal conditioning theories.
Publisher: Wiley
Date: 05-05-2023
Abstract: The effects of diet cycling on cognition and fecal microbiota are not well understood. Adult male Sprague‐Dawley rats were cycled between a high‐fat, high‐sugar “cafeteria” diet (Caf) and regular chow. The impairment in place recognition memory produced by 16 days of Caf diet was reduced by switching to chow for 11 but not 4 days. Next, rats received 16 days of Caf diet in 2, 4, 8, or 16‐day cycles, each separated by 4‐day chow cycles. Place recognition memory declined from baseline in all groups and was impaired in the 16‐ versus 2‐day group. Finally, rats received 24 days of Caf diet continuously or in 3‐day cycles separated by 2‐ or 4‐day chow cycles. Any Caf diet access impaired cognition and increased adiposity relative to controls, without altering hippoc al gene expression. Place recognition and adiposity were the strongest predictors of global microbiota composition. Overall, diets with higher Caf chow ratios produced greater spatial memory impairments and larger shifts in gut microbiota species richness and beta ersity. Results suggest that diet‐induced cognitive deficits worsen in proportion to unhealthy diet exposure, and that shifting to a healthy chow for at least a week is required for recovery under the conditions tested here.
Publisher: Elsevier BV
Date: 07-2012
DOI: 10.1016/J.BEPROC.2012.03.014
Abstract: In many prey species aggregation of in iduals is a defensive strategy commonly employed in response to predators and predator-related cues. However, very little work has explored this adaptive response in laboratory rats. It is known that in idual rats show characteristic defensive responses to predator odors, such as hiding, avoidance, inhibition of foraging, feeding and reproduction, and risk assessment directed toward the odor source. However, whether these species-typical responses in in iduals are altered in the presence of other conspecifics is yet to be characterized. The present study therefore examined the defensive response of groups of two rats (dyads) or four rats (quads) to two unconditioned stressors: bright ambient light and cat odor (a 2g ball of cat fur). The dyads and quads were formed from familiar cage mates and test sessions (20 min) occurred in a large open arena (1200 mm(2)) to which the rats had been extensively habituated under dark conditions. The results showed that when quads of rats were exposed to either cat odor or bright light in this arena, they showed characteristic increases in close social proximity, termed "huddling". A tight grouping of 3 (triplet) or 4 (quad) rats was commonly seen in response to cat fur, while triplets were more commonly seen in response to bright light. Interestingly there was no evidence for increased social proximity in dyads exposed to either stressor, only in quads. However, cat odor caused other signs of fear (such as decreased locomotor activity and increased defecation) in both quads and dyads. It is concluded that huddling is a rodent defensive strategy in rats when anxiogenic stimuli are encountered by larger groups of rats.
Publisher: MyJove Corporation
Date: 11-2019
DOI: 10.3791/60262
Abstract: Obesity is rapidly increasing in incidence in developed and developing countries and is known to induce or exacerbate many diseases. The health burden of obesity and its comorbid conditions highlight the need for better understanding of its pathogenesis, yet ethical constraints limit studies in humans. To this end externally valid models of obesity in laboratory animals are essential for the understanding of being overweight and obesity. While many species have been used to model the range of changes that accompany obesity in humans, rodents are most commonly used. Our laboratory has developed a western-style cafeteria diet that consistently leads to considerable weight gain and markers of metabolic disease in rodents. The diet exposes rodents to a variety of highly palatable foods to induce hyperphagia, modeling the modern western food environment. This diet rapidly induces weight gain and body fat accumulation in rats allowing for the study of effects of overeating and obesity. While the cafeteria diet may not provide the same control over macronutrient and micronutrient profile as purified high-fat or high-fat, high-sugar diets, the cafeteria diet typically induces a more severe metabolic phenotype than that observed with purified diets and is more in line with metabolic disturbances observed in the overweight and obese human population.
Publisher: Elsevier BV
Date: 09-2021
Publisher: Wiley
Date: 10-08-2019
DOI: 10.1111/EJN.14518
Abstract: Chronic neuropathic pain and psychological stress interact to compromise goal-directed control over behaviour following mild psychological stress. The dorsomedial (DMS) and dorsolateral (DLS) striatum in the rat are crucial for the expression of goal-directed and habitual behaviours, respectively. This study investigated whether changes in monoamine levels in the DMS and DLS following nerve injury and psychological stress reflect these behavioural differences. Neuropathic pain was induced by a chronic constriction injury (CCI) of the sciatic nerve in Sprague-Dawley rats. Acute stress was induced using a 15-min restraint. Behavioural flexibility was assessed using the outcome devaluation paradigm. Noradrenaline, serotonin, dopamine and associated metabolites were measured bilaterally from the DLS and DMS. In uninjured rats, restraint increased dopaminergic markers in the left and serotonergic markers in the right of both the DMS and DLS, indicating a possible left hemisphere-mediated dominance. CCI led to a slightly different lateralised effect, with a larger effect in the DMS than in the DLS. In idual differences in behavioural flexibility following CCI negatively correlated with dopaminergic markers in the right DLS, but positively correlated with these markers in the left DMS. A combination of CCI and restraint reduced behavioural flexibility, which was associated with the loss of the left/DMS dominance. These data suggest that behavioural flexibility following psychological stress or pain is associated with a left hemisphere dominance within the dorsal striatum. The loss of behavioural flexibility following the combined stressors is then associated with a transition from left to right, and DMS to DLS dominance.
Publisher: Public Library of Science (PLoS)
Date: 18-09-2012
Publisher: Frontiers Media SA
Date: 11-01-2021
Publisher: Elsevier BV
Date: 06-2014
DOI: 10.1016/J.APPET.2014.02.011
Abstract: In the context of the well-documented metabolic and behavioural effects of supplementing rats' diets with access to a sucrose solution, the aim of this study was to compare the impact of 10% sucrose with that of an isoenergetic (10.4%) solution of hydrolysed starch, maltodextrin. This polysaccharide is metabolised at least as rapidly as sucrose and is also very palatable to rats, but does not contain fructose. Each of three experiments contained three groups: one given a sucrose solution, one given a maltodextrin solution and a control group maintained on standard chow and water alone. In Experiment 1 the sucrose and maltodextrin groups were given their supplementary drinks for 2 h each day, while in Experiments 2 and 3 these groups had 24-h access to their supplements. Ad libitum access to maltodextrin produced at least as rapid weight gain as sucrose and in Experiment 2 retroperitoneal fat mass was greater in the two carbohydrate groups than in the control group. Moreover, in Experiment 3, impaired performance on a location recognition task was also found in both carbohydrate groups after only 17 days on the diets. These results indicate that the harmful effects of excess sucrose consumption can also be produced by another rapidly absorbed carbohydrate that does not contain fructose.
Publisher: Springer Science and Business Media LLC
Date: 21-02-2019
DOI: 10.1038/S41598-019-38938-4
Abstract: Disrupted serotonin neurotransmission has been implicated in the etiology of psychopathic traits. Empirical research has found that people with high levels of psychopathic traits have a deficit in reinforcement learning that is thought to be linked with amygdala dysfunction. Altered serotonin neurotransmission provides a plausible explanation for amygdala dysfunction in psychopathic traits and recent research suggests that this may be associated with serotonin 1B (5-HT 1B ) receptor function. This research used an animal model to test the hypothesis that 5-HT 1B receptors are involved in the encoding of the specific features of reinforcing outcomes. An outcome devaluation task was used to test the effect of the systemic administration of a selective 5-HT 1B receptor agonist administered before encoding of “action-outcome” associations. Results showed that while administration of a 5-HT 1B receptor agonist allowed rats to acquire instrumental responding for food, when the content of that learning was further probed using an outcome devaluation task, performance differed from controls. 5-HT 1B agonism impaired learning about the specific sensory qualities of food rewards associated with distinct instrumental responses, required to direct choice performance when the value of one outcome changed. These findings suggest a role for 5-HT 1B receptor function in the encoding of the specific features of reinforcing outcomes.
Publisher: Clinical Exercise Physiology Association
Date: 12-2021
DOI: 10.31189/2165-6193-10.4.142
Abstract: It is known that exercise is beneficial to people with substance use disorder, however little evidence exists regarding their exercise capacity. This pilot study investigates the exercise capacity of patients with substance use disorder and effects of an acute bout of exercise on affect. Twenty-nine participants admitted to a withdrawal management facility were recruited to complete a health and exercise assessment (18 females, 11 males 41 ± 11 years old). Mood was measured before and after exercise assessments using the subjective experience to exercise scale. Data was grouped by sex, and descriptive analyses were performed against age-matched normative data. Within group, before and after subjective experience to exercise scale measures were analyzed using 2-way ANOVA with sex as a between subject factor. Participants ranged from having 2 to 6 modifiable cardiovascular risk factors. Participants performed below average compared to age-matched and sex-matched normative data for the 6-minute walk test (females: 539 ± 54 m, males: 606 ± 89 m) and push-up test (females: 22% good, males: 36% good). Of the 29 participants, 29% failed to achieve the average range for sex-matched norms in the sit-to-stand test. However, all participants achieved above average for curl-ups, and 72% achieved an average or above score in the step-up test. Exercise significantly increased wellbeing (P & 0.001, effect size = 1.12) and decreased psychological distress (P = 0.045, effect size = 1.03) and fatigue (P & 0.001, effect size = 1.32). Exercise is both feasible and beneficial in a withdrawal management setting. Capacity to perform exercise was generally poor with high in idual variance. Design of future interventions will need tailored prescription for patients in this population.
Publisher: Springer Science and Business Media LLC
Date: 07-12-2013
DOI: 10.1007/S00394-012-0475-5
Abstract: Rats given sugar-sweetened drinks can develop glucose intolerance, insulin resistance and dyslipidaemia. The aim of this study was to investigate whether such metabolic disruptions and also possible weight gain induced by chronic sucrose consumption could be attenuated by low-volume exercise. Using a 2 × 2 factorial design, rats were given free access for 57 days to either a 10% sucrose solution (Suc and SucEx) or water only (Con and ConEx), while exercise rats (SucEx and ConEx) received 20-min treadmill training every 3 days. Caloric intake and body weight were measured throughout this dietary intervention. Oral glucose tolerance tests were performed on days 29 and 54. Plasma insulin, triglycerides and leptin were also measured, together with post-mortem measures of retroperitoneal fat pads and liver triglycerides. In groups given sucrose, exercise reduced calorie consumption, reduced weight gain and decreased leptin relative to non-exercised controls. Exercise was found to improve glucose tolerance and insulin action at day 29, but not day 54. Low-volume exercise can be effective in preventing weight gain in sucrose-fed rats, probably via reduction of subcutaneous fat, but prevention of the glucose intolerance and dyslipidaemia produced by sucrose consumption may be transient.
Publisher: Elsevier BV
Date: 02-2021
Publisher: Elsevier BV
Date: 05-2014
DOI: 10.1016/J.PHYSBEH.2014.03.021
Abstract: The metabolic consequences of providing rats with extended access to sugar solutions have varied across studies. The two experiments in this study examined the effects of 8 weeks of 24-h access to 10% sucrose solution on adult Wistar rats. This was followed by 6 weeks of food restriction with no access to sucrose during which the behavioural effects of prior sucrose consumption on reward-oriented behaviour (Experiment 1) and reversal learning (Experiment 2) were assessed. In a comparison between rat strains, Experiment 1 found that sucrose accelerated weight gain in Albino but not Hooded Wistar rats, while sucrose-fed rats of both strains exhibited elevated fasting blood glucose and resistance to insulin. Importantly, at cull retroperitoneal fat deposits were elevated in sucrose-fed rats, at which point glucose and insulin had resolved to control levels and liver triglyceride content did not differ between groups. Experiment 2 also found that retroperitoneal fat content was higher in sucrose-fed rats at cull, after 6 weeks of behavioural testing without sucrose and with restricted access to food, and found a similar effect for epididymal fat. Behavioural testing in Experiment 1 found that sucrose exposure had no effect on habit formation assessed using an outcome devaluation paradigm. However, instrumental responding by sucrose-fed Albino rats was the least affected by pre-feeding, indicating a relationship between sucrose-induced obesity and food-seeking behaviour. In Experiment 2, sucrose-fed and control rats did not differ on a discrimination reversal task. In conclusion, this study demonstrates that the behavioural and metabolic effects of sucrose consumption vary with strain. Further, results indicate that sucrose consumption can lead to lasting increases in adipose tissue stores, a finding which has significant implications for human diets.
Publisher: MDPI AG
Date: 15-01-2021
DOI: 10.3390/NU13010240
Abstract: The widespread consumption of ‘western’-style diets along with sedentary lifestyles has led to a global epidemic of obesity. Epidemiological, clinical and preclinical evidence suggests that maternal obesity, overnutrition and unhealthy dietary patterns programs have lasting adverse effects on the physical and mental health of offspring. We review currently available preclinical and clinical evidence and summarise possible underlying neurobiological mechanisms by which maternal overnutrition may perturb offspring cognitive function, affective state and psychosocial behaviour, with a focus on (1) neuroinflammation (2) disrupted neuronal circuities and connectivity and (3) dysregulated brain hormones. We briefly summarise research implicating the gut microbiota in maternal obesity-induced changes to offspring behaviour. In animal models, maternal obesogenic diet consumption disrupts CNS homeostasis in offspring, which is critical for healthy neurodevelopment, by altering hypothalamic and hippoc al development and recruitment of glial cells, which subsequently dysregulates dopaminergic and serotonergic systems. The adverse effects of maternal obesogenic diets are also conferred through changes to hormones including leptin, insulin and oxytocin which interact with these brain regions and neuronal circuits. Furthermore, accumulating evidence suggests that the gut microbiome may directly and indirectly contribute to these maternal diet effects in both human and animal studies. As the specific pathways shaping abnormal behaviour in offspring in the context of maternal obesogenic diet exposure remain unknown, further investigations are needed to address this knowledge gap. Use of animal models permits investigation of changes in neuroinflammation, neurotransmitter activity and hormones across global brain network and sex differences, which could be directly and indirectly modulated by the gut microbiome.
Publisher: Elsevier BV
Date: 10-2016
DOI: 10.1016/J.PHYSBEH.2016.05.050
Abstract: Following previous results indicating that low acceptance of saccharin-sweetened yoghurt was associated with slower weight gain, the aim of this experiment was to determine which of three measures of in idual differences would predict subsequent chow consumption, body weight gain, and fat mass. Pre-test measures consisted of amount of running in an activity wheel, amount of 0.1% saccharin solution consumed over 24h, and performance on an elevated plus maze (EPM). Rats were then maintained for three weeks on a diet of standard chow and water. Subsequent post-testing repeated the procedures used in pre-testing. The rats were then culled and fat pads excised and weighed. Pre-testing revealed a negative correlation between saccharin acceptance and activity, while neither measure correlated with anxiety in the EPM. Pre-test saccharin acceptance was positively correlated with subsequent chow consumption, percent weight gain, and g/kg fat mass. Multiple regression analyses including all three pre-test measures confirmed saccharin acceptance as a predictor of chow consumption and, marginally, of fat pad mass, while high anxiety predicted low percent body weight gain.
Publisher: Elsevier BV
Date: 05-2018
DOI: 10.1016/J.PHYSBEH.2018.02.008
Abstract: High consumption of sugar-sweetened beverages (SSBs) is a risk factor for weight gain and metabolic disease. Whether this risk is reduced by switching to 'diet' beverages containing low-calorie sweeteners (LCS) is controversial. Two experiments modeled whether a switch from SSB to LCS beverages produced positive outcomes on behavioral and metabolic measures. Both experiments consisted of a Stage 1, in which adult female rats received unrestricted access to 10% sucrose solution in addition to chow and water for 4 (Experiment 1) or 8 weeks (Experiment 2). In Stage 2 rats were switched to either saccharin (Suc-Sacch) or water (Suc-Water) or remained on 10% sucrose (Suc-Suc) for a further 4 (Experiment 1) or 7 weeks (Experiment 2). Experiment 2 contained a fourth group that was maintained on water throughout (Water-Water). In both experiments energy intake and weight gain in Stage 2 was reduced for Suc-Sacch and Suc-Water groups relative to the Suc-Suc groups and at cull the Suc-Suc groups showed poorer insulin sensitivity and greater g/kg fat than Suc-Water and Suc-Sacch groups. In Experiment 2 short-term place recognition memory was impaired at the end of Stage 1 but recovered to a similar extent in the Suc-Water and Suc-Sacch groups when the latter groups were compared with the Water-Water group, recovery was found to be essentially complete. A higher saccharin concentration in Experiment 2 than in Experiment 1 increased absolute amounts of saccharin ingested but intake solution volumes remained low. These results show that switching from sucrose to either water or saccharin produces equivalent improvements on both metabolic and cognitive measures.
Publisher: Springer Science and Business Media LLC
Date: 18-09-2019
DOI: 10.1038/S41598-019-50113-3
Abstract: Repeated ‘cycling’ between healthy and unhealthy eating is increasingly common but the effects of such cycling on cognitive function are unknown. Here we tested the effects of cycling between chow and a cafeteria diet (CAF) rich in saturated fat and refined carbohydrates on fat mass and place recognition memory in rats. Rats fed the chow diet (control group) were compared with groups fed CAF for either: 3 consecutive days per week followed by 4 days of chow, (3CAF:4CHOW group) 5 consecutive days per week followed by 2 days of chow (5CAF:2CHOW group) or 7 days per week (7CAF group). Total days of exposure to CAF were matched between the latter groups by staggering the introduction of CAF diet. After 16–18 days of CAF, spatial recognition memory was significantly worse in the 7CAF group relative to controls. After 23–25 days of CAF, both the 7CAF and 5CAF:2CHOW groups, but not the 3CAF:4CHOW group, were impaired relative to controls, mirroring changes in fat mass measured by EchoMRI. CAF feeding did not affect object recognition memory or total exploration time. These results indicate that even when matching total exposure, the pattern of access to unhealthy diets impairs spatial memory in a graded fashion.
Publisher: Public Library of Science (PLoS)
Date: 02-07-2015
Publisher: Elsevier BV
Date: 06-2017
DOI: 10.1016/J.BBR.2017.04.003
Abstract: Chronic neuropathic pain often leads to impaired cognition and reduced behavioural flexibility. This study used a rat model to investigate if a peripheral nerve injury, with or without an additional acute psychological stress, alters behavioural flexibility and goal directed behaviour as measured by sensitivity to devaluation. Neuropathic pain was induced by a chronic constriction injury (CCI) of the sciatic nerve. CCI, sham-injury and naïve rats were trained to press two levers for two rewards. In outcome devaluation tests, one of the rewards was devalued by pre-feeding it to satiety, immediately prior to an extinction test measuring responding on the two levers. The ability to preferentially direct responding toward the action earning the currently-valued reward was taken as evidence of goal-directed behaviour. To test the impact of acute stress, rats were subjected to 15min restraint following pre-feeding and prior to the devaluation test. Neither CCI surgery nor acute stress alone altered sensitivity to devaluation, but in combination CCI and acute stress significantly reduced sensitivity to devaluation. This Study demonstrates that relatively mild stressors that are without effect in uninjured populations can markedly impair cognition under conditions of chronic pain. It further suggests that overlapping neural substrates regulated by nerve injury and/or acute stress are having a cumulative effect on behavioural flexibility.
Publisher: Elsevier BV
Date: 09-2014
DOI: 10.1016/J.APPET.2014.04.028
Abstract: The pronounced global rise in sugar consumption in recent years has been driven largely by increased consumption of sugar-sweetened beverages. Although high sugar intakes are recognised to increase the risk of obesity and related metabolic disturbances, less is known about how sugar might also impair cognition and learned behaviour. This review considers the effects of sugar in rodents on measures of learning and memory, reward processing, anxiety and mood. The parallels between sugar consumption and addictive behaviours are also discussed. The available evidence clearly indicates that sugar consumption can induce cognitive dysfunction. Deficits have been found most consistently on tasks measuring spatial learning and memory. Younger animals appear to be particularly sensitive to the effects of sugar on reward processing, yet results vary according to what reward-related behaviour is assessed. Sugar does not appear to produce long-term effects on anxiety or mood. Importantly, cognitive impairments have been found when intake approximates levels of sugar consumption in people and without changes to weight gain. There remain several caveats when extrapolating from animal models to putative effects of sugar on cognitive function in people. These issues are discussed in conjunction with potential underlying neural mechanisms and directions for future research.
Publisher: American Psychological Association (APA)
Date: 2018
DOI: 10.1037/XAN0000159
Abstract: Cue-potentiated feeding (CPF) describes the stimulation of food consumption by cues that have become associated with food. Determining under what Conditions CPF occurs is important to better understand how exposure to food cues contributes to overeating. CPF is typically found to be specific: cues enhance consumption only of the food they have signaled. Further, previous research has focused largely on discrete cues rather than multimodal cues such as a feeding environment. The present experiments paired a "Plus" context with highly palatable food and a "Minus" context with no food or chow in adult female rats. Experiment 1 confirmed that the Plus context enhanced consumption of the paired food (Froot Loops) but not a different food (banana bread). Experiments 2 and 3 tested whether pairing a variety of foods with the Plus context would overcome this specificity. In Experiment 2 the Plus context either contained bland chow (Chow group), 1 (Single group), or 3 palatable foods (Variety group). The test food, Froot Loops, was familiar but never paired with the Plus context. The Variety group exhibited CPF by eating more Froot Loops in the Plus than in the Minus context, while Single and Chow groups ate equivalently in the 2 contexts. Experiment 3 replicated this effect when the Minus context contained chow during training and when a novel food was tested. These findings have important implications for overeating given that modern food environments are typified by variety and that food consumption often occurs outside the home. (PsycINFO Database Record
Publisher: Elsevier BV
Date: 08-2013
DOI: 10.1016/J.PHYSBEH.2013.08.012
Abstract: Although increasing consumption of sugar drinks is recognized as a significant public health concern, little is known about (a) the cognitive effects resulting from sucrose consumption and (b) whether the long-term effects of sucrose consumption are more pronounced for adolescents. This experiment directly compared performance on a task of spatial learning and memory (the Morris Water Maze) and sensitivity to outcome devaluation following 28 days of 2-h/day access to a 10% sucrose solution in adolescent and young-adult Wistar rats. Sucrose groups developed elevated fasting blood glucose levels after the diet intervention, despite drawing <15% of calories from sucrose and gaining no more weight than controls. In subsequent behavioral testing, sucrose groups were impaired on the Morris Water Maze, with some residual deficits in spatial memory observed more than 6 weeks after the end of sucrose exposure. Further, results from outcome devaluation testing indicated that in the older cohort of rats, those fed sucrose showed reduced sensitivity to devaluation of the outcome, suggestive of differences in instrumental learning following sucrose exposure. Data provide strong evidence that sucrose consumption can induce deficits in spatial cognition and reward-oriented behavior at levels that resemble patterns of sugar drink consumption in young people, and which can remain long after exposure.
Publisher: Cold Spring Harbor Laboratory
Date: 31-03-2023
DOI: 10.1101/2023.03.29.534845
Abstract: Obesity can disrupt how food-predictive stimuli control action performance and selection. These two forms of control recruit cholinergic interneurons (CIN) located in the nucleus accumbens core (NAcC) and shell (NAcS), respectively. Given that obesity is associated with insulin resistance in this region, we examined whether interfering with CIN insulin signaling disrupts how food-predictive stimuli control actions. To interfere with insulin signaling we used a high-fat diet (HFD) or genetic excision of insulin receptor (InsR) from cholinergic cells. HFD left intact the capacity of food-predictive stimuli to energize performance of an action earning food when mice were tested hungry. However, it allowed this energizing effect to persist when the mice were tested sated. This persistence was linked to NAcC CIN activity but was not associated with distorted CIN insulin signaling. Accordingly, InsR excision had no effect on how food-predicting stimuli control action performance. Next, we found that neither HFD nor InsR excision altered the capacity of food-predictive stimuli to guide action selection. Yet, this capacity was associated with changes in NAcS CIN activity. These results indicate that insulin signaling on accumbal CIN does not modulate how food-predictive stimuli control action performance and selection. However, they show that HFD allows food-predictive stimuli to energize performance of an action earning food in the absence of hunger.
Publisher: Elsevier BV
Date: 2022
DOI: 10.1016/J.APPET.2021.105742
Abstract: Obesity is associated with changes to taste perception and brain reward circuitry. It is important to understand how these effects alter the preference for palatable foods and drinks, given that these are widely consumed, and leading risk factors for obesity. This study examined the effects of diet-induced obesity on sweet taste preference by analysing the microstructure of licking for sugar solutions and assessing pERK expression in the nucleus accumbens shell and insula. Adult male Sprague-Dawley rats were fed standard chow (Control n = 16) or a varied, palatable cafeteria diet (Caf n = 16) for 12 weeks. Two-choice preference tests between 2%, 8% and 32% sucrose solutions were conducted at baseline and in weeks 11-12 of the diet. Rats in the Caf group trebled energy intake and doubled weight gain relative to controls. In tests held under water restriction after 11 weeks of diet, the Control group reliably preferred higher sucrose concentrations (i.e., 32% > 8% > 2%). Relative to controls, the Caf group showed a stronger preference for 32% vs. 2% sucrose, lower preference for 32% vs. 8% sucrose, and were indifferent to 8% vs. 2% sucrose. Testing without water restriction increased preference for higher sucrose concentrations in both groups. Chronic Caf diet increased the latency to lick, decreased total licks and reduced alternations between spouts, but did not alter lick cluster size, a measure of hedonic appraisal, on any test. Following a final exposure to a novel sucrose concentration, neuronal activity (pERK) in the insula and nucleus accumbens shell was significantly reduced in the Caf group. Results indicate that differences in 'liking' do not underlie obesity-induced changes to sweet taste preference.
Publisher: MDPI AG
Date: 28-08-2020
DOI: 10.3390/BIOMEDICINES8090313
Abstract: Peripheral neuropathy (PN) is a debilitating complication of diabetes that affects % of patients. Recent evidence suggests that obesity and metabolic disease, which often precede diabetes diagnosis, may influence PN onset and severity. We examined this in a translationally relevant model of prediabetes induced by a cafeteria (CAF) diet in Sprague–Dawley rats (n = 15 CAF versus n = 15 control). Neuropathy phenotyping included nerve conduction, tactile sensitivity, intraepidermal nerve fiber density (IENFD) and nerve excitability testing, an in vivo measure of ion channel function and membrane potential. Metabolic phenotyping included body composition, blood glucose and lipids, plasma hormones and inflammatory cytokines. After 13 weeks diet, CAF-fed rats demonstrated prediabetes with significantly elevated fasting blood glucose, insulin and impaired glucose tolerance as well as obesity and dyslipidemia. Nerve conduction, tactile sensitivity and IENFD did not differ however, superexcitability was significantly increased in CAF-fed rats. Mathematical modeling demonstrated this was consistent with a reduction in sodium–potassium pump current. Moreover, superexcitability correlated positively with insulin resistance and adiposity, and negatively with fasting high-density lipoprotein cholesterol. In conclusion, prediabetic rats over-consuming processed, palatable foods demonstrated altered nerve function that preceded overt PN. This work provides a relevant model for pathophysiological investigation of diabetic complications.
Publisher: Frontiers Media SA
Date: 08-11-2016
Start Date: 10-2022
End Date: 09-2025
Amount: $387,000.00
Funder: Australian Research Council
View Funded ActivityStart Date: 12-2023
End Date: 12-2026
Amount: $456,106.00
Funder: Australian Research Council
View Funded Activity