The effects of prior weight reduction on the running wheel-induced feeding suppression in rats

Adult male rats given ad lib access to food and a running wheel show an initial feeding and weight suppression. Over 6-10 days feeding recovers, but body weight remains low. It is not clear which effect is primary, the wheel-induced feeding or weight change. To test this, rats were first restricted to 15 g of food a day for 8 or 16 days to reduce their weight relative to control non-restricted rats. They were then returned to ad lib feeding and half the restricted and non-restricted control rats were introduced to the wheel either immediately (Experiment 1) or 4 days later (Experiment 2). Food intake, body weight, and wheel running were monitored throughout the experiments. At the return to ad lib feeding, prior food restriction elevated feeding. Both immediate and delayed wheel access suppressed feeding in both groups of wheel access rats compared to the appropriate control rats. Feeding history did not have a significant effect on wheel running. The wheel-induced reductions in feeding from baseline were similar in the weight reduced and normal weight animals suggesting that prior weight restriction did not prevent the onset of the wheel-induced feeding suppression. It is therefore suggested that the feeding suppression is not driven by a reduced weight set point.     

Multiple exposure to activity anorexia in rats: effects on eating,weight loss,and wheel running

Animals were given five cycles of an activity anorexia (AA) procedure in order to determine the effect of additional experience on eating, running, and weight loss. Female Sprague-Dawley rats were given a 1h meal and allowed access to a running wheel for the remainder of each day. Upon reaching 75% of free-feeding body weight, each animal was denied wheel access and given ad libitum food until it regained the lost weight. Then, food was again restricted and wheel access provided. Sedentary control animals were placed on the restricted feeding schedule for the median number of days experimental animals required to reach weight loss criterion. Experimental animals showed adaptation by increasing food consumption and decreasing the rate of weight loss despite an increase in running across cycles. Additionally, the distribution of running shifted gradually so that during the later cycles, much of the running occurred in the hours just before feeding. The results support the hypothesis that running interferes with adaptation to the restricted feeding schedule and also that the marked increase in anticipatory behavior during the later cycles is primarily responsible for the maintenance of AA.     

剥夺食物对雄性长爪沙鼠贮食行为的影响

禁食导致一些啮齿动物的贮食量增加,但禁食处理后雄性长爪沙鼠贮食行为的变化则不一致。每天禁食22 h,长爪沙鼠的一些个体表现出高水平的贮食行为(禁食贮食组),而另一些个体则没有表现出贮食行为(禁食无贮食组)。延长禁食(22 h)持续的时间(连续重复3 d 和20 d)和增加禁食时间(禁食48 h),都没有使禁食无贮食组的动物表现出贮食行为。同样在自由取食条件下,长爪沙鼠的贮食行为也表现为二型性。在自由取食和禁食条件下,贮食量与体重、体脂含量和瘦素的浓度之间无明显相关关系。研究结果表明,禁食是诱导雄性长爪沙鼠贮食行为发生的一个重要条件,但增加禁食的程度并不改变其贮食行为的表现。     

A comparative analysis of feeding and hoarding in hamsters and gerbils

Male and female hamsters and gerbils were randomly assigned to one of three groups. The animals were tested under ad lib feeding conditions or food deprived until they had lost either 10% or 20% of their predeprivation body weight. They were given a 30-min. hoarding test for three consecutive days. The results indicated that although food-deprived gerbils ate more than control gerbils, deprivation had no significant effect on the food intake of hamsters. A sex difference was also evident in the food intake of gerbils; males ate more than did females. Although there was a sex and species difference in the amount of hoarding, deprivation had no significant effect on the amount of hoarding. The implications of these results for of different models of hoarding are discussed. These models contrast hoarding as a defensive response in the regulation of body weight or as an anticipatory activity that is influenced by other selection pressures.     

Hoarding versus the immediate consumption of food among hamsters and gerbils

This project dealt with a comparative analysis of the effects of food deprivation on feeding and hoarding in hamsters and gerbils. The animals were given food in their home cage and their food intake was measured during a 30-min period after which they were transferred to an apparatus in which hoarding behaviour was assessed. The results indicated interesting species differences in the animals' reactions in the test situations. Whereas food-deprived gerbils ate more food than nondeprived gerbils, the food intake of hamsters was not significantly enhanced by deprivation. In the hoarding test, although significant differences were observed between deprived and nondeprived gerbils, the absolute level of hoarding in gerbils was very low in comparison to that of hamsters tested under the same conditions. These results suggest that hamsters and gerbils respond to challenges to their food reserves with different strategies.     

Enhanced Food Anticipatory Activity Associated with Enhanced Activation of Extrahypothalamic Neural Pathways in Serotonin2C Receptor Null Mutant Mice

The ability to entrain circadian rhythms to food availability is important for survival. Food-entrained circadian rhythms are characterized by increased locomotor activity in anticipation of food availability (food anticipatory activity). However, the molecular components and neural circuitry underlying the regulation of food anticipatory activity remain unclear. Here we show that serotonin_2C receptor (5-HT2CR) null mutant mice subjected to a daytime restricted feeding schedule exhibit enhanced food anticipatory activity compared to wild-type littermates, without phenotypic differences in the impact of restricted feeding on food consumption, body weight loss, or blood glucose levels. Moreover, we show that the enhanced food anticipatory activity in 5-HT2CR null mutant mice develops independent of external light cues and persists during two days of total food deprivation, indicating that food anticipatory activity in 5-HT2CR null mutant mice reflects the locomotor output of a food-entrainable oscillator. Whereas restricted feeding induces c-fos expression to a similar extent in hypothalamic nuclei of wild-type and null mutant animals, it produces enhanced expression in the nucleus accumbens and other extrahypothalamic regions of null mutant mice relative to wild-type subjects. These data suggest that 5-HT2CRs gate food anticipatory activity through mechanisms involving extrahypothalamic neural pathways.     

The effect of feeding strategies and body weight on growth performance and hematological parameters of Siberian sturgeon (Acipenser baerii,Brandt 1869): Preliminary results

The purpose of present study was to investigate the growth performance and hematological parameters of Siberian sturgeon Acipenser baerii in three feeding strategies (satiation feeding, restricted feeding and starvation). We considered two body weights 465.75 ± 11.18 g and 250.40 ± 12 g for large fish and small fish, respectively. In a 45‐day experiment, eighteen fiberglass tanks were used for six triplicate treatments. In restricted feeding strategy, the fish were fed to 50% of satiation and starved treatments were an absolute feed deprivation throughout the experiment. At the end of 45‐day period, the hematological parameters were measured. The reduction of weight, condition factor and daily growth rate in the smaller fish was dramatically higher than the larger fish. Feed deprivation increased the rate of weight loss. Specific growth rate were negative in the large and small fish of starved treatments. The hematological results revealed no significant differences in except for the number of monocytes in larger fish. Large satiated fish showed the highest number of monocytes. In general, these strategies (restriction and deprivation) did not have any negative impacts on the hematological parameter in both sizes but respect to fish body weight, difference in total feed input between satiated and restricted treatments changed growth performance. It seems that restricted feeding (50% of satiation) in large fish was enough to achieve optimal growth while the amount of feed provided for small fish was not enough. Therefore; we can conclude that the restricted feeding is an effective strategy in rearing sturgeon at higher weight when the rearing condition is unsuitable.     

完全或部分的食物剥夺对中华鳖(Pelodiscus sinensis)幼体补偿生长反应的影响:生长率的时间变化模式与体组成的变化

为了探究中华鳖（Pelodiscus sinensis）幼体的补偿生长能力,我们对中华鳖幼鳖（平均湿重9．56g）进行如下6种处理：饥饿0（对照）、1、2、3、4周,或者食物限制4周,即只投喂体湿重百分之一的食物;然后对各组进行饱食处理直到10周的实验结束为止。结果发现在饱食期的第一周各饥饿处理组的特殊生长率均显著高于对照组（P〈0．05）,但是终体重均没有赶上对照组。当饥饿或食物限制结束时,脂肪含量随着饥饿期的延长而降低,灰分和水分则表现出相反的变化趋势：脂肪含量显著低于对照（P〈0．05）,而灰分和水分则显著高于对照（P〈0．05）。蛋白含量则没有显著变化（P〉0．05）。实验结束时,除了灰分外（P〈0．05）,其他个体组成指标均恢复到对照组的水平。以上结果表明中华鳖幼体在饥饿胁迫下首先利用脂肪作为主要能源以维持生存,以及在该研究条件下完全的食物剥夺可以诱发其部分补偿生长反应．而部分食物剥夺则不能诱发此反应。     

Compensatory Growth in Juveniles of Freshwater Redclaw Crayfish Cherax quadricarinatus Reared at Three Different Temperatures: Hyperphagia and Food Efficiency as Primary Mechanisms

Feeding restriction, as a trigger for compensatory growth, might be considered an alternative viable strategy for minimizing waste as well as production costs. The study assessed whether juvenile redclaw crayfish Cherax quadricarinatus (initial weight 0.99 ±0.03 g) was able to compensate for feeding restriction at different temperatures (23±1, 27±1 and 31±1°C). Hyperphagia, food utilization efficiency, energetic reserves, and hepatopancreas structure were analyzed. Three temperatures and two feeding regimes (DF-daily fed throughout the experiment and CF- 4 days food deprivation followed by 4 days of feeding, intermittently) were tested. The restriction period was from day 1 to 45, and the recovery period was from day 45 to 90. The previously restricted crayfish held at 23, 27, and 31 ± 1°C displayed complete body weight catch-up through compensatory growth following the restriction period with depressed growth. The mechanisms that might explain this response were higher feed intake (hyperphagia), and increased food utilization efficiency. Hepatopancreatic lipids were used as a metabolic fuel and hepatosomatic index was reduced in the previously restricted crayfish, but recovery at the same level of unrestricted crayfish occurred after the shift to daily feeding. The highest temperature affected adversely growth, feed intake, food efficiency, and metabolism of crayfish, whereas the lowest temperature and feeding restriction induced a more efficient growth of the crayfish.     

Energy and water balance during torpor and hydropenia in the pigmy gerbil,Gerbillus pusillus

Summary Under ad lib. food conditions,G. pusillus used 107% of the predicted daily energy expenditure. This increased significantly with water deprivation to 116% of the allometric expected value, thereby reflecting an increase in activity in search of food with high moisture content, a shift to metabolic water for meeting the animal's water requirements and a change in the state of hydration of the animal. Economic water expenditure through efficient kidney concentrating ability, reduced pulmocutaneous evaporation, reduced faecal water loss, and tolerance to haemoconcentration, was sufficient to impart virtual independence of exogenous water. Gerbillus pusillus responded to food shortage by abandoning homeothermy. In doing so, it was able to maintain a fairly stable body mass by monitoring energy intake and ensuring that energy expenditure did not exceed intake. There was no significant difference in energy expenditure between gerbils on a restricted energy intake and ad lib. water and those gerbils on a restricted energy intake and no water. Both these experimental groups were able to maintain a positive water balance, for whilst less metabolic water was available, water loss primarily through evaporation decreased concomittantly with reduced body temperature. In addition, the volume of urine excreted when torpid accounted for approximately 5% of the volume excreted by coenothermic rodents deprived of free water. Urine, although less concentrated than that of non-torpid gerbils deprived of water, was ten times more concentrated than the plasma. Daily torpor, although uniquely suited to energy conservation, is not without cost. A reduced body temperature resulted in a decline in ‘apparent assimilation efficiency’ (AE). It seems therefore that the cost of maintaining an elevated body temperature for the full duration of digestion is impractical. The cost of employing torpor as calculated from the reduced AE of food (0.5 kJ·day⁻¹), was however insignificant in comparison to the savings accured (32.25 kJ·day⁻¹) by the use of torpor.     

The effects of feeding regime on proximate body composition and patterns of energy deposition in juvenile Arctic charr, Salvelinus alpinus

Juvenile Arctic charr, Salvelinus alpinus , subjected to either food deprivation or restricted feeding showed reductions in relative sizes of both liver and viscera. With food deprivation, percentage lipid decreased and percentage water increased in the eviscerated carcass, which is in agreement with findings for several other fish species. Following transfer from a restricted to a satiation feeding regime, the relative sizes of both liver and viscera increased to levels exceeding those of fish fed continuously to satiation. At the end of the experiment the percentage liver lipid content of restricted-satiation fed fish was higher than in fish fed to satiation. These differences in energy deposition patterns were, however, not sufficiently large to produce marked differences at the whole animal level, since whole body lipid energy: protein energy ratios and energy utilization efficiencies were similar for restricted-satiation and satiation fed fish.     

Anticipatory activity rhythms under daily schedules of water access in the rat.

Rats anticipate a fixed daily feeding time by entrainment of a component of their multioscillatory circadian system. The range of stimuli capable of entraining this component is little studied. Previous studies suggest that restricted water access is not an effective entrainment stimulus, as measured by general locomotion. The present study re-examined the issue, using two other measures of activity: wheel running and activity at a food-water delivery bin. Rats restricted to 1 hr of water each day in the middle of the light and to food in the 12-hr dark period showed no anticipation of this event in the wheel-running measure, but some rats did show anticipation in the delivery bin activity measure. Rats (bin activity measure only) restricted to 1 hr of water and 1 hr of food separated by intervals of 7, 10, or 12 hr, in either the light or the dark, showed consistent anticipation of food access time but little or no anticipation of water access time. Water access time also did not sustain food anticipatory rhythms in animals whose food-water schedules were reversed. However, deprivation of water or of both food and water for 72 or 90 hr was usually associated with specific increases in bin activity at both the usual feeding and drinking times. Water access, like food, appears to provide cues capable of entraining an anticipatory circadian mechanism. Differences in the type and amount of anticipatory activity preceding these events may reflect differences in the strengths of the two entrainment cues and/or in the activity levels or specific behavioral strategies promoted by hunger and thirst.     

The distribution of water in the intracellular and extracellular compartments and the lipid and protein composition of the Mongolian gerbil (Meriones unguiculatus) during water deprivation.

1. The plasma, interstitial, extracellular and intracellular volumes fell to similar extents after 5 days of water deprivation in male and female gerbils. There was no selective plasma volume conservation. 2. The female gerbils lost more weight on water deprivation yet the total body water loss was very similar to that in the male animals. While there was a small fall in the protein content of the male animals the extra loss of weight in the females appeared to be due to the considerable catabolism of lipid stores.     

Effects of prior or concurrent food restriction on amylin-induced changes in body weight and body composition in high-fat-fed female rats

Amylin infusion reduces food intake and slows body weight gain in rodents. In obese male rats, amylin (but not pair feeding) caused a preferential reduction of fat mass with protein preservation despite equal body weight loss in amylin-treated (fed ad libitum) and pair-fed rats. In the present study, the effect of prior or concurrent food restriction on the ability of amylin to cause weight loss was evaluated. Retired female breeder rats were maintained on a high-fat diet (40% fat) for 9 wk. Prior to drug treatment, rats were either fed ad libitum or food restricted for 10 days to lose 5% of their starting body weight. They were then subdivided into treatment groups that received either vehicle or amylin (100 microgxkg(-1)xday(-1) via subcutaneous minipump) and placed under either a restricted or ad libitum feeding schedule (for a total of 8 treatment arms). Amylin 1) significantly reduced body weight compared with vehicle under all treatment conditions, except in always restricted animals, 2) significantly decreased percent body fat in all groups, and 3) preserved lean mass in all groups. These results indicate that amylin's anorexigenic and fat-specific weight loss properties can be extended to a variety of nutritive states in female rats.     

Insights into How Longicorn Beetle Larvae Determine the Timing of Metamorphosis: Starvation-Induced Mechanism Revisited

Larvae of holometabolous insects must determine the timing of their metamorphosis. How they determine this timing has only been studied in detail for a few insect species. In a few species of Coleoptera, starvation is known to be a cue for metamorphosis, leading to the formation of smaller adults (starvation-induced pupation, SiP). We investigated the occurrence of SiP in the beetle Psacothea hilaris. When P. hilaris larvae were starved late in the feeding phase of the last (5th) instar, they exhibited typical SiP characterized by constancy of the time from food deprivation to pupation (TTP) irrespective of the body weight upon food deprivation or the length of prior feeding. In contrast, when larvae were starved early in the feeding phase, TTP decreased by roughly 1 day as the feeding became 1 day longer. The change in the response to starvation was estimated to occur on day 5.9 in the last instar. A series of refeeding experiments suggested that whereas SiP occurred readily in the larvae starved in the late feeding phase, activation of SiP was suspended until day 5.9 in the larvae starved early in the feeding phase. When P. hilaris larvae were fed continuously, they eventually ceased feeding spontaneously and pupated. The time length between spontaneous cessation of feeding and pupation was approximately equal to the TTP in SiP. This suggests that the same mechanism was activated by food deprivation in the late feeding phase and by spontaneous cessation of ad libitum feeding.     

The influence of previous feeding regime on the compensatory growth response of maturing and immature Arctic charr, Salvelinus alpinus

Alternating periods of food deprivation with those of unlimited provision of food depressed the growth of Arctic charr, Salvelinus alpinus , below that of controls. Fish that were deprived of food and then fed on alternate weeks (1:1) were larger than those that were exposed to periods of 1 5- or 3-week deprivation and feeding (1·5:1·5 or 3:3). On receiving excess food supplies following 24 weeks on the restricted feeding regimes the previously-restricted fish grew more rapidly than the controls. The greatest compensatory growth was displayed after the 3:3 regime, followed by the 1·5: 1·5 and then the 1:1 feeding regime. At the termination of the experiment there were no significant differences in body weight between fish fed according to the different regimes during the period that food restriction was imposed. Growth patterns of the immature males and females were similar, but mature males were significantly lighter than the immature fish by the end of the experiment. Both immature and maturing fish displayed a compensatory growth response on return to adequate feeding. Beginning food restriction in May did not influence the proportions of male fish ( c . 60%) which were mature in the autumn.     

Recovery growth following periods of restricted rations and starvation in rainbow trout Salmo gairdneri Richardson

Fingerling rainbow trout (6.9 to 11.6 cm fork length) maintained at 12° C were either: fed restricted rations (3% of dry body weight/day) for 16 weeks, or starved for 3 weeks (14.5% weight loss), or for 13 weeks (32.5% weight loss). Whole body wet weights and dry weights (as % of wet weight), and wet and dry weights of tissues (heart, spleen, liver, skin, gonad, gut, visceral fat, and 'carcase') resulting from these treatments were compared to corresponding weights of an 'initial sample'. Visceral fat was completely utilized during both short and long-term starvation and gut was significantly reduced in the extended starvation group.
During subsequent recovery growth on full rations, following food deprivation, fish grew at approximately the same rate as fully-fed controls, which had not suffered food deprivation, as regards body wet weight and condition ( K ), but tended to surpass controls in % dry weight.
Heart, liver, gonad, gut and visceral fat also increased during recovery growth in a manner suggestive of overcompensation in response to former food deprivation. Gut, skin and carcase dry weights were less in the control, and in the 14.5% weight loss groups following recovery growth than in those in 3% rations and in the severely starved group, indicating that the effects of slow growth resulting from limited rations resemble those of severe starvation more than those of limited starvation.     

Hamsters' demand for food to eat and hoard as a function of deprivation and cost

Unlike many other species, golden hamsters (Mesocricetus auratus) do not compensate for a loss in weight following a brief period of food deprivation: this may be due to their adaptation for a hoarding mode of life. We studied the interaction of hoarding with deprivation and a second challenge to body weight, increasing food costs. Hamsters earned all their food in operant chambers, in which they lived. The cost of food was varied by making it available on several different fixed ratio schedules. Regardless of whether the hoard was taken away each day (experiments 1 and 3) or left intact (experiments 2 and 4), food consumption was virtually constant as cost increased, but hoarding declined sharply. Hoarding was enhanced by a short deprivation period (experiment 3) especially when the subsequent cost of food was low (experiment 4). The results suggest that hamsters do indeed show compensatory behaviour following deprivation, or when the cost of foraging is high, but its form is different from that seen in non-hoarding species.     

Estrogenic regulation of body weight in the female rat.

For a period of weeks subsequent to bilateral ovariectomy, female rats given unlimited access to food increased their food intakes and the rates at which they gained body weight; this resulted in elevated levels of body weight. Restricting ovariectomized (ovx) rats to their preoperative level of food intake (restricted diet), prevented this excessive gain in body weight. Estradiol benzoate (EB) treatments of 0.5 μg per day for 15 consecutive days partially reversed pre-occurring weight gain in obese ovx rats; this was accompanied by a reduction in food intake. In contrast, identical EB treatment for nonobese ovx rats (restricted diet) did not result in any loss of body weight or change in food intake. Oil-treated nonobese ovx rats gained a small amount of weight relative to their EB-treated counterparts, despite the similarity in their food intakes. Thus, part of the increased weight gain observed after ovariectomy may be independent of changes in food consumption, and related to removal of estrogenic influences from metabolic and behavioral processes involved in energy balance. The weight limiting actions of estradiol were far more pronounced in animals already obese or facing impending obesity than in animals in which excessive weight gain was prevented. The data also suggest that estradiol is more effective in preventing than in reversing the weight gain associated with ovariectomy, and that estrogenic influences on the body weight set point are manifested with very short latencies. These findings support earlier conclusions that estradiol does not regulate food intake directly, but secondarily controls consumption as a means of weight regulation.     

Effects of androgens on body weight, feeding, and courtship behavior in the pigeon

Adult male pigeons, some intact and some castrated in adulthood, were housed in individual cages kept in an isolated room with temperature and lighting controlled. Weekly measurements were made of ad lib. food intake and body weight for 4 mo after surgery. Castration was followed by a significant depression in body weight and by initially depressed but then progressively enhanced feeding. Food deprivation elicited an increase in food intake proportional to body weight loss, but castrates consumed less food at 100%, 90%, and 80% of ad lib. feeding weight than either intact birds or castrates treated daily with testosterone propionate (TP). Castrates gained weight and ate more than controls in response to daily treatments (im) with TP (6 mg/400 g) or 5a-dihydrotestosterone (DHT, 6 mg/400 g), while androstenedione (15 mg/400 g) and androsterone (15 mg/400 g) were ineffective. Administration of 100 mg DHT (sc) to castrates produced a significant enhancement of body weight without elevating the level of food intake. The biological potency of these diverse androgens on male courtship behavior was reciprocal to that for weight-promoting potency. The results suggest that the structural requirements of the androgen molecule for promoting body weight differ from those for stimulating sexual behavior.