A hypercaloric load induces thermogenesis but inhibits stress responses in the SNS and HPA system

Dietary Manipulations That Induce Ketosis Activate the HPA Axis in Male Rats and Mice: A Potential Role for Fibroblast Growth Factor-21

In response to an acute threat to homeostasis or well-being, the hypothalamic-pituitary-adrenocortical (HPA) axis is engaged. A major outcome of this HPA axis activation is the mobilization of stored energy, to fuel an appropriate behavioral and/or physiological response to the perceived threat. Importantly, the extent of HPA axis activity is thought to be modulated by an individual's nutritional environment. In this study, we report that nutritional manipulations signaling a relative depletion of dietary carbohydrates, thereby inducing nutritional ketosis, acutely and chronically activate the HPA axis. Male rats and mice maintained on a low-carbohydrate high-fat ketogenic diet (KD) exhibited canonical markers of chronic stress, including increased basal and stress-evoked plasma corticosterone, increased adrenal sensitivity to adrenocorticotropin hormone, increased stress-evoked c-Fos immunolabeling in the paraventricular nucleus of the hypothalamus, and thymic atrophy, an indicator of chronic glucocorticoid exposure. Moreover, acutely feeding medium-chain triglycerides (MCTs) to rapidly induce ketosis among chow-fed male rats and mice also acutely increased HPA axis activity. Lastly, and consistent with a growing literature that characterizes the hepatokine fibroblast growth factor-21 (FGF21) as both a marker of the ketotic state and as a key metabolic stress hormone, the HPA response to both KD and MCTs was significantly blunted among mice lacking FGF21. We conclude that dietary manipulations that induce ketosis lead to increased HPA axis tone, and that the hepatokine FGF21 may play an important role to facilitate this effect.

Sucrose-induced plasticity in the basolateral amygdala in a 'comfort' feeding paradigm

A history of intermittent, limited sucrose intake (LSI) attenuates the hypothalamic-pituitary-adrenocortical (HPA) axis stress response, and neuronal activity in the basolateral amygdala (BLA) is necessary for this HPA-dampening. LSI increases the expression of plasticity-associated genes in the BLA; however, the nature of this plasticity is unknown. As BLA principal neuron activity normally promotes HPA responses, the present study tests the hypothesis that LSI decreases stress-excitatory BLA output by decreasing glutamatergic and/or increasing GABAergic inputs to BLA principal neurons. Male rats with unlimited access to chow and water were given additional access to 4 ml of sucrose (30%) or water twice daily for 14 days, and BLA structural and functional plasticity was assessed by quantitative dual immunolabeling and whole-cell recordings in brain slices. LSI increased vesicular glutamate transporter 1-positive (glutamatergic) appositions onto parvalbumin-positive inhibitory interneurons, and this was accompanied by increased expression of pCREB, a marker of neuronal activation that is mechanistically linked with plasticity, within parvalbumin interneurons. LSI also increased the paired-pulse facilitation of excitatory, but not inhibitory synaptic inputs to BLA principal neurons, without affecting postsynaptic excitatory or miniature excitatory and inhibitory postsynaptic currents, suggesting a targeted decrease in the probability of evoked synaptic excitation onto these neurons. Collectively, these results suggest that LSI decreases BLA principal neuron output by increasing the excitatory drive to parvalbumin inhibitory interneurons, and decreasing the probability of evoked presynaptic glutamate release onto principal neurons. Our data further imply that palatable food consumption blunts HPA stress responses by decreasing the excitation-inhibition balance and attenuating BLA output.

Statistical modeling implicates neuroanatomical circuit mediating stress relief by 'comfort' food

A history of eating highly palatable foods reduces physiological and emotional responses to stress. For instance, we have previously shown that limited sucrose intake (4 ml of 30 % sucrose twice daily for 14 days) reduces hypothalamic-pituitary-adrenocortical (HPA) axis responses to stress. However, the neural mechanisms underlying stress relief by such 'comfort' foods are unclear, and could reveal an endogenous brain pathway for stress mitigation. As such, the present work assessed the expression of several proteins related to neuronal activation and/or plasticity in multiple stress- and reward-regulatory brain regions of rats after limited sucrose (vs. water control) intake. These data were then subjected to a series of statistical analyses, including Bayesian modeling, to identify the most likely neurocircuit mediating stress relief by sucrose. The analyses suggest that sucrose reduces HPA activation by dampening an excitatory basolateral amygdala-medial amygdala circuit, while also potentiating an inhibitory bed nucleus of the stria terminalis principle subdivision-mediated circuit, resulting in reduced HPA activation after stress. Collectively, the results support the hypothesis that sucrose limits stress responses via plastic changes to the structure and function of stress-regulatory neural circuits. The work also illustrates that advanced statistical methods are useful approaches to identify potentially novel and important underlying relationships in biological datasets.

Self-medication with sucrose

For many individuals, stress promotes the consumption of sweet, high-sugar foods relative to healthier alternatives. Daily life stressors stimulate the overeating of highly-palatable foods through multiple mechanisms, including altered glucocorticoid, relaxin-3, ghrelin and serotonin signaling in brain. In turn, a history of consuming high-sugar foods attenuates the psychological (anxiety and depressed mood) and physiological (HPA axis) effects of stress. Together the metabolic and hedonic properties of sucrose contribute to its stress relief, possibly via actions in both the periphery (e.g., glucocorticoid receptor signaling in adipose tissue) and in the brain (e.g., plasticity in brain reward regions). Emerging work continues to reveal the bidirectional mechanisms that underlie the use of high-sugar foods as 'self-medication' for stress relief.

Interacting Neural Processes of Feeding, Hyperactivity, Stress, Reward, and the Utility of the Activity-Based Anorexia Model of Anorexia Nervosa

Anorexia nervosa (AN) is a psychiatric illness with minimal effective treatments and a very high rate of mortality. Understanding the neurobiological underpinnings of the disease is imperative for improving outcomes and can be aided by the study of animal models. The activity-based anorexia rodent model (ABA) is the current best parallel for the study of AN. This review describes the basic neurobiology of feeding and hyperactivity seen in both ABA and AN, and compiles the research on the role that stress-response and reward pathways play in modulating the homeostatic drive to eat and to expend energy, which become dysfunctional in ABA and AN.

Central nervous system regulation of brown adipose tissue

Thermogenesis, the production of heat energy, in brown adipose tissue is a significant component of the homeostatic repertoire to maintain body temperature during the challenge of low environmental temperature in many species from mouse to man and plays a key role in elevating body temperature during the febrile response to infection. The sympathetic neural outflow determining brown adipose tissue (BAT) thermogenesis is regulated by neural networks in the CNS which increase BAT sympathetic nerve activity in response to cutaneous and deep body thermoreceptor signals. Many behavioral states, including wakefulness, immunologic responses, and stress, are characterized by elevations in core body temperature to which central command-driven BAT activation makes a significant contribution. Since energy consumption during BAT thermogenesis involves oxidation of lipid and glucose fuel molecules, the CNS network driving cold-defensive and behavioral state-related BAT activation is strongly influenced by signals reflecting the short- and long-term availability of the fuel molecules essential for BAT metabolism and, in turn, the regulation of BAT thermogenesis in response to metabolic signals can contribute to energy balance, regulation of body adipose stores and glucose utilization. This review summarizes our understanding of the functional organization and neurochemical influences within the CNS networks that modulate the level of BAT sympathetic nerve activity to produce the thermoregulatory and metabolic alterations in BAT thermogenesis and BAT energy expenditure that contribute to overall energy homeostasis and the autonomic support of behavior.

Stress exposure, food intake and emotional state

This manuscript summarizes the proceedings of the symposium entitled, "Stress, Palatable Food and Reward", that was chaired by Drs. Linda Rinaman and Yvonne Ulrich-Lai at the 2014 Neurobiology of Stress Workshop held in Cincinnati, OH. This symposium comprised research presentations by four neuroscientists whose work focuses on the biological bases for complex interactions among stress, food intake and emotion. First, Dr Ulrich-Lai describes her rodent research exploring mechanisms by which the rewarding properties of sweet palatable foods confer stress relief. Second, Dr Stephanie Fulton discusses her work in which excessive, long-term intake of dietary lipids, as well as their subsequent withdrawal, promotes stress-related outcomes in mice. Third, Dr Mark Wilson describes his group's research examining the effects of social hierarchy-related stress on food intake and diet choice in group-housed female rhesus macaques, and compared the data from monkeys to results obtained in analogous work using rodents. Finally, Dr Gorica Petrovich discusses her research program that is aimed at defining cortical-amygdalar-hypothalamic circuitry responsible for curbing food intake during emotional threat (i.e. fear anticipation) in rats. Their collective results reveal the complexity of physiological and behavioral interactions that link stress, food intake and emotional state, and suggest new avenues of research to probe the impact of genetic, metabolic, social, experiential and environmental factors on these interactions.

Neuroendocrine circuits governing energy balance and stress regulation: functional overlap and therapeutic implications

Significant comorbidities between obesity-related metabolic disease and stress-related psychological disorders suggest important functional interactions between energy balance and brain stress integration. Largely overlapping neural circuits control these systems, and this anatomical arrangement optimizes opportunities for mutual influence. Here we first review the current literature identifying effects of metabolic neuroendocrine signals on stress regulation, and vice versa. Next, the contributions of reward-driven food intake to these metabolic and stress interactions are discussed. Lastly, we consider the interrelationships between metabolism, stress, and reward in light of their important implications in the development of therapies for metabolism- or stress-related disease.

Protracted effects of juvenile stressor exposure are mitigated by access to palatable food

Stressor experiences during the juvenile period may increase vulnerability to anxiety and depressive-like symptoms in adulthood. Stressors may also promote palatable feeding, possibly reflecting a form of self-medication. The current study investigated the short- and long-term consequences of a stressor applied during the juvenile period on anxiety- and depressive-like behavior measured by the elevated plus maze (EPM), social interaction and forced swim test (FST). Furthermore, the effects of stress on caloric intake, preference for a palatable food and indices of metabolic syndrome and obesity were assessed. Male Wistar rats exposed to 3 consecutive days of variable stressors on postnatal days (PD) 27–29, displayed elevated anxiety-like behaviors as adults, which could be attenuated by consumption of a palatable high-fat diet. However, consumption of a palatable food in response to a stressor appeared to contribute to increased adiposity.

Leptin and the hypothalamo-pituitary-adrenal stress axis

Leptin is a 16-kDa protein mainly produced and secreted by white adipose tissue and informing various brain centers via leptin receptor long and short forms about the amount of fat stored in the body. In this way leptin exerts a plethora of regulatory functions especially related to energy intake and metabolism, one of which is controlling the activity of the hypothalamo-pituitary-adrenal (HPA) stress axis. First, this review deals with the basic properties of leptin's structure and signaling at the organ, cell and molecule level, from lower vertebrates to humans but with emphasis on rodents because these have been investigated in most detail. Then, attention is given to the various interactions of adipose leptin with the HPA-axis, at the levels of the hypothalamus (especially the paraventricular nucleus), the anterior lobe of the pituitary gland (action on corticotropes) and the adrenal gland, where it releases corticosteroids needed for adequate stress adaptation. Also, possible local production and autocrine and paracrine actions of leptin at the hypothalamic and pituitary levels of the HPA-axis are being considered. Finally, a schematic model is presented showing the ways peripherally and centrally produced leptin may modulate, via the HPA-axis, stress adaptation in conjunction with the control of energy homeostasis.

Changes in glucose tolerance and leptin responsiveness of rats offered a choice of lard, sucrose, and chow

Rats offered chow, lard, and 30% sucrose solution (choice) rapidly become obese. We tested metabolic disturbances in rats offered choice, chow+lard, or chow+30% sucrose solution [chow+liquid sucrose (LS)] and compared them with rats fed a composite 60% kcal fat, 7% sucrose diet [high-fat diet (HFD)], or a 10% kcal fat, 35% sucrose diet [low-fat diet (LFD)]. Choice rats had the highest energy intake, but HFD rats gained the most weight. After 23 days carcass fat was the same for choice, HFD, chow+lard, and chow+LS groups. Glucose clearance was the same for all groups during an intraperitoneal glucose tolerance test (GTT) on day 12, but fasting insulin was increased in choice, LFD fed, and chow+LS rats. By contrast, only choice and chow+LS rats were resistant to an intraperitoneal injection of 2 mg leptin/kg on day 17. In experiment 2 choice rats were insulin insensitive during an intraperitoneal GTT, but this was corrected in an oral GTT due to GLP-1 release. UCP-1 protein was increased in brown fat and inguinal white fat in choice rats, and this was associated with a significant increase in energy expenditure of choice rats during the dark period whether expenditure was expressed on a per animal or a metabolic body size basis. The increase in expenditure obviously was not great enough to prevent development of obesity. Further studies are required to determine the mechanistic basis of the rapid onset of leptin resistance in choice rats and how consumption of sucrose solution drives this process.

Regulatory interactions of stress and reward on rat forebrain opioidergic and GABAergic circuitry

Palatable food intake reduces stress responses, suggesting that individuals may consume such ?comfort? food as self-medication for stress relief. The mechanism by which palatable foods provide stress relief is not known, but likely lies at the intersection of forebrain reward and stress regulatory circuits. Forebrain opioidergic and gamma-aminobutyric acid ergic signaling is critical for both reward and stress regulation, suggesting that these systems are prime candidates for mediating stress relief by palatable foods. Thus, the present study (1) determines how palatable ?comfort? food alters stress-induced changes in the mRNA expression of inhibitory neurotransmitters in reward and stress neurocircuitry and (2) identifies candidate brain regions that may underlie comfort food-mediated stress reduction. We used a model of palatable ?snacking? in combination with a model of chronic variable stress followed by in situ hybridization to determine forebrain levels of pro-opioid and glutamic acid decarboxylase (GAD) mRNA. The data identify regions within the extended amygdala, striatum, and hypothalamus as potential regions for mediating hypothalamic-pituitary-adrenal axis buffering following palatable snacking. Specifically, palatable snacking alone decreased pro-enkephalin-A (ENK) mRNA expression in the anterior bed nucleus of the stria terminalis (BST) and the nucleus accumbens, and decreased GAD65 mRNA in the posterior BST. Chronic stress alone increased ENK mRNA in the hypothalamus, nucleus accumbens, amygdala, and hippocampus; increased dynorphin mRNA in the nucleus accumbens; increased GAD65 mRNA in the anterior hypothalamus and BST; and decreased GAD65 mRNA in the dorsal hypothalamus. Importantly, palatable food intake prevented stress-induced gene expression changes in subregions of the hypothalamus, BST, and nucleus accumbens. Overall, these data suggest that complex interactions exist between brain reward and stress pathways and that palatable snacking can mitigate many of the neurochemical alterations induced by chronic stress.

"Snacking" causes long term attenuation of HPA axis stress responses and enhancement of brain FosB/deltaFosB expression in rats

A history of limited, intermittent intake of palatable food (sucrose drink) attenuates hypothalamic-pituitary-adrenal (HPA) axis stress responses and induces markers of neuronal plasticity in stress- and reward-regulatory brain regions. Synaptic plasticity could provide a mechanism for long-term changes in neuronal function, implying that sucrose stress-dampening may endure over long periods of time. The present study tests the persistence of HPA axis dampening and plasticity after cessation of palatable drinking. Adult, male Long-Evans rats (n=10-13) with free access to water and chow were given additional twice-daily access to 4ml sucrose (30%) or water for 14days. Rats were subsequently tested for HPA responsiveness to an acute (20min) restraint stress at 1, 6 and 21days after the cessation of sucrose. Brains were collected for immunohistochemical analysis of FosB/deltaFosB, a marker of long-term neuronal plasticity, in the basolateral amygdala (BLA) and nucleus accumbens (NuAc). Prior sucrose consumption significantly decreased the plasma corticosterone response to restraint at 1day after the last palatable drink presentation, and also increased FosB/deltaFosB-positive cells in the BLA and in the NuAc core. This HPA-dampening persisted through 21days after the termination of the palatable drink, as did the increased FosB/deltaFosB immunoreactivity in both the BLA and the NuAc core. These data suggest that chronic palatable food intake causes lasting changes in stress/reward-modulatory circuitry and that the suppressed hormonal response to stress that can persist well beyond periods of palatable drink exposure.

HPA axis dampening by limited sucrose intake: reward frequency vs. caloric consumption

Individuals often cope with stress by consuming calorically-dense, highly-palatable 'comfort' foods. The present work explores the stress-relieving properties of palatable foods in a rat model of limited sucrose intake. In this model, adult male rats with free access to chow and water are given additional access to a small amount of sucrose drink (or water as a control). A history of such limited sucrose intake reduces the collective (HPA axis, sympathetic, and behavioral-anxiety) stress response. Moreover, the stress-dampening by sucrose appears to be mediated primarily by its rewarding properties, since beneficial effects are reproduced by the noncaloric sweetener saccharin but not oral intragastric gavage of sucrose. The present work uses an alternate strategy to address the hypothesis that the rewarding properties of sucrose mediate its stress-dampening. This work varies the duration, frequency, and/or volume of sucrose and assesses the ability to attenuate HPA axis stress responses. The data indicate that HPA-dampening is optimal with a greater duration and/or frequency of sucrose, whereas increasing the volume of sucrose consumed is without effect. This finding suggests that the primary factor mediating stress-dampening is the number/rate of reward (i.e., sucrose) exposures, rather than the total sucrose calories consumed. Collectively, these data support the hypothesis that stress relief by limited palatable food intake is mediated primarily by its hedonic/rewarding properties. Moreover, the results support the contention that naturally rewarding behaviors are a physiological means to produce stress relief.

Diet choice, cortisol reactivity, and emotional feeding in socially housed rhesus monkeys

Chronic psychosocial stress produces an array of adverse health consequences that are highly comorbid, including emotional eating, affective disorders, and metabolic syndrome. The consumption of high caloric diets (HCDs) is thought to provide comfort in the face of unrelenting psychosocial stress. Using social subordination in female rhesus monkeys as a model of continual exposure to daily stressors in women, we tested the hypothesis that subordinate females would consume significantly more calories from a HCD compared to dominant females, and this pattern of food intake would be associated with reduced cortisol release and reduced frequency of anxiety-like behaviors. Food intake, parameters of cortisol secretion, and socio-emotional behavior were assessed for 3 weeks during a no choice phase when only a low caloric diet (LCD) was available and during a choice condition when both a LCD and HCD were available. While all animals preferred the HCD, subordinate females consumed significantly more of the HCD than did dominant females. A flattening of the diurnal cortisol rhythm and a greater increase in serum cortisol to an acute social separation occurred during the diet choice condition in all females. Furthermore, the rate of anxiety-like behavior progressively declined during the 3-week choice condition in subordinate but not dominant females. These data provide support for the hypothesis that daily exposure to psychosocial stress increases consumption of calorically dense foods. Furthermore, consumption of HCDs may be a metabolic stressor that synergizes with the psychosocial stress of subordination to further increase the consumption of these diets.

Intermittent access to sucrose increases sucrose-licking activity and attenuates restraint stress-induced activation of the lateral septum

Intermittent access to palatable food can attenuate anorectic and hormonal responses to stress in rats. The neuronal mechanisms of modulation of stress response by diets are not fully understood. The present study was conducted to create rat models with intermittent access to sucrose that demonstrate resistance to stress-induced hypophagia, to study the pattern of sucrose consumption by these rat models, and to investigate in which brain structures intermittent sucrose regimens modify stress-induced neuronal activation. The obtained results demonstrate that 6-wk intermittent access to sucrose without food restriction (4 day/wk ad libitum access to sucrose in addition to chow, and following 3 day/wk exclusive feeding of chow; SIA rats) and combined with food restriction (4 day/wk access to chow and sucrose restricted to 2 h/day, and following 3 days/wk on unrestricted chow; SIR rats) increased sucrose-licking activity. The alterations in the rats' feeding behavior were accompanied by a resistance of their body weight gain and food intake to 1-h restraint stress applied once per week. The chronic intermittent sucrose consumption significantly lowered, in the SIA and SIR rats, the levels of expression of corticotropin-releasing factor type 2 receptor and restraint stress-induced expression of c- fos mRNA in the medioventral part of the lateral septum. Conversely, the levels of the corticotropin-releasing factor type 2 receptor transcript in the ventromedial hypothalamic nucleus were decreased only in the food-restricted SIR rats. The lower stress-induced neuronal activation in the medioventral part of the lateral septum may contribute to the attenuated anorectic stress response in the rats maintained on intermittent sucrose regimens.

Neural regulation of endocrine and autonomic stress responses

The survival and well-being of all species requires appropriate physiological responses to environmental and homeostatic challenges. The re- establishment and maintenance of homeostasis entails the coordinated activation and control of neuroendocrine and autonomic stress systems. These collective stress responses are mediated by largely overlapping circuits in the limbic forebrain, the hypothalamus and the brainstem, so that the respective contributions of the neuroendocrine and autonomic systems are tuned in accordance with stressor modality and intensity. Limbic regions that are responsible for regulating stress responses intersect with circuits that are responsible for memory and reward, providing a means to tailor the stress response with respect to prior experience and anticipated outcomes.

Daily limited access to sweetened drink attenuates hypothalamic-pituitary-adrenocortical axis stress responses

Stress can promote palatable food intake, and consumption of palatable foods may dampen psychological and physiological responses to stress. Here we develop a rat model of daily limited sweetened drink intake to further examine the linkage between consumption of preferred foods and hypothalamic-pituitary-adrenocortical axis responses to acute and chronic stress. Adult male rats with free access to water were given additional twice-daily access to 4 ml sucrose (30%), saccharin (0.1%; a noncaloric sweetener), or water. After 14 d of training, rats readily learned to drink sucrose and saccharin solutions. Half the rats were then given chronic variable stress (CVS) for 14 d immediately after each drink exposure; the remaining rats (nonhandled controls) consumed their appropriate drinking solution at the same time. On the morning after CVS, responses to a novel restraint stress were assessed in all rats. Multiple indices of chronic stress adaptation were effectively altered by CVS. Sucrose consumption decreased the plasma corticosterone response to restraint stress in CVS rats and nonhandled controls; these reductions were less pronounced in rats drinking saccharin. Sucrose or saccharin consumption decreased CRH mRNA expression in the paraventricular nucleus of the hypothalamus. Moreover, sucrose attenuated restraint-induced c-fos mRNA expression in the basolateral amygdala, infralimbic cortex, and claustrum. These data suggest that limited consumption of sweetened drink attenuates hypothalamic-pituitary-adrenocortical axis stress responses, and calories contribute but are not necessary for this effect. Collectively the results support the hypothesis that the intake of palatable substances represents an endogenous mechanism to dampen physiological stress responses.

Stress facilitates body weight gain in genetically predisposed rats on medium-fat diet

To assess the interaction between stress and energy homeostasis, we immobilized male Sprague-Dawley rats prone to diet-induced obesity (DIO) or diet resistance (DR) once for 20 min and then fed them either low-fat (4.5%) chow or a medium-fat (31%), high-energy (HE) diet for 9 days. Stressed, chow-fed DIO rats gained less, while stressed DIO rats on HE diet gained more body weight and had higher feed efficiency and plasma leptin levels than unstressed controls. Neither stress nor diet affected DR body weight gain. While stress-induced plasma corticosterone levels did not differ between phenotypes, DIO rats were initially more active in an open field and had higher hippocampal dentate gyrus and CA1 glucocorticoid receptor (GR) mRNA than DR rats, regardless of prior stress or diet. HE diet intake was associated with raised dentate gyrus and CA1 GR and amygdalar central nucleus (CeA) corticotropin-releasing hormone (CRH) mRNA expression, while stress was associated with reduced hypothalamic dorsomedial nucleus Ob-R mRNA and CeA CRH specifically in DIO rats fed HE diet. Thus a single stress triggers a complex interaction among weight gain phenotype, diet, and stress responsivity, which determines the body weight and adiposity of a given individual.

Disruption of arcuate/paraventricular nucleus connections changes body energy balance and response to acute stress

The mediobasal hypothalamus regulates functions necessary for survival, including body energy balance and adaptation to stress. The purpose of this experiment was to determine the contribution of the arcuate nucleus (ARC) in controlling these two functions by the paraventricular nucleus (PVN). Circular, horizontal cuts (1.0 mm radius) were placed immediately above the anterior ARC to sever afferents to the PVN. In shams the knife was lowered to the same coordinates but was not rotated. Food intake and body weight were monitored twice daily, at the beginning and end of the light cycle, for 1 week. On the final day the animals were restrained for 30 min. Lesioned animals had increased food intake in light and dark periods, higher weight gain per day, and more body fat as compared with shams. There was no difference in caloric efficiency. Unlike shams, lesioned rats had no predictable relationship between plasma insulin and leptin. Plasma ACTH was increased at 0 min in lesioned rats but was decreased 15 and 30 min after restraint as compared with shams. There was no difference in plasma corticosterone. Immunostaining revealed that alpha-melanocortin (alphaMSH) and neuropeptide Y (NPY) accumulated below the cuts, and both were decreased in PVN. Food intake and body weight were correlated negatively to alphaMSH, but not NPY in PVN. There was no difference in proopiomelanocortin (POMC) mRNA, but NPY mRNA was reduced in the ARC of lesioned animals. We conclude that ARC controls body energy balance in unstressed rats, possibly by alphaMSH input to PVN, and that ARC also is necessary for PVN regulation of ACTH.