24-h Food Deprivation Research Articles

Motivating operations as contexts for operant discrimination training and testing

Two groups of mice were exposed to stimulus discrimination training and testing under different motivational conditions to study interactions between motivating operations (MOs) during initial discrimination training and MOs when performance is tested following training. One group received all discrimination training sessions under 24-h food deprivation while the other received all sessions under 0-h food deprivation. The number of responses allowed during discrimination training sessions was limited such that the two groups experienced the same number of response-outcome contingencies. The groups then received two post-discrimination training tests: one conducted under 24-h food deprivation and the other conducted under 0-h food deprivation. Results indicated no difference between groups in terms of discrimination ratio. However, subjects trained under 24-h deprivation made more responses in the 24-h test, while subjects trained under 0-h deprivation made more responses in the 0-h test. These results are discussed in terms of motivational state-dependent learning.

Short-term fasting induced changes in HRV are associated with interoceptive accuracy: Evidence from two independent within-subjects studies

Previous research suggested increased cardiac interoceptive accuracy after 24-h food-deprivation by means of the heartbeat tracking task. The present study investigated if 16-h of voluntary fasting shows similar effects and whether changes in interoceptive accuracy are accompanied by changes in autonomic function. In two independent within-subjects studies two measures of interoceptive accuracy, the heartbeat tracking task and the heartbeat discrimination task were applied. In study 1 (n = 24) and study 2 (n = 72) vagally-mediated HRV increases and heart rate decreases were observed. Stronger effects of fasting on vagally-mediated HRV went along with a higher interoceptive accuracy increase in the heartbeat tracking task. Furthermore, the fasting associated changes in interoceptive accuracy in both tasks were significantly associated, suggesting that these tasks are suitable to track changes in cardiac interoception. Taken together, fasting of 16-h might be suitable to increase participants’ parasympathetic efference, thereby facilitating interoception.

Acute stress-induced neuronal plasticity in the corticoid complex of 15-day-old chick, Gallus domesticus.

Several studies conducted on chicken have shown that a single stress exposure may impair or improve memory as well as learning processes. However, to date, stress effects on neuronal morphology are poorly investigated wherefore it was of interest to evaluate this further in chicks. Thus, the present study aims to investigate the role of single acute stress (AS) of 24h food and water deprivation in neuronal plasticity in terms of spine density of the corticoid complex (CC) in 15-day-old chick, Gallus domesticus, by using three neurohistological techniques: Cresyl Violet, Golgi Colonnier, and Golgi Cox technique. The dorsolateral surface of the cerebral hemisphere is occupied by CC which can be differentiated into two subfields: an intermediate corticoid (CI) subfield (arranged in layers) and a dorsolateral corticoid (CDL) subfield. Based on different criteria such as soma shape, dendritic branching pattern, and dendritic spine density, two main moderately spinous groups of neuronal cells were observed in the CC, namely, projection neurons (comprising of multipolar and pyramidal neurons) and stellate neurons. In the present study, the stellate neurons have shown a significant decrease as well as an increase in their spine density in both CI and CDL subfields, whereas the multipolar neurons had shown a significant increase in their spine density in the CDL region only. The present study shows that AS induces neuronal plasticity in terms of spine density in both CI and CDL neurons. The morphological changes in the form of decreased dendritic branches due to stress have been observed in the CI region in comparison to CDL region, which could be linked to more effect of stress in this region. The avian CDL corresponds to the entorhinal cortex of mammals on the basis of neuronal morphology and bidirectional connections between adjacent areas. The projection neurons increase their branches and also their spine number to cope with the stress effects, while the stellate neurons show contrasting effect in their spine density. Therefore, this study will establish that slight modifications in natural stimuli or environmental changes faced by the animal may affect their dorsolateral forebrain which shows neuronal plasticity that help in the development of an adaptive capacity of the animal to survive under changing environmental conditions.

"Behavior" of the Hormonal Ensemble through the Prism of Cluster Analysis.

The serum hormone concentrations were studied in a group of male F1 (C57BL/6×DBA/2) mice in different states of food activity (satiety, 24-h food deprivation, and cognitive load against the background of food deprivation). The hormonal response depended on food activity: the content of leptin, triiodothyronine, and testosterone decreased in hungry animals, while during cognitive load (learning), we observed a decrease in the concentrations of ghrelin, leptin, thyroxine, and testosterone. The exceptions were neuropeptide Y (its concentration increased in hungry animals) and corticosterone (its level remained unchanged). The use of hierarchical cluster analysis allowed identifying functional organization of the relationships within the hormonal ensemble that underwent plastic changes depending on the state of the organism. It was shown that the hormonal ensemble was system-organized in the form of a "core" that determines stability of the system and the "field", within which functional interactions of the hormones are preserved.

Dietary squid paste supplementation promotes feed intake via brain-gut dynamic response in Chinese soft-shelled turtle Pelodiscus sinensis.

BackgroundAs the primary source of protein for aquaculture, fishmeal has reached the extremity of sustainable development, our previous studies have proven that rice protein concentrate and squid paste are outstanding protein source and stimulant for Pelodiscus sinensis. However, little attention has been given to the molecular mechanism of the appetite modulated by the dietary nutrient factor, especially for a reptile. Thus, the present study aimed to evaluate feed intake and brain-gut dynamic responses to dietary rice protein concentrate and squid paste in Chinese soft-shelled turtle Pelodiscus sinensis.MethodsThree isonitrogenous and isoenergetic practical diets were formulated including 60% fishmeal (CT), 42% fishmeal + 18% rice protein concentrate (RP) and 42% fishmeal + 18% rice protein concentrate + 1% squid paste (RPS), respectively. Microcapsule lysine was supplemented in RP and RPS diets to balance the amino acid profile. Turtles (initial weight 30.65 ± 0.97 g) were fed three times daily to apparent satiation. After the 8-week feeding trial, the turtles were exposed to 48h food deprivation, then the dynamic expression of the orexigenic and anorexigenic peptides were measured.ResultsThe results showed that no significant effect was observed on feed intake when fishmeal was replaced by rice protein concentrate (P = 0.421), while significantly improved feed intake was found by squid paste supplemented (P = 0.02). The mRNA expression of anorexigenic peptides, such as leptin receptor, insulin receptor, pro-opiomelanocortin, cocaine and amphetamine-regulated transcript, cholecystokinin (and its receptor) and glucagon-like peptide-1 receptor in the brain increased significantly at 3 h past feeding (P < 0.05), and then decreased. Nevertheless, neuropeptide Y and peptide YY mRNA expression showed the valley at 3h and peak at 12h past feeding. Intestinal cholecystokinin receptor and glucagon-like peptide-1 receptor mRNA expression showed no difference during the postprandial time (P > 0.05). The results suggested that squid paste is an outstanding stimulant for Pelodiscus sinensis. Furthermore, the orexigenic and anorexigenic peptides evaluated here might play an essential role in short-term fasting to this species, of which the dynamic expression levels were regulated by squid paste.

To starve or not to starve: Deprivation of essential fatty acids and change in escape behavior during starvation by nauplii of the tropical calanoid copepod Pseudodiaptomus annandalei

In nature, marine organisms often face temporal and spatial patchy food sources and are therefore adapted physiologically and behaviourally to these situations. Tropical open water copepods frequently experience food deprivation, which may constrain their growth. Four distinct size fractions of nauplii of the tropical calanoid copepod Pseudodiaptomus annandalei were tested for their response to food deprivation. A 48-h food deprivation period caused a high mortality of 26–71%, a significant effect on molting and on length increments that were reduced by 27–38% compared to non-starved nauplii. Furthermore, the essential fatty acids, arachidonic acid (ARA), eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA) were reduced by >65% within the 48 h starvation period, and were most profound for the earliest development stages of nauplii. To examine the effect of starvation on the individual copepod nauplius ability to escape a potential predator, a flow generated hydrodynamic signal was used to stimulate an escape response. Starvation slowed down the average escape velocity of the nauplius by up to 49%, and significantly reduced the initial nauplii development stages ability to escape from the flow-generated suction. Additionally, the initial nauplii stages net to gross displacement ratio (NGDR) were significantly reduced by starvation. Hence, the nauplii response to overcome food deprivation is exhibited by both ‘sit and wait’ while recruiting storage compounds and by minimizing their motile behavior. Since starvation affects the nauplii stages escape performance, it is likely to have a profound effect on their ability to avoid a potential predator.

The role of the adiponectin system in acute fasting-impaired mouse ovaries.

Adiponectin (ADIPOQ, encoded by Adipoq) is an important white adipose-derived adipokine linked to energy homeostasis and reproductive function. This study aims to reveal the expression and role of the adiponectin system in the ovaries under acute malnutrition. In this study, 48-h food deprivation significantly inhibited ovarian growth by suppressing cell proliferation and inducing cell apoptosis in the ovaries of gonadotrophin-primed immature mice. It was also accompanied by significantly decelerated basic metabolism (glucose, triacylglycerol and cholesterol), varied steroid hormones (follicle-stimulating hormone, luteinizing hormone and estradiol) and vanishment of the peri-ovarian fat. It is noteworthy that after acute fasting, the adiponectin levels in ovaries rather than in blood were significantly elevated. Immunohistochemical study demonstrated that adiponectin and its receptors (ADIPOR1 and ADIPOR2) primarily appeared in ovarian somatic and/or germ cells, and their protein expressions were upregulated in the ovaries from fasted mice. Further in vitro study verified that ADIPOR1/2 agonist obviously inhibited follicle-stimulating hormone-induced oocyte meiotic resumption, while the antagonist significantly enhanced the percentage of oocyte maturation in the absence of follicle-stimulating hormone. Furthermore, the build up of peri-ovarian fat under physiological status in mice showed a positive correlation with both the hypertrophy of adipocytes and growth of ovaries. Taken together, these findings indicate that the upregulation of the adiponectin system disturbs the normal female reproductive function under the malnutrition status, and it may be associated with the loss of peri-ovarian fat depots.

Centella asiatica prevents chronic unpredictable mild stress-induced behavioral changes in rats

Background: Depression is a psychological disorder which is associated with mood swings and cognitive deficits, and is ranked third among the leading causes of global health care burden. Chronic unpredictable mild stress (CUMS) has been shown to induce depression-like behaviors in rodents, which exhibit similarities to the human form of depression. Centella asiatica (CA) is an ancient medicinal plant which has neuroprotective potential. This work aimed to assess the protective role of CA on CUMS-induced rats.&#x0D; Methods: Thirty six rats randomly divided into six groups were used for the evaluation. The groups were as follows: 1, Unstressed + normal saline (control); 2, CUMS + normal saline (model); 3, CUMS + fluoxetine (10 mg/kg) standard antidepressant; 4-6, CUMS + CA (200, 400 &amp; 800 mg/kg). Nine different stressors (S) (S1: 24-h food deprivation, S2: 24- h water deprivation, S3: 5-min cold swimming (at 5◦C), S4: 12-h change of cage mate, S5: 1-min tail pinch (1 cm from the tip of the tail), S6: 12-h cage tilt (at 45◦), S7: 12-h overcrowding of cage, S8: 12-h wet bedding with 200 mL of water, and S9: 4-h physical restraint) were administered to the stressed groups with at least 2 stressors per day. The treatments lasted for 8 weeks, and the rats were evaluated through open field test (OFT) and elevated plus maze (EPM) for anxiety-like behavior, forced swimming test (FST) for depression-like behaviour, and T-maze spontaneous alternation for learning and memory. Furthermore, serum cortisol levels were also evaluated.&#x0D; Results: CUMS-induced rats showed anxiety-like behaviors in OFT and EPM tests, depression-like behavior in FST and cognitive deficits in T-maze test, as well as increased serum cortisol levels. Conversely, administration of CA (at 400 and 800 mg/kg doses) and fluoxetine (at 10 mg/kg dose) prevented the aberrant behavioral changes and also the changes in the serum cortisol levels. No significant differences of behaviors were observed between the groups of rats administered with CA (400 and 800 mg/kg) and those administered with fluoxetine (10 mg/kg), suggesting that the therapeutic potential of CA is comparable to that of fluoxetine.&#x0D; Conclusion: The data obtained showed that CA, at doses of 400 and 800 mg/kg, effectively reversed the anxiety and depression-like behaviors, amnesic behaviors, as well as serum cortisol levels in a CUMS-induced rat model of depression. This suggests that CA is a potential candidate for the development of future anti-depressants.&#x0D;

The Diurnal Timing of Starvation Differently Impacts Murine Hepatic Gene Expression and Lipid Metabolism - A Systems Biology Analysis Using Self-Organizing Maps.

Organisms adapt their metabolism and draw on reserves as a consequence of food deprivation. The central role of the liver in starvation response is to coordinate a sufficient energy supply for the entire organism, which has frequently been investigated. However, knowledge of how circadian rhythms impact on and alter this response is scarce. Therefore, we investigated the influence of different timings of starvation on global hepatic gene expression. Mice (n = 3 each) were challenged with 24-h food deprivation started in the morning or evening, coupled with refeeding for different lengths and compared with ad libitum fed control groups. Alterations in hepatocyte gene expression were quantified using microarrays and confirmed or complemented with qPCR, especially for lowly detectable transcription factors. Analysis was performed using self-organizing maps (SOMs), which bases on clustering genes with similar expression profiles. This provides an intuitive overview of expression trends and allows easier global comparisons between complex conditions. Transcriptome analysis revealed a strong circadian-driven response to fasting based on the diurnal expression of transcription factors (e.g., Ppara, Pparg). Starvation initiated in the morning produced known metabolic adaptations in the liver; e.g., switching from glucose storage to consumption and gluconeogenesis. However, starvation initiated in the evening produced a different expression signature that was controlled by yet unknown regulatory mechanisms. For example, the expression of genes involved in gluconeogenesis decreased and fatty acid and cholesterol synthesis genes were induced. The differential regulation after morning and evening starvation were also reflected at the lipidome level. The accumulation of hepatocellular storage lipids (triacylglycerides, cholesteryl esters) was significantly higher after the initiation of starvation in the morning compared to the evening. Concerning refeeding, the gene expression pattern after a 12 h refeeding period largely resembled that of the corresponding starvation state but approached the ad libitum control state after refeeding for 21 h. Some components of these regulatory circuits are discussed. Collectively, these data illustrate a highly time-dependent starvation response in the liver and suggest that a circadian influence cannot be neglected when starvation is the focus of research or medicine, e.g., in the case of treating victims of sudden starvation events.

Role of D1-like and D2-like dopamine receptors within the ventral tegmental area in stress-induced and drug priming-induced reinstatement of morphine seeking in rats.

The ventral tegmental area (VTA) as a major source of dopamine neurons projecting to cortical and limbic regions has a crucial role in reward as well as stress processes. Dopamine is a predominant neurotransmitter in the reward system, which plays an important role in both drug priming-induced and cue-induced reinstatement of cocaine and heroin seeking. It has been shown that this neurotransmitter has a role in stress-induced relapse to drug seeking. Therefore, the present study aims to evaluate the effects of intra-VTA administration of SCH-23390, as a dopamine D1-like receptor antagonist, and sulpiride, as a dopamine D2-like receptor antagonist, on drug priming-induced and food deprivation (FD)-induced reinstatement. The rats were bilaterally implanted by two separate cannulae into the VTA. After the acquisition and extinction of morphine-conditioned place preference, the animals received different doses of SCH-23390 or sulpiride (0.15, 0.4, 1.5 and 4 mg/0.3 µl vehicle per side) into the VTA on the reinstatement day and tested for drug priming-induced reinstatement of morphine (1 mg/kg) or FD-induced reinstatement facilitated by an ineffective dose of morphine (0.5 mg/kg) in separate groups. Our findings indicated that the D1/D2-like receptor antagonists attenuated the drug priming-induced and FD-induced reinstatement. However, these decrements were more significant in groups of animals that received a 24-h FD as a stressor. The data may suggest a role for the VTA dopaminergic system in relapse to drugs of abuse, which may be induced either by re-exposure to morphine or exposure to a stressor.

Role of the orexin receptors within the nucleus accumbens in the drug priming-induced reinstatement of morphine seeking in the food deprived rats

Orexin plays a key role in mediating stress-induced drug relapse. However, the role of different types of orexinergic receptors that modulate stress-induced drug seeking remains unknown. The nucleus accumbens (NAc) has an important role in the reward system and receives orexinergic projections of the lateral hypothalamus. In addition, orexin interacts with other receptors that are involved in drug reinstatement. Therefore, in the present study, the role of orexin receptors in the NAc in morphine priming- induced reinstatement and the effect of food deprivation (FD) on drug reinstatement were examined. The extinguished morphine preference rats were tested for reinstatement following the 24-h FD condition after conditioning was induced. In the other groups, the animals were given intra-accumbal administration of SB334867 (01, 1 and 10 nM/0.5 μl DMSO) as an orexin-1 receptor antagonist and TCSOX229 (1, 5 and 25 nM/0.5 μl DMSO), as an orexin-2 receptor antagonist. The results showed that the blockade of two types of orexin receptors in the NAc remarkably attenuated the effect of FD on the drug reinstatement; however, they were more effective in FD condition. These findings indicate that the NAc is a brain area within which orexin has a fundamental role in the effect of stress on morphine-induced reinstatement and the effect of food deprivation- on the reinstatement of morphine.

First evidence of nocturnin in fish: two isoforms in goldfish differentially regulated by feeding.

Nocturnin (NOC) is a unique deadenylase with robust rhythmic expression involved in the regulation of metabolic processes in mammals. Currently, the possible presence of NOC in fish is unknown. This report aimed to identify NOC in a fish model, the goldfish ( Carassius auratus), and to study the possible regulation of its expression by feeding. Two partial-length cDNAs of 293 and 223 bp, named nocturnin-a ( noc-a) and nocturnin-b ( noc-b), were identified and found to be highly conserved among vertebrates. Both mRNAs show a similar widespread distribution in central and peripheral tissues, with higher levels detected for noc-a compared with noc-b. The periprandial expression profile revealed that noc-a mRNAs rise sharply after a meal in hypothalamus, intestinal bulb, and liver, whereas almost no changes were observed for noc-b. Food deprivation was found to exert opposite effects on the expression of both NOCs (generally inhibitory for noc-a, and stimulatory for noc-b) in the three mentioned tissues. A single meal after a 48-h food deprivation period reversed (totally or partially) the fasting-induced decreases in noc-a transcripts in all studied tissues and the increases in noc-b expression in the intestinal bulb. Together, this study offers the first report of NOC in fish and shows a high dependence of its expression on feeding and nutritional status. The differential responses to feeding of the two NOCs raise the possibility that they might be underlying different physiological mechanisms (e.g., food intake, lipid mobilization, energy homeostasis) in fish.

Reflection of the State of Hunger in Impulse Activity of Nose Wing Muscles and Upper Esophageal Sphincter during Search behavior in Rabbits.

Reflection of the state of hunger in impulse activity of nose wing muscles and upper esophageal sphincter muscles was studied in chronic experiments on rabbits subjected to 24-h food deprivation in the absence of locomotion and during search behavior. In the absence of apparent behavioral activity, including sniffing, alai nasi muscles of hungry rabbits constantly generated bursts of action potentials synchronous with breathing, while upper esophageal sphincter muscles exhibited regular aperiodic low-amplitude impulse activity of tonic type. Latent form of food motivation was reflected in the structure of temporal organization of impulse activity of alai nasi muscles in the form of bimodal distribution of interpulse intervals and in temporal structure of impulse activity of upper esophageal sphincter muscles in the form of monomodal distribution. The latent form of food motivation was manifested in the structure of temporal organization of periods of the action potentials burst-like rhythm, generated by alai nasi muscles, in the form of monomodal distribution, characterized by a high degree of dispersion of respiratory cycle periods. In the absence of physical activity hungry animals sporadically exhibited sniffing activity, manifested in the change from the burst-like impulse activity of alai nasi muscles to the single-burst activity type with bimodal distribution of interpulse intervals and monomodal distribution of the burst-like action potentials rhythm periods, the maximum of which was shifted towards lower values, which was the cause of increased respiratory rate. At the same time, the monomodal temporal structure of impulse activity of the upper esophageal sphincter muscles was not changed. With increasing food motivation in the process of search behavior temporal structure of periods of the burst-like action potentials rhythm, generated by alai nasi muscles, became similar to that observed during sniffing, not accompanied by animal's locomotion, which is typical for the increased respiratory rhythm frequency. Increased hunger motivation was reflected in the temporal structure of impulse activity of upper esophageal sphincter muscles in the form of a shift to lower values of the maximum of monomodal distribution of interpulse intervals on the histogram, resulting in higher impulse activity frequency. The simultaneous increase in the frequency of action potentials bursts generation by alai nasi muscles and regular impulse activity of upper esophageal sphincter muscles is a reliable criterion for enhanced food motivation during search behavior in rabbits.

The expression of orexigenic and anorexigenic factors in middle-aged female rats that had been subjected to prenatal undernutrition

Fetal growth retardation, which affects short- and long-term fetal brain development, is associated with metabolic, hematological, and thermal disturbances, which can increase the risk of metabolic syndrome later in life. Orexigenic and anorexigenic factors regulate food intake and energy expenditure. We studied how the expression of these factors was affected by food deprivation (FD) in middle-aged female rats that had been subjected to prenatal undernutrition. Eight pregnant rats were divided into two groups, the normal nutrition (NN) (n=4) group and the undernutrition (UN) (n=4) group, which received 50% (approximately 11g) of the daily food intake of the normal nutrition rats from day 13 of pregnancy to delivery. The pups from these dams were defined as the maternal NN (mNN) and maternal UN (mUN) groups, respectively. After weaning, all of the pups were housed and allowed ad libitum access to food and water. At the age of 6 months, both groups of pups were sub-divided into three groups. One group was allowed to consume normal amounts of food (Fed), and the other two groups were subjected to 24h or 48h FD (n=7–8 per group). The rats’ serum leptin levels and hypothalamic mRNA expression levels of various orexigenic or anorexigenic factors were measured. In both the mNN and mUN rats, the serum leptin levels of the 24h and 48h FD groups tended to be lower than those of the Fed group, and the serum leptin levels of the 24h FD mUN rats and the Fed mUN rats differed significantly. The hypothalamic neuropeptide Y (NPY) mRNA expression levels of the 24h and 48h FD groups were significantly higher in the mUN rats than in the mNN rats. In addition, among the mUN rats the hypothalamic NPY mRNA expression levels of the 48h FD group were significantly higher than those of the Fed group. In both the mNN and mUN rats, prepro-orexin mRNA expression was lower in the 48h FD group than in the corresponding Fed group. Among the mUN rats, the 48h FD group exhibited significantly lower hypothalamic proopiomelanocortin (POMC) mRNA expression than the Fed group, and a similar tendency was seen among the mNN rats. Among the mNN rats, the 24h FD group displayed significantly higher hypothalamic leptin receptor (OBRb) mRNA levels than the Fed group. However, no such differences were seen among the mUN rats. As a result, the hypothalamic OBRb mRNA expression levels of the mUN rats in the 24h and 48h FD groups were lower than those of the corresponding mNN rat groups. These findings indicate that rats that are subjected to prenatal undernutrition exhibit upregulated expression of orexigenic factors and are more sensitive to FD in middle age, which might increase their risk of developing metabolic disorders in later life.

LH and testosterone production are more sensitive to the suppressive effects of food deprivation in prenatally undernourished male rats

Although prenatal undernutrition affects the development of metabolic, physiological, and reproductive functions, it remains unclear whether it also affects physiological responses to undernutrition in adulthood. Therefore, in this study we examined whether prenatal undernutrition alters the sensitivity of the hypothalamic–pituitary–gonadal (HPG) axis to fasting in adult male rats. The offspring of ad libitum fed dams (control) and ∼50% food-restricted (during the late gestational period) dams (IUGR) were sub-divided into ad libitum fed (fed) and 48h food deprivation (FD) groups at 10 weeks of age. In each group, the serum levels of luteinizing hormone (LH), testosterone, and leptin and the hypothalamic mRNA expression levels of gonadotropin-releasing hormone (GnRH) regulatory factors were measured. The serum LH and testosterone levels of the IUGR-fed rats were significantly or tend to be higher than those of the control-fed rats, respectively. The serum LH levels of the IUGR-FD rats were lower than those of the IUGR-fed rats. Similarly, the serum testosterone levels of the IUGR-FD rats tended to be lower than those of the IUGR-fed rats. On the other hand, the serum LH and testosterone levels of the control-fed and control-FD rats did not differ. The serum leptin levels of the IUGR fed rats were higher than those of the control-fed rats. The serum leptin levels of the control-FD and IUGR-FD rats were lower than those of the control-fed and IUGR-fed rats, respectively. The hypothalamic neuropeptide Y (NPY) mRNA levels of the IUGR-FD rats were higher than those of the IUGR-fed rats. Similarly, hypothalamic NPY mRNA levels of control-FD rats were higher than those of the control-fed rats. The hypothalamic kisspeptin, kisspeptin receptor, RFamide-related peptide, GPR147, and OBRb mRNA levels of control fed rats did not differ between control-fed and IUGR-fed rats. Their mRNA levels of the fed and FD rats did not differ in the control or IUGR groups. These results suggested that prenatal undernutrition increased the basal LH and testosterone production, whereas they are easily reduced by food deprivation in male rats. Changes of serum leptin level, but not of hypothalamic reproductive related factors, might be involved in these alterations. However, the precise mechanisms responsible for these effects remain unclear.

Role of dopamine D1-like receptor within the nucleus accumbens in acute food deprivation- and drug priming-induced reinstatement of morphine seeking in rats

Dopamine is a predominant neurotransmitter in the nervous system, which plays an important role in both drug priming- and cue-induced reinstatement of cocaine and heroin seeking. Therefore, in the present study, the conditioned place preference (CPP) paradigm was used to evaluate the effects of intra-accumbal administration of SCH23390 as a dopamine D1-like receptor antagonist on food deprivation (FD) and drug priming-induced reinstatement. Sixty-eight adult male albino Wistar rats weighing 200–280g were bilaterally implanted by cannulae into the nucleus accumbens (NAc). For induction of the CPP, subcutaneous (sc) administration of morphine (5mg/kg) was used daily during a three-day conditioning phase. The conditioning score and locomotor activity were recorded by using the Ethovision software. Under extinction conditions, rats were given an ‘off’ period and were tested for FD-induced reinstatement following the 24-h or 48-h FD condition, and for drug priming-induced reinstatement under the sated condition following an injection of 0.5 and 1mg/kg (sc) morphine. In the next experiments, animals received different doses of intra-accumbal SCH23390 (0.25, 1 and 4μg/0.5μl saline) bilaterally and were subsequently tested for FD- and morphine priming-induced reinstatement. Our findings indicated that only a dose of 1mg/kg and not 0.5mg/kg of morphine induced the reinstatement of morphine. 24-h FD similar to 48-h FD induced the reinstatement of seeking behaviors facilitated by an ineffective dose of morphine (0.5mg/kg). Furthermore, the D1-like receptor antagonist attenuated FD- and drug priming-induced reinstatement dose-dependently. It is concluded that FD- and drug priming-induced reinstatement may be mediated, at least in some way, by activation of dopamine D1-like receptors in the NAc.

Enhancing hepatic mitochondrial fatty acid oxidation stimulates eating in food-deprived mice.

Hepatic fatty acid oxidation (FAO) has long been implicated in the control of eating. Nevertheless, direct evidence for a causal relationship between changes in hepatic FAO and changes in food intake is still missing. Here we tested whether increasing hepatic FAO via adenovirus-mediated expression of a mutated form of the key regulatory enzyme of mitochondrial FAO carnitine palmitoyltransferase 1A (CPT1mt), which is active but insensitive to inhibition by malonyl-CoA, affects eating and metabolism in mice. CPT1mt expression increased hepatocellular CPT1 protein levels. This resulted in an increase in circulating ketone body levels in fasted CPT1mt-expressing mice, suggesting an increase in hepatic FAO. These mice did not show any significant changes in cumulative food intake, energy expenditure, or respiratory quotient after 4-h food deprivation. After 24-h food deprivation, however, the CPT1mt-expressing mice displayed increased food intake. Thus expression of CPT1mt in the liver increases hepatic FAO capacity, but does not inhibit eating. Rather, it may even stimulate eating after prolonged food deprivation. These data do not support the hypothesis that an increase in hepatic FAO decreases food intake.

Central administration of chicken growth hormone-releasing hormone decreases food intake in chicks

Growth hormone-releasing hormone (GHRH) is well known as a stimulator of growth hormone (GH) secretion. GHRH not only stimulates GH release but also modifies feeding behavior and energy homeostasis in rodents. In chickens (Gallus gallus domesticus), on the other hand, two types of GHRH, namely, chicken GHRH (cGHRH) and cGHRH-like peptide (cGHRH-LP), have been identified. The purpose of the present study was to investigate the effect of central injection of cGHRH and cGHRH-LP on feeding behavior in chicks. Intracerebroventricular (ICV) injection of both cGHRH and cGHRH-LP (0.04 to 1nmol) significantly decreased food intake without any abnormal behavior in chicks. Furthermore, the feeding-inhibitory effect was not abolished by co-injection of the antagonist for pituitary adenylate cyclase-activating polypeptide (PACAP) or corticotropin-releasing hormone (CRH) receptors, suggesting that the anorexigenic effect of cGHRH and cGHRH-LP might not be related to the PACAP and CRH systems in the brain of chicks. Finally, 24-h food deprivation increased mRNA expression of cGHRH but not cGHRH-LP in the diencephalon. These results suggest that central cGHRH is related to inhibiting feeding behavior and energy homeostasis in chicks.

Increasing food deprivation relative to baseline influences d-amphetamine dose–response gradients

Several studies using non-pharmacological discriminative stimuli have found that stimulus control, as evident in generalization gradients, changes when motivation for (i.e., deprivation of) the relevant reinforcer is altered. Drug-discrimination studies, however, have not consistently revealed such an effect. A procedural detail that may account for the lack of a reliable effect in drug-discrimination studies is that motivation was characteristically reduced relative to the training condition in these studies. The present experiment examined how substantially increasing motivation affects d-amphetamine discrimination. Rats initially were trained to discriminate d-amphetamine (1.0mg/kg) from vehicle (0mg/kg) injections under 22-h food deprivation conditions. Dose–response gradients were then obtained under 22-h and 46-h deprivation levels. The ED50 was significantly higher with greater deprivation. This finding suggests that increasing motivation relative to the training condition may reduce stimulus control by drugs, while decreasing it may sharpen stimulus control.

Effect of food deprivation on formalin-induced nociceptive behaviors and β-endorphin and sex hormone concentration in rats.

The present study examined the possible role of endogenous opioidergic system in effect of food deprivation on formalin-induced nociceptive behaviors in male and female rats. Also, we investigated the effect of food deprivation on the plasma level of beta-endorphin and sex hormones. Food was withdrawn 48 h prior to performing the formalin test, but water continued to be available ad libitum. The formalin was injected into hind plantar paw. There is significant difference between male and female control rats during phase 2B. Following 48-h food deprivation, both male and female rats exhibited enhanced nociceptive behavior in response to formalin. Food deprivation for 12 and 24 h increased and for 48 h decreased beta-endorphin level in male and female rats. Food deprivation for 24 h decreased testosterone level in male, while it had no significant effect on female rats and food deprivation for 48 h decreased testosterone level in both sexes. Food deprivation for 24 h increased estradiol level in female and that for 48 h had no significant effect on male and female rats. The present study demonstrates the existence of food deprivation for 48 h causes enhancement of nociception in the formalin test in male and female rats that has correlation with decrease in plasma beta-endorphin and testosterone levels.