Subdiaphragmatic vagal deafferentation fails to block the anorectic effect of hydroxycitrate

We investigated the neural mediation of the feeding suppression through orally administered hydroxycitrate (HCA) in male rats that were fed a high-glucose diet (about 48% glucose). Ten-day ad libitum food intake and body weight regain after previous body weight loss (13% of initial body weight) due to restrictive feeding were measured in rats with sham deafferentation (SHAM; n = 6), subdiaphragmatic vagal deafferentation (SDA; n = 7), and SDA plus celiac-superior mesenteric ganglionectomy (SDA/CGX; n = 9). HCA suppressed the 10-day cumulative food intake in all surgical groups and body weight regain in SDA and SDA/CGX groups. Independent of HCA, SDA and SDA/CGX rats consumed less food and gained less weight compared to SHAM rats. These results demonstrate that all vagal afferents from below the diaphragm and vagal efferents of the dorsal trunk as well as splanchnic nerves (afferents and efferents) are not necessary for the feeding-suppressive effect of HCA in this animal model. Vagal afferents, however, appear to play a role in the control of intake when a high-glucose diet is consumed after a period of restrictive feeding.     

Chronic food restriction and reduced dietary fat: risk factors for bouts of overeating

The purpose of this study was to determine the effect of chronic food restriction and reduced dietary fat on feeding behavior and body weight. Young female rats were fed ad lib or food restricted on a low-fat (LF) or a fat-free (FF) diet for 4 weeks. Rats then received 24-h free access to 2 diets, the maintenance diet (LF or FF) plus a novel high-fat (HF) diet (24-h intake test). After the test, all the rats were allowed chronic free access to the HF diet until body weight was stable. During the 24-h test, the restricted groups ate significantly more calories than the ad lib groups, and the FF-restricted rats ate significantly more total food, carbohydrate and protein than the LF-restricted rats; there were no differences between the two ad lib groups. During chronic free access to the HF diet, the formerly restricted rats achieved and defended lower body weights than the formerly non-restricted rats. Throughout the experiment, the ad lib groups had more body fat than the restricted groups independent of the dietary subgroup. Hence, a history of chronic food restriction predisposes to consuming more food in acute feeding situations, particularly when dietary fat is reduced, and lowers the level of body weight maintained and defended. Chronic food restriction accompanied by reduced dietary fat may increase risk for bouts of overeating.     

Absence of post-fast food compensation in the golden hamster (Mesocricetus auratus).

Ad lib food intakes and body weights were measured for hamsters fed one of 4 different diets. Animals were then placed on an intermittent starvation (IS) schedule in which food was available ad lib on alternate days only. Hamsters of both sexes showed little or no post-fast food compensation, i.e., after 24 hr of food deprivation their daily food intake was no greater than their daily intake during baseline testing. These animals lost a large percentage of their initial body weight and many of them died. Other hamsters restricted daily to half-day feeding periods that nearly coincided with the light (L) or dark (D) phases of the illumination cycle also failed to show food compensation; they generally ate no more during D- or L-periods that followed a half day of food deprivation than during D- or L-periods that succeeded a half day of ad lib feeding. These animals lost substantial portions of their initial body weight and many died. Hamsters refed after a 96-hr fast and an 18% loss in body weight also did not increase their food intake substantially above baseline values. In each of these experiments substantial portions of the body weight lost during starvation were not regained during extended ad lib refeeding regimens. These findings contrast strikingly with the behavior of rats tested concurrently; rats showed a dramatic post-fast hyperphagia, rapid recovery of body weight lost during starvation, and a reversal of the normal nocturnal feeding pattern when refeeding began during L-periods. Hamsters' nocturnal rhythms of eating and drinking were remarkably stable in the face of all the experimental manipulations. However, hamsters, as well as rats, were quite effective in compensating for changes in diet density; a 1:1 dilution of a liquid diet produced a prompt doubling in the volume of diet ingested. Impressive but less complete compensation was recorded when solid diets were diluted with inert substances (kaolin, cellulose). Hoarding and perhaps hibernation rather than compensation may have evolved as adaptations to periods of food scarcity. Noncompensation may be related to hamsters' nonresponsiveness to some signal of energy depletion. The possibility of lipogenesis being a rate-limiting step is considered. The desirability of adequate field data as a prerequisite to laboratory analysis of feeding behavior is emphasized.     

Maternal malnutrition in the rat: Effects on food intake and body weight

The effects of dietary protein level on food intake and body weight were examined in adult female rats during a 35-day pre-mating period and during gestation and lactation. During the pre-mating period, no differences in daily food intake were observed among rats fed a 6% casein, 8% casein or 25% casein diet. However, during this period, rats fed the 6% casein diet gained significantly less weight than those with ad lib access to the 8% or 25% casein diets or than rats pair-fed the 25% casein diet in amounts equivalent to that consumed by rats in the 6% or 8% casein groups. Additionally, rats fed the 6% casein diet displayed decreased efficiency of energy utilization, calculated as weight gain per 100 kilocalories consumed, relative to rats fed the 8% or 25% casein diets. No differences in food intake were observed among the groups during gestation. However, rats fed the 6% casein diet gained less weight than rats fed the 8% or 25% casein diets. During lactation rats fed either the 6% or 8% casein diet consumed significantly less food than animals given the 25% casein diet ad lib. During the second week of lactation, rats receiving ad lib access to the 25% casein diet gained weight while those receiving the 6% or 8% casein diets continued to lose weight. At parturition, body weights of pups did not differ as a function of dietary condition. However, by day 12 of life, pups whose dams had ad lib access to the 25% casein diet weighed significantly more than pups whose dams consumed the 6% or 8% casein diet or whose dams were pair-fed the 25% casein diet in amounts equivalent to those consumed by rats fed the 6% or 8% casein diet.     

Taste or diet balancing?

Two groups of adult male rats were given ad lib access to a nutritionally complete diet (Purina Chow) and either a 32%-sucrose solution (w/v) or a separate container of dextrinized starch. A control group was allowed access only to Purina Chow. All groups consumed the same total caloric intake. Further, the composition of the diets selected by the two carbohydrate groups did not differ, although rats with access to sucrose gained weight at a signficantly greater rate than the starch group or the control group. These results suggest that the balance between dietary items plays an important role in the selection of food items and that the mechanism used in determining balance is not based on factors such as taste or feedback from body weight.     

Differential effects of chow and purified diet on the consumption of sucrose solution and lard and the development of obesity

Obesity has been associated with increased consumption of sweetened beverages and a high-fat diet. We determined whether the composition of the dry pellet offered with liquid sucrose (LS) and lard influenced the development of obesity. We hypothesized that animals offered LS or LS and lard (choice), in addition to chow or purified low fat diet pellet (LFD; 10% fat), would gain more body fat than controls. We compared the effects of LFD vs. chow on voluntary consumption of LS and lard, serum triglyceride (TG), glucose, and body fat over 21 days. Male Sprague Dawley rats (n=10/group) were offered chow, chow+LS, chow choice, LFD, LFD+LS, LFD choice or solid high-sucrose diet (70% sucrose). Energy intakes of rats fed chow, LFD, and high-sucrose diets were similar. Energy intake was increased by 16% in chow+LS, 15% in LFD+LS, 11% in LFD choice, and 23% in chow choice rats. Chow choice rats consumed 142% more lard than LFD choice rats. Fasting glucose increased in all choice rats compared with the chow and high-sucrose diet rats. Fasting TG increased in LFD choice rats and were ~75% higher than those of chow, LFD, or high-sucrose rats. Chow choice had higher carcass fat than chow, chow+LS, and LFD groups however LFD choice was not different from their controls. Another experiment confirmed rats consumed 158% more lard when given chow choice compared to LFD choice. The diet offered to rats with free access to LS and lard influenced the development of obesity, sucrose and lard selection, and TG.     

Effect of dietary macronutrients on food intake, body weight, and tail width in the marsupial S. crassicaudata

The role of dietary fat, as opposed to total energy intake, in the etiology of obesity is controversial. The aim of this study was to determine the effect of macronutrient content, specifically changes in dietary fat on body weight, fat stores, and food intake in S. crassicaudata, a marsupial that stores about 25% of total body fat in its tail. Female animals were divided into three groups (n = 7-9) matched for food intake per gram of body weight. Each group of animals was fed, ad lib an isocaloric diet (1.01 kcal/g), which contained either 10, 20, or 40% of calories from fat. Body weight, food intake, and tail width (an index of body fat stores) were measured daily. Over 21 days, cumulative energy intake was less (p = 0.026) in the 40% fat group compared to the 10% fat group. Despite the differences in food intake, body weight in each group remained stable throughout the study, so that at day 21 there were no differences in the body weights between the three groups. In contrast, tail width increased in the animals who received the 40% fat diet compared to either the 10% (p = 0.016) or 20% (p = 0.001) fat intake groups, whereas there was no significant change in tail width in either of these two groups. These observations indicate that macronutrient composition has a role, independent of total calories in the regulation of food intake and body fat stores, specifically that dietary fat promotes adiposity, independent of total caloric intake.     

The effects of intermittent dietary restriction on weight gain and body fat in white-footed mice, Peromyscus leucopus

The effects of repeated food restriction-refeeding cycles were investigated in second generation captive Peromyscus leucopus. Mice were maintained on 50% of their individual predetermined ad lib diet for 5 days followed by 10 days of refeeding ad lib. Cycles were repeated 3 times. When compared with controls maintained ad lib for the same time period, no significant differences in final weight or fat content were observed. Restricted-refed mice were, however, observed to both lose and regain weight at increasing rates with each subsequent cycle.     

Dietary self-selection vs. complete diet: body weight gain and meal pattern in rats.

Food intake and body weight gain of male adult Wistar rats were examined in two groups of animals. One group (n = 14) was allowed to select its diet from separate sources of protein (casein, 3.1 kcal/g), fat (lard and sunflower oil, 7.9 kcal/g) and carbohydrate (CHO, starch and sucrose, 3.3 kcal/g). Another group (n = 10) received a nutritionally complete diet (3.3 kcal/g). After 2 weeks of adaptation to the diets, body weights and meal patterns were recorded for at least 4 days. The total caloric intake was nearly identical for the two groups of rats. Rats given dietary choice gained less weight over 4 days than rats fed chow and showed reduced feed efficiency. During the 24-h period, self-selecting rats consumed 20.8% of calories as proteins, 21% as fats and 58.2% as CHO. Self-selecting rats ate significantly less calories during the day than did rats given chow. The chow diet consisting of 17.3% calories as protein, 7.6% as fat and 75.1% as CHO. When comparing the self-selecting group nutrient intakes to those of chow-fed group it was observed that 24-h protein calorie intakes were identical in both groups. Fat intake was significantly higher and CHO reduced as compared to chow-fed rats. During the day, CHO intake was higher in self-selecting rats, and fat intake was not significantly reduced. During the night, protein and fat intakes were significantly higher in self-selecting rats, while CHO intake was significantly decreased, particularly in the last periods of the night.(ABSTRACT TRUNCATED AT 250 WORDS)     

Long-term effects of exogenous leptin on body weight and fat in post-obese female rats.

This study was designed to test the hypothesis that short-term leptin infusion during the post-obese refeeding phase of weight-reduced rats would reduce the rate of weight regain and, as a result, reduce the final body weight and fat content in weight-reduced rats. Ninety-six female Wistar rats were divided into four groups: (1) LFCON (low-fat control) group: Rats in this group were fed the control low-fat (LF) diet ad lib for the entire study period. (2) HFCON (high-fat control) group: Rats in this group were fed the high-fat (HF, 40% fat) diet ad lib for the study period. (3) HFRLP (high-fat fed, weight-reduced, leptin treatment) group: Obese rats in this group were weight-reduced and received leptin infusion for 2 weeks (miniosmotic pumps, 0.5 microg/kg/day) during the post-obese refeeding period. (4) HFRSM (high-fat fed, weight-reduced, sham control) group: Rats in this sham-control group were treated the same as the rats in the HFRLP group with the exception that no leptin was actually infused during the first 2 weeks of refeeding period. The results demonstrated that 2 weeks of leptin treatment during the early refeeding phase did not prevent weight regain in weight-reduced rats, but it significantly reduced body fat content in these rats as compared to ad lib fed obese control rats. One cycle of weight reduction and regain did not alter the body weight and body fat content in HFRSM rats when compared to obese control rats. Therefore, leptin treatment was effective in reducing body fat content in post-obese rats for up to 7 weeks, but the long-term effect of short-term leptin treatment needs to be further examined.     

The effects of a high-energy diet on hippocampal-dependent discrimination performance and blood-brain barrier integrity differ for diet-induced obese and diet-resistant rats

Rats that consume high-energy (HE) diets (i.e., diets high in saturated fats and sugar) show impaired hippocampal-dependent learning and memory (e.g., Kanoski and Davidson (2011) [1]). To further investigate this effect, we trained rats given restricted access to low-fat lab chow on hippocampal-dependent serial feature-negative (FN) and hippocampal-independent simple discrimination problems. When training was completed, Group Chow received ad libitum lab chow. The remaining rats received ad libitum HE diet. Performance on both discrimination problems was tested following 7, 14, 21 and 28 days of HE diet exposure. FN, but not simple discrimination, was abolished initially for all rats, and then re-emerged for Group Chow. For rats fed HE diet, those that weighed the least and had the lowest amount of body fat (HE-diet resistant (HE-DR) rats), performed like Group Chow on both discrimination problems. However, HE diet-induced obese (HE-DIO) rats (i.e., rats that weighed the most weight and had the most body fat) performed like Group Chow on the simple discrimination problem, but were impaired throughout testing on the FN problem. Subsequent assessment of blood-brain barrier (BBB) permeability revealed that concentrations of an exogenously administered dye were elevated in the hippocampus, but not in the striatum or prefrontal cortex for HE-DIO rats relative to the HE-DR and Chow groups. The results indicate that the adverse consequences of HE diet on hippocampal-dependent cognitive functioning are associated with detrimental effects on the BBB and that both of these outcomes vary with sensitivity to HE diet-induced increases in weight and adiposity.     

Physiological effects of dieting and bingeing in rats.

Female rats were assigned to dietary conditions as follows for 3.5 months: 1) Low-fat control (LFC); 2) Moderately high-fat control (HFC); 3) Alternation between restricted access to a low-fat diet and ad lib access to a very high fat diet (RA); 4) Unrestricted access to the same diets as RA (URA). Results indicate that: 1) HFC consumed the same energy as LFC, but showed a tendency to become heavier and fatter through greater food efficiency. 2) URA and LFC did not differ in body weight, food intake, body composition or energy efficiency. 3) Intake of the very high fat diet declined over time in the RA. 4) RA ate less total calories, weighed less than all other groups, and showed a tendency for decreased percentage body fat and increased percentage of weight gained due to FFM gained. Results provide no evidence that dieting and bingeing promote obesity or increased preference for dietary fat, and suggest that dietary restriction has greater impact on energy balance and body composition than does alternation of diet composition.     

Short-term taste behavior and copper/vitamin B-6 nutriture in Long-Evans rats

The taste behavior of rats subjected to dietary depletions of copper and/or vitamin B-6 was tested. Weanling rats were fed casein-based methionine supplemented diets according to a 2 X 2 factorial design: -Cu/-vitamin B-6; -Cu/+vitamin B-6; +Cu/-vitamin B-6; +Cu/+vitamin B-6. Short-term (18 min) taste tests were conducted daily to assess the effects of the dietary treatment on taste stimuli intake behavior; body weight and ad lib food and water consumption were monitored during the study. These measures showed that dietary copper deficits had no apparent effect on growth, ingestive behavior or short-term intake of preferred taste stimuli but did cause a marginal depression in the short-term intake of quinine solution. In contrast, vitamin B-6 depleted rats reduced their ad lib consumption of food and water, failed to grow and exhibited elevated taste stimuli intake during short-term tests.     

Effects of abuse pattern of gestational toluene exposure on metabolism, feeding and body composition

AIMS: Inhalant abuse during pregnancy lowers birth weight and impedes early development. These studies explored the effects of brief, repeated, prenatal toluene exposures in pregnant female rats on body weight, metabolic rate, body composition, and food intake in their offspring. METHOD: Rats were exposed to 0, 8000, 12,000, or 16,000 ppm of toluene twice daily for 15 min from gestational days 8 to 20. The effects of such exposures on post-weaning litter weights, oxygen consumption, carbon dioxide output, and body fat content were determined in 2 cohorts (n=23, n=24) of offspring. Food intakes and weight changes in response to 3 different diets (regular chow, purified diet, purified high fat diet) were examined in another cohort (n=24) from postnatal days 72 to 116. RESULTS: Litter weights showed a significant linear decrease as a function of toluene dose. Offspring exposed to the 16,000 ppm toluene dose displayed statistically lower energy expenditures than control rats. Male rats exposed to 8000 or 16,000 ppm toluene had significantly greater percentage of body fat as well as total body fat than the other groups. Toluene also significantly suppressed weight gain over the time chow was consumed compared to the 0 ppm control group. Finally there were trends for a main effect of toluene dose on food intake during chow and during high fat diet consumption, with rats in the 12,000 ppm group consuming more than the 0 ppm group on both diets. DISCUSSION: These data suggest that, in addition to other previously documented abnormalities in neurological development and behavior, the physiological regulation of metabolism and body composition in males as well as food intake and weight gain in both sexes may be altered by prenatal exposure to toluene.     

Effects of dietary dehydroepiandrosterone on food intake and body weight in rats with medial hypothalamic knife cuts

Dehydroepiandrosterone (DHEA) is a steroid which has been reported to have anti-obesity effects when added to the diets of rats and mice. In this report, rats made hyperphagic with medial hypothalamic knife cuts were placed on a diet containing 0.45% DHEA or a control diet. Knife cut rats on the control diet ate more food and gained more weight than sham-operated rats on the control diet. In contrast, knife cut rats fed the DHEA diet weighed the same as shams on the DHEA diet and were only observed to be hyperphagic on one of eight 24 hour measurements taken during a five week period. Dietary DHEA reduced food intake and body weight of both knife cut and sham-operated rats, though the effects were smaller in shams. As these effects of DHEA were reminiscent of the effects of dietary quinine adulteration on intake by knife cut rats, a second experiment measured the food intake of unoperated rats when given a choice between a control high-fat diet and one adulterated with various concentrations of DHEA. Even at a concentration of 0.05%, rats clearly identified and avoided the DHEA-adulterated diet. While these results do not rule out effects of DHEA on metabolic rate or lipogenesis, they do indicate that the unpalatability of DHEA-adulterated diets may be a contributing factor in the observed effects on food intake and body weight.     

Long term effects of quinine on food intake and body weight in the rat

Adulteration of a chow diet with 0.75% quinine sulfate produces a short-lived decrement in food intake in both ad lib-fed and previously food-restricted adult female rats. In contrast, quinine produces a long-lasting depression in body weight; ad lib access to quinine-treated chow results in a plateauing of body weight at a lower level until quinine is removed from the diet, despite recovery of food intake.     

Dietary influences on the acute effects of anorectic drugs

The effects of acute administration of d-amphetamine sulfate (0.0, 0.5, 1.0 and 2.0 mg/kg) and dl-fenfluramine hydrochloride (0.0, 1.5, 3.0 and 6.0 mg/kg) on food intake were examined in male Sprague-Dawley rats fed either a high-carbohydrate diet (carbohydrate equaled 65% of total calories) or a high-fat diet (fat equaled 65% of total calories). Animals were given ad lib access to the diets throughout the experiment. Drug injections were given at 0900 on experimental days and food intakes were measured at 1, 3 and 6 h postinjection. Amphetamine led to dose-related decreases in food intake for animals on both diets. The effects of amphetamine were most noticeable at 1 and 3 h postinjection. No differences in amphetamine's effects on food intake were found as a function of diet. Fenfluramine injections also led to dose-related reductions in food intake for animals in both dietary conditions. In contrast to amphetamine, however, fenfluramine led to greater reductions in food intake for rats fed the high-fat diet than for rats fed the high-carbohydrate diet. These data demonstrate that dietary variables must be considered when evaluating the anorectic actions of psychopharmacological agents.     

MSG intake suppresses weight gain, fat deposition, and plasma leptin levels in male Sprague-Dawley rats

Monosodium l-glutamate (MSG), an umami taste substance, may be a key molecule coupled to a food intake signaling pathway, possibly mediated through a specific l-glutamate (GLU) sensing mechanism in the gastrointestinal tract. Here we investigated the effect of the spontaneous ingestion of a 1% MSG solution and water on food intake and body weight in male Sprague-Dawley rats fed diets of varying caloric density, fat and carbohydrate contents. Fat mass and lean mass in the abdomen, blood pressure, and several blood metabolic markers were also measured. Rats given free access to MSG and water showed a high preference (93-97%) for the MSG solution, regardless of the diet they consumed. Rats ingesting MSG had a significantly smaller weight gain, reduced abdominal fat mass, and lower plasma leptin levels, compared to rats ingesting water alone. Naso-anal length, lean mass, food and energy intakes, blood pressure, blood glucose, and plasma levels of insulin, triglyceride, total cholesterol, albumin, and GLU were not influenced by the ingestion of the MSG solution. These same effects were observed in a study of adult rats. Together, these results suggest that MSG ingestion reduces weight gain, body fat mass, and plasma leptin levels. Moreover, these changes are likely to be mediated by increased energy expenditure, not reduced energy intake or delayed development. Conceivably, these effects of MSG might be mediated via gut GLU receptors functionally linked to afferent branches of the vagus nerve in the gut, or the afferent sensory nerves in the oral cavity.     

Effects of CB(1) and CRF(1) receptor antagonists on binge-like eating in rats with limited access to a sweet fat diet: Lack of withdrawal-like responses

Positive reinforcement (e.g., appetitive, rewarding properties) has often been hypothesized to maintain excessive intake of palatable foods. Recently, rats receiving intermittent access to high sucrose diets showed binge-like intake with withdrawal-like signs upon cessation of access, suggesting negative reinforcement mechanisms contribute as well. Whether intermittent access to high fat diets also produces withdrawal-like syndromes is controversial. The present study therefore tested the hypothesis that binge-like eating and withdrawal-like anxiety would arise in a novel model of binge eating based on daily 10-min access to a sweet fat diet (35% fat kcal, 31% sucrose kcal). Within 2-3weeks, female Wistar rats developed binge-like intake comparable to levels seen previously for high sucrose diets (~40% of daily caloric intake within 10min) plus excess weight gain and adiposity, but absent increased anxiety-like behavior during elevated plus-maze or defensive withdrawal tests after diet withdrawal. Binge-like intake was unaffected by pretreatment with the corticotropin-releasing factor type 1 (CRF(1)) receptor antagonist R121919, and corticosterone responses to restraint stress did not differ between sweet-fat binge rats and chow-fed controls. In contrast, pretreatment with the cannabinoid type 1 (CB(1)) receptor antagonist SR147778 dose-dependently reduced binge-like intake, albeit less effectively than in ad lib chow or sweet fat controls. A priming dose of the sweet fat diet did not precipitate increased anxiety-like behavior, but rather increased plus-maze locomotor activity. The results suggest that CB(1)-dependent positive reinforcement rather than CRF(1)-dependent negative reinforcement mechanisms predominantly maintain excessive intake in this limited access model of sweet-fat diet binges.     

Somatic, metabolic and endocrine correlates of set point recovery in food-restricted and ad lib-fed weanling rats with dorsomedial hypothalamic lesions

Male Sprague-Dawley rats received either electrolytic lesions in the dorsomedial hypothalamic nuclei (DMNL rats) or sham-operations (CON), and were fed lab chow ad lib for 41 post-operative (POP) days. Subsequently one lesioned (DNML-AL) and one control group (CON-AL) continued to receive lab chow ad lib until the end of the experiment (POP day 78). A second lesioned (DMNL-RE) and control group (CON-RE) were given 80% of the amount of food eaten by their ad lib-fed counterparts for 28 days. At this time several rats from each group were killed. The remaining animals were then given lab chow ad lib for nine days and then also killed. Both DMNL-RE and CON-RE recovered their lowered body weight, food intake and feeding efficiency and showed the same pattern and relative magnitude as their ad lib-fed counterparts. Similarly, carcass lipid, epididymal fat pad lipid, incorporation of glucose-U-C14 into fat pad saponifiable lipid, total lipid, total glycogen (DPM/protein), liver protein, incorporation of glucose into liver CO2 and concentrations of plasma glucose, glycerol, triglycerides and free fatty acids normalized on refeeding to the same extent and in the same pattern in DMNL-RE as in CON-RE. In contrast to previous studies, plasma insulin was lower in DMNL-AL than in CON-AL but DMNL-RE and CON-RE had similar levels on refeeding. Also on refeeding, both DMNL-RE and CON-RE showed the same enhanced glucose incorporation into liver total lipid. The data show that DMNL rats, although smaller in size and hypophagic in absolute terms, recovered lost body weight--at least under our relative mild reduction of 80% of their ad lib-fed controls--with the same competence and in the same time interval as sham-operated controls. It is quite possible that a more severe restriction of body weight would have uncovered some deficits in DMNL rats, however. Under the constraints of the present experimental arrangement, the data strengthen previous evidence for the existence in DMNL rats of an "organismic" set point that makes for a "scaled-down" but homeostatically normal animal.