Physiology & Behavior (PHYSIOL BEHAV)

Publications in this journal

• Article: Effect of Skipping Breakfast on Subsequent Energy Intake.

  David A Levitsky, Carly R Paconowski
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  ABSTRACT: The objective was to examine the effect of consuming breakfast on subsequent energy intake. Participants who habitually ate breakfast and those who skipped breakfast were recruited for two studies. Using a randomized crossover design , the first study, examined the effect of having participants consume either (a) no breakfast, (b) a high carbohydrate breakfast (335 kcals) or (c) a high fiber breakfast (360) kcals on three occasions and measured ad libitum intake at lunch. The second study again used a randomized crossover design but with a larger, normal carbyhydrate, breakfast consumed ad libtum. Intake averaged 624 kcals and subsequent food intake was measured throughout the day.Participants ate only foods served from the Cornell Human Metabolic Research Unit where all foods were weighed before and after consumption. In the first study, neither eating breakfast nor the kind of breakfast consumed had an effect on the amount consumed at lunch despite a reduction in hunger ratings. In the second study, intake at lunch as well as hunger ratings was significantly increased after skipping breakfast, by 144 Kcal, leaving a net caloric deficit of 408 Kcal by the end of the day.These data are consistent with published literature demonstrating that skipping a meal does not result in accurate energy compensation at subsequent meals and suggests that skipping breakfast may be an effective means to reduce daily energy intake in some adults.
  Physiology & Behavior 05/2013;
• Article: Comparison of cough reflex test against instrumental assessment of aspiration.

  Anna Miles, Sara Moore, Mary McFarlane, Fiona Lee, Jacqueline Allen, Maggie-Lee Huckabee
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  ABSTRACT: BACKGROUND: Silent aspiration is associated with pneumonia and mortality, and is poorly identified by traditional clinical swallowing evaluation (CSE). The aim of this study was to validate cough reflex testing (CRT) for identification of silent aspiration against aspiration confirmed by instrumental assessment. METHODS: Cough reflex threshold testing was completed on all patients using inhaled, nebulised citric acid. Within one hour, 80 patients underwent videofluoroscopic study of swallowing (VFSS) and 101 patients underwent fibreoptic endoscopic evaluation of swallowing (FEES). All tests were recorded and analysed by two researchers blinded to the result of the alternate test. RESULTS: Significant associations between CRT result and cough response to aspiration on VFSS (X(2) (2)=11.046, p=.003) and FEES (X(2) (2)=34.079, p<.001) were identified. Sensitivity and specificity were optimised at 0.6mol/L in patients undergoing VFSS (71%, 60% respectively) and at 0.4mol/L in patients undergoing FEES (69%, 71% respectively). A concentration of 0.8mol/L had the highest odds ratio (OR) for detecting silent aspiration (8 based on VFSS; 7 based on FEES). CONCLUSION: CRT results are significantly associated with aspiration response on instrumental assessment. Lower concentrations of citric acid provide a better predictive measure of silent aspiration. Clinical Trial Registration Information: Australian & New Zealand Clinical Trials Registry: URL; http://www.ANZCTR.org.au/ACTRN12613000007730.aspx, ACTRN: ACTRN12613000007730.
  Physiology & Behavior 05/2013;
• Article: Assessment of Social Interaction and Anxiety-Like Behavior in Senescence-Accelerated-Prone and -Resistant Mice.

  Harry C Meeker, Kathryn K Chadman, Agnes T Heaney, Richard I Carp
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  ABSTRACT: Two members of the senescence-accelerated mouse group, SAMP8 and SAMP10, are characterized by learning and memory deficits, while the SAMR1 strain is not. In this study, we used two behavioral tests, social approach and object recognition and compared the results observed for the SAMP strains with those seen in the control strain, SAMR1. In social approach experiments, the 2 SAMP strains showed decreased sociability compared to SAMR1 as shown by their reluctance to spend time near a stranger mouse and increased immobility. In object recognition experiments, SAMP strains spent more time in the thigmotaxis zone and less time in more exposed central zone than SAMR1 mice. From a behavioral standpoint, SAMP mice were less interactive and showed increased anxiety-like behavior compared to SAMR1.
  Physiology & Behavior 05/2013;
• Article: Concomitant docosahexaenoic acid administration ameliorates stress-induced cognitive impairment in rats.

  Emil Trofimiuk, Jan J Braszko
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  ABSTRACT: Long chain n-3 fatty acids, especially eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) may slow cognitive decline. DHA plays an important role in neural function and decreased plasma DHA are associated with cognitive decline in healthy elderly adults and in patients with Alzheimer's disease. In this study we tested a hypothesis that DHA protects cognitive functions of male Wistar rats against negative impact of prolonged restraint stress. Specifically, we attempted to characterize the preventive action of prolonged treatment with DHA enriched preparation (daily dose of DHA: 300mg/kg, p.o. for 21days) in comparison with positive control (fluoxetine: 10mg/kg daily, p.o. for 21days) against an impairment caused by chronic restraint stress (2h daily for 21days) on recognition memory tested in a object recognition task and on the spatial working memory tested in Morris water maze. We found that administration of DHA enriched preparation prevented deleterious effects of chronic restraint stress both on recognition (p<0.01) and on the working spatial memory (p<0.001).
  Physiology & Behavior 05/2013;
• Article: Enkephalin and dynorphin mRNA expression are associated with resilience or vulnerability to chronic social defeat stress.

  Patrick Bérubé, Sylvie Laforest, Seema Bhatnagar, Guy Drolet
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  ABSTRACT: There are important and enduring differences between individuals in the magnitude of all aspects of the stress response. Among the neuropeptide systems, the endogenous opioids enkephalin (ENK) and dynorphin (DYN), are very interesting candidates to participate in the naturally occurring variations in coping styles and to determine the individual capacity for adaptation during chronic stress exposure. Under chronic social stress exposure, we hypothesize that changes in the ENKergic vs DYNergic neuronal systems within specific nuclei of the basal forebrain contribute to naturally occurring variations in coping styles and will determine individual capacities for stress adaptation. Sprague-Dawley rats were exposed to a resident-intruder model of defeat for 7 days. The average latency to be defeated over seven consecutive days was calculated for each intruder rat. Based on this distribution, we chose an average defeat latency of 350 sec as a cutoff criterion to define resilient and vulnerable rats. A subpopulation assumed a subordinate posture in a relatively short latency (<350 sec, SL) and the other subpopulation resisted defeat resulting in longer latencies (>350 sec, LL) to assume this posture and were identified as being vulnerable and resilient respectively. Rats were euthanized 24 h after the last stress session. ENK mRNA expression was lower in the basolateral nucleus of the amygdala in vulnerable compared to control and resilient individuals. In contrast, there was no difference between resilient and control individuals. DYN mRNA is increased only within the dorsal and medial shell of the NAc of vulnerable rats compared to control individuals. There was no difference between resilient and control individuals. DYN mRNA is increased in resilient individuals in the central area of the striatum, caudal part, compared to control individuals. DYN is also increased in medial area of the striatum, caudal part in resilient and vulnerable compared to control individuals. These results have broad implications for understanding the functional roles of opioid neurotransmission following repeated social stress and suggest that ENK could facilitate the adaptation of behavioral responses by opposition to the DYN neurotransmission that appears to promote maladaptive behavioral response to chronic social stress.
  Physiology & Behavior 05/2013;
• Article: Introduction to the 2012 SSIB Special Issue.

  Nori Geary, Gary J Schwartz
  Physiology & Behavior 05/2013;
• Article: Multiple effects of circadian dysfunction induced by photoperiod shifts: Alterations in context memory and food metabolism in the same subjects.

  Robert J McDonald, Erin L Zelinski, Robin J Keeley, Dylan Sutherland, Leah Fehr, Nancy S Hong
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  ABSTRACT: Humans exposed to shiftwork conditions have been reported to have increased susceptibility to various health problems including various forms of dementia, cancer, heart disease, and metabolic disorders related to obesity. The present experiments assessed the effects of circadian disruption on learning and memory function and various food related processes including diet consumption rates, food metabolism, and changes in body weight. These experiments utilized a novel variant of the conditioned place preference task (CPP) that is normally used to assess Pavlovian associative learning and memory processes produced via repeated context-reward pairings. For the present experiments, the standard CPP paradigm was modified in that both contexts were paired with food, but the dietary constituents of the food were different. In particular, we were interested in whether rats could differentiate between two types of carbohydrates, simple (dextrose) and complex (starch). Consumption rates for each type of carbohydrate were measured throughout training. A test of context preference without the food present was also conducted. At the end of behavioural testing, a fasting glucose test and a glucose challenge test were administered. Chronic photoperiod shifting resulted in context learning and memory processes thought to be mediated by a neural circuit centered on the hippocampus. The results also showed that preferences for the different carbohydrate diets was altered in rats experiencing photoperiod shifting in that they maintained an initial preference for the simple carbohydrate throughout training. Lastly, photoperiod shifting resulted in changes in fasting blood glucose levels and elicited weight gain. These results show that chronic photoperiod shifting, which likely resulted in circadian dysfunction, impairs multiple functions of the brain and/or body in the same individual.
  Physiology & Behavior 05/2013;
• Article: Melatonin reduces body weight gain and increases nocturnal activity in male Wistar rats.

  M P Terrón, J Delgado-Adámez, J A Pariente, C Barriga, S D Paredes, A B Rodríguez
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  ABSTRACT: AIM: This study evaluated the effect of the administration of melatonin, the chief secretory product of the pineal gland, on the body weight in male Wistar rats. MAIN METHODS: The animals were housed for 4 months in cages equipped to log horizontal activity within a thermostatically-controlled chamber, under a 12h/12h light/dark photoperiod (lights on at 08:00 h). After acclimatization, the animals were divided into two groups: (1) control animals, and (2) melatonin-treated animals. Melatonin was administered in tap water (20 μg/ml), and fresh drinking fluid was changed twice weekly. Rats were fed a standard diet ad libitum. KEY FINDINGS: Food and water intake, body weight, the amplitude of the activity/rest rhythm (motor activity), and blood melatonin and glucose concentrations were measured. The administration of melatonin did not influence either food or water intake or glucose levels relative to those found in the control animals. However, melatonin administration reduced body weight gain and increased nocturnal locomotor activity. The peak concentration of melatonin was found at night coinciding with the increase in nocturnal activity. SIGNIFICANCE: The results show that exogenous melatonin reduces body weight gain without having marked effects on metabolism. This may be due in part to the increased nocturnal activity shown by the animals treated with the indoleamine.
  Physiology & Behavior 05/2013;
• Article: Manganese-enhanced magnetic resonance imaging (MEMRI) reveals brain circuitry involved in responding to an acute novel stress in rats with a history of repeated social stress.

  Debra A Bangasser, Catherine S Lee, Philip A Cook, James C Gee, Seema Bhatnagar, Rita J Valentino
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  ABSTRACT: Responses to acute stressors are determined in part by stress history. For example, a history of chronic stress results in facilitated responses to a novel stressor and this facilitation is considered to be adaptive. We previously demonstrated that repeated exposure of rats to the resident-intruder model of social stress results in the emergence of two subpopulations that are characterized by different coping responses to stress. The submissive subpopulation failed to show facilitation to a novel stressor and developed a passive strategy in the Porsolt forced swim test. Because a passive stress coping response has been implicated in the propensity to develop certain psychiatric disorders, understanding the unique circuitry engaged by exposure to a novel stressor in these subpopulations would advance our understanding of the etiology of stress-related pathology. An ex vivo functional imaging technique, manganese-enhanced magnetic resonance imaging (MEMRI), was used to identify and distinguish brain regions that are differentially activated by an acute swim stress (15 min) in rats with a history of social stress compared to controls. Specifically, Mn(2+) was administered intracerebroventricularly prior to swim stress and brains were later imaged ex vivo to reveal activated structures. When compared to controls, all rats with a history of social stress showed greater activation in specific striatal, hippocampal, hypothalamic, and midbrain regions. The submissive subpopulation of rats was further distinguished by significantly greater activation in amygdala, bed nucleus of the stria terminalis, and septum, suggesting that these regions may form a circuit mediating responses to novel stress in individuals that adopt passive coping strategies. The finding that different circuits are engaged by a novel stressor in the two subpopulations of rats exposed to social stress implicates a role for these circuits in determining individual strategies for responding to stressors. Finally, these data underscore the utility of ex vivo MEMRI to identify and distinguish circuits engaged in behavioral responses.
  Physiology & Behavior 05/2013;
• Article: Sleep duration, sleep quality and body weight: parallel developments.

  Hanne K J Gonnissen, Tanja C Adam, Rick Hursel, Femke Rutters, Sanne P M Verhoef, Margriet S Westerterp-Plantenga
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  ABSTRACT: The increase in obesity, including childhood obesity, has developed over the same time period as the progressive decrease in self-reported sleep duration. Since epidemiological studies showed an inverse relationship between short or disturbed sleep and obesity, the question arose, how sleep duration and sleep quality are associated with the development of obesity. In this review, the current literature on these topics has been evaluated. During puberty, changes in BMI are inversely correlated to changes in sleep duration. During adulthood, this relationship remains and at the same time unfavorable metabolic and neuro-endocrinological changes develop, that promote a positive energy balance, coinciding with sleep disturbance. Furthermore, during excessive weight loss BMI and fat mass decrease, in parallel, and related with an increase in sleep duration. In order to shed light on the association between sleep duration, sleep quality and obesity, until now it only has been shown that diet-induced body-weight loss and successive body-weight maintenance contribute to sleep improvement. It remains to be demonstrated whether body-weight management and body composition improve during an intervention concomitantly with spontaneous sleep improvement compared with the same intervention without spontaneous sleep improvement.
  Physiology & Behavior 05/2013;
• Article: Male Isolation: A Behavioral Representation of the Pheromonal 'Female Effect' in Donkey (Equus asinus).

  Augusto Carluccio, Alberto Contri, Sonia Amendola, Elisabetta De Angelis, Ippolito De Amicis, Andrea Mazzatenta
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  ABSTRACT: The appearance of a decisive component of the sexual response to chemosexual signals in the male donkey was investigated through a comparison of the variations in the time-span of the behavioral classes and units for the natural versus induced breeding seasons. The results demonstrate that there are significant variations in the length of the appetitive sexual behavior (ASB) and consummatory sexual behavior (CSB) under these two reproductive conditions. These differences are analyzed for the ASB, which is adaptable, compared with the stereotyped CSB. For the ASB, male isolation is the most represented behavior of both the natural and induced breeding seasons. This is the key that allows the passage from courtship, which consist of appetitive behaviors, to copula, the consummatory behavior. This isolation appears to provide the time required to activate the hypothalamic-pituitary-gonadal axis through the chemosexual pathway of pheromone stimuli. This isolation is lengthened with induced breeding, supporting the hypothesis of the activation of the neuroendocrine system, which is not 'primed' outside the natural breeding season, and which is necessary to release the stereotyped CSB.
  Physiology & Behavior 05/2013;
• Article: A test of maternal programming of offspring stress response to predation risk in threespine sticklebacks.

  Brett C Mommer, Alison M Bell
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  ABSTRACT: Non-genetic maternal effects are widespread across taxa and challenge our traditional understanding of inheritance. Maternal experience with predators, for example, can have lifelong consequences for offspring traits, including fitness. Previous work in threespine sticklebacks showed that females exposed to simulated predation risk produced eggs with higher cortisol content and offspring with altered anti-predator behavior. However, it is unknown whether this maternal effect is mediated via the offspring glucocorticoid stress response and if it is retained over the entire lifetime of offspring. Therefore, we tested the hypothesis that maternal exposure to simulated predation risk has long-lasting effects on the cortisol response to simulated predation risk in stickleback offspring. We measured circulating concentrations of cortisol before (baseline), 15 minutes after, and 60 minutes after exposure to a simulated predation risk. We compared adult offspring of predator-exposed mothers and control mothers in two different social environments (alone or in a group). Relative to baseline, offspring plasma cortisol was highest 15 minutes after exposure to simulated predation risk and decreased after 60 minutes. Offspring of predator-exposed mothers differed in the cortisol response to simulated predation risk compared to offspring of control mothers. In general, females had higher cortisol than males, and fish in a group had lower cortisol than fish that were by themselves. The buffering effect of the social environment did not differ between maternal treatments or between males and females. Altogether the results show that while a mother's experience with simulated predation risk might affect the physiological response of her adult offspring to a predator, sex and social isolation have much larger effects on the stress response to predation risk in sticklebacks.
  Physiology & Behavior 04/2013;
• Article: Role of Central Glucagon-like Peptide-1 in Stress Regulation.

  Sriparna Ghosal, Brent Myers, James P Herman
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  ABSTRACT: Glucagon-like peptide 1 (GLP-1) is best known as an incretin hormone, secreted from L cells in the intestine in response to nutrient ingestion to stimulate glucose-dependent insulin secretion. However, GLP-1 is also expressed in neurons, and plays a major role in regulation of homeostatic function within the central nervous system (CNS). This review summarizes our current state of knowledge on the role GLP-1 plays in neural coordination of the organismal stress response. In brain, the primary locus of GLP-1 production is in the caudal nucleus of the solitary tract (NTS) and the ventrolateral medulla of the hindbrain. GLP-1 immunoreactive fibers directly innervate hypophysiotrophic corticotropin-releasing hormone (CRH) neurons in the hypothalamic paraventricular nucleus (PVN), placing GLP-1 in prime position to integrate hypothalamo-pituitary-adrenocortical responses. Exogenous central GLP-1 activates HPA axis stress responses, and responses to a variety of stressors can be blocked by a GLP-1 receptor (GLP-1R) antagonist, confirming an excitatory role in glucocorticoid secretion. In addition, central infusion of GLP-1R agonist increases heart rate and blood pressure, and activates hypothalamic and brainstem neurons innervating sympathetic preganglionic neurons, suggesting a sympathoexcitatory role of GLP-1 in the CNS. Bioavailability of preproglucagon (PPG) mRNA and GLP-1 peptide is reduced by exogenous or endogenous glucocorticoid secretion, perhaps as a mechanism to reduce GLP-1-mediated stress excitation. Altogether, the data suggest that GLP-1 plays a key role in activation of stress responses, which may be connected with its role in central regulation of energy homeostasis.
  Physiology & Behavior 04/2013;
• Article: Effects of Pretraining and Water Temperature on Female Rats' Performance in the Morris Water Maze.

  E M Anderson, M D Moenk, L Barbaro, D A Clarke, L Matuszewich
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  ABSTRACT: The water maze is a complex spatial task that requires the coordination of multiple systems to perform efficiently. Various factors have been shown to influence performance in this task, including motivational state and prior experience. Although a consistent sex difference has been observed in acquiring the water maze in rats, the contribution of the various factors in female rat performance has not been fully assessed. Therefore, the current study tested the effects of motivation as manipulated by water temperature of the maze and prior experience in the maze on the performance of female rats. It was hypothesized that females pretrained in the maze would perform better than those without exposure to the water maze, regardless of water temperature, but in naïve rats, colder water would improve performance as shown previously in male rats. For pretraining, female rats were taught to find a visible platform in cold (19°C, 4 trials on one day) and warm (25°C, 4 trials on one day) water before acquisition trials, with the order of the water temperature randomly assigned. Control rats were not given any training and were naïve to the water maze procedure. Pretrained and control rats were then tested to locate a hidden platform in either cold or warm water for 5 consecutive days. Overall, pretraining had a significant effect on distance, latency, and directness of path to the platform. Water temperature did not show a significant effect on any measure or a significant interaction with pretraining. Thus, while our hypothesis that pretraining would improve performance was supported, the results did not support the prediction that water temperature would also significantly influence performance. These results show that non-spatial pretraining can critically improve the performance of females in acquiring a place strategy for the hidden platform, irrespective of water temperature.
  Physiology & Behavior 04/2013;
• Article: Sex Differences and Chronic Stress Effects on the Neural Circuitry Underlying Fear Conditioning and Extinction.

  Mollee R Farrell, Dale R Sengelaub, Cara L Wellman
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  ABSTRACT: There are sex differences in the rates of many stress-sensitive psychological disorders such as post traumatic stress disorder (PTSD). As medial prefrontal cortex and amygdala are implicated in many of these disorders, understanding differential stress effects in these regions may shed light on the mechanisms underlying sex-dependent expression of disorders like depression and anxiety. Prefrontal cortex and amygdala are key regions in the neural circuitry underlying fear conditioning and extinction, which thus has emerged as a useful model of stress influences on the neural circuitry underlying regulation of emotional behavior. This review outlines the current literature on sex differences and stress effects on dendritic morphology within medial prefrontal cortex and basolateral amygdala. Such structural differences and/or alterations can have important effects on fear conditioning and extinction, behaviors that are mediated by the basolateral amygdala and prefrontal cortex, respectively. Given the importance of extinction-based exposure therapy as a treatment for anxiety disorders such as PTSD, understanding the neural mechanisms by which stress differentially influences fear learning and extinction in males and females is an important goal for developing sex-appropriate interventions for stress-related disorders.
  Physiology & Behavior 04/2013;
• Article: An unexpected increase in restraint duration alters the expression of stress response habituation.

  Rachael R Kearns, Robert L Spencer
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  ABSTRACT: While habituation develops to a repeated psychological stressor, manipulating certain parameters of the stress challenge experience may lead to dishabituation of the stress response. In this experiment, we investigated whether the behavioral, endocrine, and neural responses (c-fos mRNA immediate early gene expression) to a psychological stressor (restraint) differ when the duration of the stressor given on the test day violates expectations based on prior stress experience. Rats experienced 10 min of daily restraint on Days 1-4 followed by challenge with either the same duration (10 min) or a longer duration (30 min) of restraint on Day 5. Rats' behavior was video recorded during the Day 5 restraint episode, and trunk blood and brain tissue were collected 30 min following restraint onset. Struggling behavior was manually scored as active attempts to escape the restraint device. Rats who experienced the same duration of repeated restraint showed a significant decrease of plasma corticosterone (CORT) compared to the 10 min acute restraint group (habituation). In addition, these rats showed decreased active struggling over repeated restraint trials. Conversely, the rats showed an increased CORT response (dishabituation) when they experienced a longer duration of restraint on Day 5 than they had previously. These rats showed a habituated behavioral response during the first 10 min of restraint, however struggling behavior increased once the duration of restraint exceeded the expected duration (with a peak at 12 min). This peak in struggling behavior did not occur during 30 min acute restraint, indicating that the effect was related to memory of previous restraint experience and not due to a longer duration of restraint. In contrast, these animals showed habituated c-fos mRNA expression in the paraventricular nucleus (PVN), lateral septum (LS), and medial prefrontal cortex (mPFC) in response to the increased stressor duration. Thus, there was dissociation between c-fos mRNA expression in key stress responsive brain regions and the behavioral and endocrine response to increased stressor duration. This dissociation may have been due to a greater lag time for c-fos mRNA responses to reflect the impact of a dishabituation response. In conclusion, habituation of the endocrine and behavioral stress response occurred when the duration of the stressor matches previous experience, while dishabituation of the stress response was triggered (with remarkable temporal precision) by an unexpected increase in stress duration.
  Physiology & Behavior 04/2013;
• Article: Dorsomedial hypothalamic NPY modulation of adiposity and thermogenesis.

  Sheng Bi
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  ABSTRACT: In addition to controlling food intake, the dorsomedial hypothalamus (DMH) plays an important role in thermoregulation. Within the DMH, a number of neuropeptides and receptors have been found and their roles in controlling energy balance are being investigated. We recently found that the orexigenic neuropeptide Y (NPY) in the DMH has specific actions on body adiposity and thermogenesis using a viral-mediated manipulation of NPY in the DMH. Knockdown of NPY in the DMH promotes the development of brown adipocytes in white adipose tissue and increases brown adipocyte activity. DMH NPY knockdown also causes increased thermogenesis and energy expenditure. Finally, DMH NPY knockdown prevents high-fat diet-induced obesity and improves glucose homeostasis. This review focuses on the role of DMH NPY in modulating body adiposity and thermogenesis.
  Physiology & Behavior 04/2013;
• Article: Acute peripheral GLP-1 Receptor Agonism or Antagonism does not alter Energy Expenditure in Rats after Roux-en-Y Gastric Bypass.

  Kathrin Abegg, Marc Schiesser, Thomas A Lutz, Marco Bueter
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  ABSTRACT: Compared to traditional weight loss strategies, the compensatory decrease in energy expenditure in response to body weight loss is markedly attenuated after Roux-en-Y gastric bypass surgery (RYGB). Because basal and postprandial levels of glucagon-like peptide-1 (GLP-1) are increased after RYGB surgery, and because GLP-1 has been shown to increase energy expenditure, we investigated if increased GLP-1 levels are involved in the alterations in energy expenditure after RYGB. Adult male Wistar rats were randomized for RYGB (n=8) or sham surgery (n=17). Part of the shamoperated rats were food restricted and body weight-matched (n=8) to the RYGB animals. The effects of acute subcutaneous administration of the GLP-1 antagonist Exendin (9-39) (Ex-9, 30μg/kg) or the GLP-1 agonist Exendin-4 (Ex-4, 5μg/kg), respectively, on energy expenditure were tested using indirect calorimetry. We found that Ex-9 increased food intake in RYGB, but not in sham-operated rats. Energy expenditure was lower in RYGB and sham-operated body weight-matched rats compared to sham-operated ad libitum fed rats, but significantly higher in RYGB rats compared to sham-operated body weight-matched rats. There was no effect of Ex-9 treatment on energy expenditure in either group of animals. Similarly, Ex-4 decreased food intake more in RYGB than in sham-operated rats, but Ex-4 did not modulate energy expenditure in any surgical group. We conclude that acute modulation of GLP-1 signaling is not directly involved in altered energy expenditure after RYGB surgery in rats.
  Physiology & Behavior 04/2013;
• Article: Brown adipose tissue thermogenesis, the basic rest-activity cycle, meal initiation, and bodily homeostasis in rats.

  William Blessing, Mazher Mohammed, Youichirou Ootsuka
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  ABSTRACT: Laboratory rats alternate between behaviorally active and inactive states every 1-2hours throughout the 24hourday, the ultradian basic rest-activity cycle (BRAC). During the behaviorally active phases of the BRAC, brown adipose tissue (BAT) temperature, body and brain temperature, and arterial pressure and heart rate increase in an integrated manner. Since the BAT temperature increases are substantially greater than the corresponding body and brain temperature increases, BAT thermogenesis contributes to the body and brain temperature increases. When food is available ad libitum, eating commences approximately 15min after the onset of an episodic increase in BAT temperature, and not at other times. If no food is available, the rat still disturbs the empty food container approximately 15min after the onset of an episodic increase in BAT temperature, and not at other times. The increase in brain temperature that precedes eating may facilitate the cognitive processing that occurs during the search for food, when the rat engages with the external environment. Rather than being triggered by changes in levels of body fuels or other meal-associated factors, in sedentary laboratory rats with ad libitum access to food, meal initiation normally occurs as part of the centrally-programmed ultradian BRAC. BRAC-associated BAT temperature increases occur in a thermoneutral environment and they are not preceded by falls in body or brain temperature, so they are not homeostatic thermoregulatory responses. The pattern of integrated behaviors and physiological functions associated with the BRAC presumably reflects Darwinian natural selection, and homeostatic thermoregulatory explanations of the BRAC-associated changes in temperature should be considered in this context.
  Physiology & Behavior 04/2013;
• Article: Lateral hypothalamus as a sensor-regulator in respiratory and metabolic control.

  Denis Burdakov, Mahesh M Karnani, Antonio Gonzalez
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  ABSTRACT: Physiological fluctuations in the levels of hormones, nutrients, and gasses are sensed in parallel by interacting control systems distributed throughout the brain and body. We discuss the logic of this arrangement and the definitions of "sensing"; and then focus on lateral hypothalamic (LH) control of energy balance and respiration. LH neurons control diverse behavioural and autonomic processes by projecting throughout the neuraxis. Three recently characterized types of LH cells are discussed here. LH orexin/hypocretin (ORX) neurons fire predominantly during wakefulness and are thought to promote reward-seeking, arousal, obesity resistance, and adaptive thermogenesis. Bidirectional control of ORX cells by extracellular macronutrients may add a new regulatory loop to these processes. ORX neurons also stimulate breathing and are activated by acid/CO2in vivo and in vitro. LH melanin-concentrating hormone (MCH) neurons fire mostly during sleep, promote physical inactivity, weight gain, and may impair glucose tolerance. Reported stimulation of MCH neurons by glucose may thus modulate energy homeostasis. Leptin receptor (LepR) neurons of the LH are distinct from ORX and MCH neurons, and may suppress feeding and locomotion by signaling to the mesolimbic dopamine system and local ORX neurons. Integration within the ORX-MCH-LepR microcircuit is suggested by anatomical and behavioural data, but requires clarification with direct assays of functional connectivity. Further studies of how LH circuits counteract evolutionarily-relevant environmental fluctuations will provide key information about the logic and fragilities of brain controllers of healthy homeostasis.
  Physiology & Behavior 04/2013;