Electroconvulsive shock effects on food and water intake as a function of prior deprivational state

Two experiments, each using approximately 30 male and 30 female hooded rats, examined the effects of electroconvulsive shock (ECS) on water intake as a function of the water deprivation state of the animal and food intake and body weight as a function of food deprivation state. In Experiment 1, half the animals were subjected to water deprivation prior to ECS or sham ECS, and the other half were watered ad lib; in Experiment 2, food deprivation was the pre-ECS manipulation. As predicted, ECS produced a decrease in water intake in the ad lib watered animals but not in the deprived ones. A similar treatment by deprivation interaction was not found for food intake or body weight. In the males, food intake was decreased for one day by the treatment but recovered to a normal level two days following ECS; however, such an effect of ECS on food intake did not occur in the females. Since food and water intake was not differentially affected by ECS and sham ECS in deprived animals, previous cautions regarding ECS effects on motivational states may not be germane to many studies using appetitive conditioning paradigms.     

Strain differences in drinking in inbred mice during ad libitum feeding and food deprivation

Water intakes were measured in 7 mouse strains under 3 conditions of food availability: (a) ad lib feeding, (b) $\text{1}\text{3}\text{-}\text{normal}$ food intake, and (c) total food deprivation. Under ad lib feeding strains were ranked according to magnitude of water intake. These ranks were similar, but not identical, when absolute water intakes (ml) and relative (ml/100 g body wt) water intakes were measured. Statistically reliable, positive correlations were found between food intake and body weight, water intake and food intake, and water intake and body weight. Under the $\text{1}\text{3}\text{-}\text{food}$ condition, mean water intakes decreased significantly from ad lib feeding conditions in the BALB/cJ, A/J and C57BL/6J strains, did not change significantly in the SWR/J, CBA/J and DBA/2J strains and increased (food-deprivation polydipsia) in the C3H/HeJ strains. Results in 2 replications of total food deprivation parallelled those of $\text{1}\text{3}$ normal intake except that in the former condition DBA/2J mice showed a significant decrease in water intake. Food-deprivation polydipsia was seen in some individual SWR/J and CBA/J mice, as well as in the C3H/HeJ strain but was very rare in the other four strains.     

Refeeding after differential severity of deprivation

Forty-eight female rats were randomly assigned in equal numbers to an eight-day 0, 20, 23, 23.5, 46-hour food deprivation schedule, or complete starvation, followed by two weeks of ad lib refeeding. Two of the completely starved subjects died. Due to decreased metabolic need of the animals after weight loss, daily food intake was considered relative to body weight. Water consumption relative to body weight increased by the end of deprivation except for animals unadapted to deprivation. The major findings during refeeding were: (a) post-starvation anorexia does not occur after any form of starvation (scheduled or complete) when body weight is considered; (b) instead of being highest on the first day of refeeding, food consumption slowly increases to a maximum and then returns to ad lib control level; (c) the more severe the deprivation, the longer time for food consumption to reach its maximum and return to control levels; (d) the more severe the deprivation, the greater the maximal food consumption.     

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.     

Interrelationships among activity,food intake and weight gain in genetically obese and lean Zucker rats

In Experiment 1, food deprivation resulting in a 30% reduction in body weight produced significant increases in wheel running in both obese and lean female Zucker rats. In Experiment 2, a new technique, food contingent activity (FR, VI), dramatically increased wheel running in both obese and lean female Zucker rats. This increase in activity was achieved primarily during the dark period. Regardless of changes in activity levels, food intake and body weight gain remained similar to controls. When food was again available ad lib, activity levels rapidly decreased for obese but not lean rats. These results indicate that behavioral interventions alone are not sufficient to correct the obesity of the genetically obese rat.     

Efficiency of food utilization during body weight gain in dormice (Glis glis)

During spontaneous body weight gain in dormice, Glis glis, progressive increases in the efficiency of food utilization as defined by weight gain (g)/food intake (g), and parallel increases in mean daily food intake were observed. Towards the end of the weight gain period, there was an abrupt drop in feeding efficiency with no significant change in food intake even when the latter was expressed relative to an index of each animal's “metabolic mass” (body weight_kg^0.62). Animals whose body weight increases followed a return to ad lib feeding after prolonged food restriction showed marked decreases in feeding efficiency from initially high values which were independent of changes in food intake. These results are discussed in relation to the sliding set point concept of body weight regulation in hibernators.     

Diet-induced thermogenesis and cumulative food intake curves as a function of familiarity with food and dietary restraint in humans.

Cumulative food intake curves and diet-induced thermogenesis were recorded in women during four-course solid-food lunches, consisting of familiar and unfamiliar food, offered in ad lib or restricted portions, in order to assess a possible relation between eating behaviour on the one hand and a reflection of internal processes and subject characteristics on the other. The subjects were characterized as normal weight restrained, normal weight unrestrained, and overweight restrained. A negative relation was found between degree of restraint and deceleration of the cumulative food intake curve during the ad lib courses of any menu, and between degree of restraint and diet-induced thermogenesis (p less than 0.001). Consequently, a positive relation was found between deceleration of the cumulative food intake curves during the ad lib courses of any menu and diet-induced thermogenesis (p less than 0.001). Diet-induced thermogenesis during the first serving of a meal consisting of unfamiliar food was significantly higher in all groups than during the other two times, when meals consisting of more familiar food were served (+0.98%; 0.71%, p less than 0.05).     

Effects of subdiaphragmatic vagotomy on schedule induced drinking and schedule dependent lever pressing

Fourteen male albino rats reduced in body weight were exposed to a daily 1 hr FI-1 min schedule of food reinforcement. When schedule induced licking and drinking and schedule dependent lever pressing stabilized, seven animals were subjected to bilateral subdiaphragmatic vagus nerve transections and the other seven animals were subjected to sham operations. Changes in licking, drinking, and lever pressing were assessed when animals were reduced to 80% of their initial body weight by partial food deprivation and when body weights recovered after the animals were returned to conditions of ad lib feeding. Results indicate that vagotomy produces a significant decrease in schedule induced licking and drinking when animals are at reduced body weight. When vagotomized rats are allowed to recover body weight due to ad lib feeding, lever presses decrease but licking and drinking are not further reduced. The sham operation had no appreciable effects at reduced body weight. When allowed to recover body weight sham animals exhibited significant decreases in licking, drinking, and lever pressing. In addition, the rate of body weight gain and home cage food and water consumption and water consumed in response to hypertonic saline injections were reduced in vagotomized animals when allowed to feed ad lib. Results are discussed in terms of vagal afferent activity from the viscera to the lateral hypothalamus associated with food deprivation and body weight reduction and the maintenance of adjunctive behavior.     

Hypothalamic hyperphagia despite imposed diurnal or nocturnal feeding and drinking rhythms.

Rats normally do most of their eating at night. When ad lib fed rats are made hyperphagic with lesions or parasagittal hypothalamic knife cuts the increases in eating occur primarily during the day. This suggests that a disruption of circadian rhythms may mediate the overeating. However, when knife cut rats were food and water deprived all day excessive eating occurred at night. Similarly, when they were deprived all night overeating occurred during the day. Under both conditions od deprivation the food intakes and rapid weight gains of the ad lib fed knife cut group were defended. It was concluded that: (1) in hypothalamic hyperphagia either the excessive food intake or the excessive weight gain is defended when food and water are available only half of each day, and (2) disruption of nocturnal feeding and drinking rhythms is not the cause of hypothalamic hyperhagia.     

Eelectrically induced and normal feeding: different controls in the dormouse.

In edible dormice, Glis glis, cyclic infradian variations in body weight, normal ad lib food intake, and thresholds for lateral hypothalamic electrically induced feeding were compared over a 4 month period. At times when normal food intake was high, it was more difficult to obtain electrically induced feeding. No clear relationship was found between body weight and thresholds for induced feeding. These results suggest that the two types of feeding are not controlled in a similar way, and that negative feedback from the consequences of normal ad lib ingestion subsequently depresses electrically induced feeding but not normal feeding.     

Hoarding of food and non-food items in blind, anosmic and intact albino rats

Hoarding was studied in anosmic, blind, and sham-operated rats. It was found that: (1) blindness had little effect on hoarding, while anosmia led to increased hoarding in both ad lib and food-deprived conditions; (2) during ad lib feeding, blind and sham-operated animals showed a preference for wooden blocks over food pellets. During deprivation the reverse occurred. The anosmic animals did not display any consistent preference during ad lib feeding, but behaved like the other groups during deprivation; and (3) anosmic rats showed an initial increase in both latency to emerge from the home cage and time spent in the cage. It is concluded that (1) neither olfactory nor visual cues are necessary to elicit any of the behaviors which are involved in hoarding; (2) the increased hoarding of anosmic rats may be related to increased shyness; and (3) the preference for wooden blocks over food pellets during ad lib feeding may be related to gnawing.     

Effect of Water Deprivation on Eating Patterns of Lactating Cows Fed Grass and Corn Pellets Ad Lib

The present study investigated the effect of 48 h of water deprivation on eating behavior of 12 lactating cows fed grass and corn pellets ad lib. Water deprivation reduced grass and corn pellet intake significantly, with corn pellet intake decreasing earlier than grass intake. The reduction of feed intake was entirely due to a reduction of meal size for both grass and corn-pellet meals. The size of the first meal of the water deprivation period was already reduced by about 30%. Grass-meal frequency increased, whereas corn-pellet meal frequency decreased during water deprivation. Water deprivation also decreased live weight and milk yield by about 12 and 30%, respectively. All parameters returned to baseline values with rehydration. With ad lib access to feed and water, 77% of drafts occurred in relation to meals, but the number of meals clearly exceeded the number of drafts. The results demonstrate that water deprivation rapidly leads to premature meal termination. This is in line with the assumption that an enhanced prandial increase in ruminal fluid osmolality contributes to dehydration-induced hypophagia. Yet, further studies are necessary to prove this assumption and to better understand the complex relationships between eating and drinking in ruminants.     

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.     

Circadian patterning of feeding,drinking and activity during diurnal food access in rats

Using an “ecologically” relevant approach, the present study investigated (1) the association between feeding and drinking patterns and their circadian organization and (2) changes in general activity (or life-style), during ad lib conditions (fa:LD) and in a situation where access to food was restricted to the light phase (fa:L). Rats were housed in large outcages with nest boxes. Feeding, drinking, activity, outcage and nest occupation were recorded automatically throughout the day-night cycle. Access to food was restricted by a sliding door situated in front of the food hopper. Under ad lib conditions rats were mainly nocturnal, eating 94% and drinking 95% of their daily intakes at night. The patterns of food and water intake were similar, showing a bimodal distribution over the dark phase. During fa:L rats showed an initial large peak in feeding with lights on, followed by a long pause. Thereafter, feeding activity was variable but remained at a low level. The nocturnal drinking pattern persisted. However, 17.5% of daily water intake was meal-associated, compared with 71% during ad lib. Diurnal activity was associated with feeding and nocturnal activity with drinking. Nocturnal outcage and nest occupation patterns were not shifted to the light phase. The experiment demonstrates that rats on an fa:L schedule reduce food and water intake, and body weight, while still retaining circadian characteristics in the temporal distribution of drinking, activity, outcage and nest occupation. Further, although feeding and drinking may be causally related they need not occur in close temporal association. The rapidity of re-establishment of the normal feeding pattern, on return to free-feeding, and the close association with drinking under normal conditions, suggest the existence of a single or two coupled oscillators controlling feeding and drinking.     

Some determinants of intake and patterns of feeding in the guinea pig

Regulation of food and water intake was studied in young and adult Guinea pigs by continuously monitoring ad lib feeding and drinking patterns and by examining the response to levels of celluflour dilution that ranged from 20–75%. Meal size and the duration of the intermeal interval were not systematically related to the sizes of preceding meals or interval lengths. Variations in food intake were mediated almost entirely by changes in meal size. This parameter increased during growth, was elevated in the first meal following food deprivation, decreased when water was withheld and increased when water was returned. The probability of drinking within 20 min of eating was 0.80. Celluflour dilution led to a decrease in apparent caloric intake without a proportional decrease in body weight. Regulation of energy balance and meal to meal control of feeding in this monogastric, herbivorous rodent is discussed in relation to the Guinea pig's digestive physiology and ecological niche.     

Body weight regulation in ground squirrels and hypothalamically lesioned rats: slow and sudden set point changes

Golden-mantled ground squirrels. Citellus lateralis, have a near annual cycle in body weight. In the present experiments their weights were temporarily forced off the usual levels either by food deprivation during a phase of weight gain or by offering extra palatable food during a phase of weight loss. When these treatments ceased the weights returned to levels appropriate for that time of year rather than to pretreatment values. Therefore the cycle of body weight in uniform and ad lib conditions reflects an underlying cycle in slowly climbing or sliding set points for body weight. In contrast to fattening ground squirrels, lesioned rats in the dynamic phase of hypothalamic hyperphagia did not compensate well for weight losses incurred during food deprivation. Weight gain during the dynamic phase appears to be roughly proportional to the discrepancy between actual and set weights, the latter being suddenly much elevated by the lesion.     

Refeeding after the late increase in nitrogen excretion during prolonged fasting in the rat.

Recovery of body mass, food intake and body composition was studied in the laboratory rat after the late increase in nitrogen excretion that characterizes prolonged fasting in mammals and birds. The rats lost 43% of their body mass during 13 days of food deprivation. They all regained their prefasting body mass within a shorter period of 11 days of refeeding. These results confirm that the late increase in nitrogen excretion in rats, as in spontaneously fasting birds, is reversible and is a part of the physiological adaptations to long-term food deprivation. Water intake of the rats continuously decreased during fasting, and the animals virtually stopped drinking as protein utilization increased. On refeeding, changes in water intake paralleled those in food intake. The refed rats progressively increased their daily food intake, that was always higher than the prefasting value (8.0-10.4 vs. 6.7% of body mass). The comparison of organ weights between fed and ad lib refed rats of similar body weight indicates that muscle mass was regained earlier than body fat during refeeding. The laboratory rat therefore appears to be a good experimental model to investigate the metabolic and behavioural changes that occur during spontaneous anorexia and refeeding in wild animals.     

The metabolic cost of activity in activity-naive rats

The influence of activity, age, and ration size on the rate of weight loss was determined in three experiments. Activity did not influence the rate of weight loss during starvation or limited feeding but was associated with a temporary reduction in food intake and a sustained depression in body weight in the ad lib condition. The relationship between percent BW loss and activity was identical whether weight loss had been incurred during starvation or limited feeding. In order to account for the identical rates of weight loss in active and non-active rats during food deprivation it was suggested that compensation for the energy dissipated in running could occur at either the behavioral or physiological level. Specific mechanisms for this compensation were considered.     

Effects of two body weight reduction regimens on schedule dependent and schedule induced behavior

Fifteen male hooded rats were divided into three equal groups on the basis of body weights. One group was allowed to eat ad lib and constituted the Control Group. The second group of animals was reduced over 7 days and adjusted to 80 percent of the body weight of the animals in the Control Group for a 23 day period and constituted the Adjusted Group. Animals in the third group were reduced to 80 percent of their own predeprivation body weight over 7 days and were maintained at this constant level for a 23 day period and constituted the Constant Group. The two experimental groups were then allowed to feed ad lib for the remainder of the experiment. Both the Adjusted and the Constant Groups were tested throughout restricted and ad lib eating periods on a FI 1 min food reinforcement generator schedule. Schedule dependent lever pressing, schedule induced licking and drinking, food intake and body weights were recorded for the duration of the experiment. Results demonstrate that schedule induced licking and drinking and schedule dependent lever pressing increased in the Constant Group at reduced body weight. Animals in the Adjusted Group did not change significantly on these measures during the same periods. When animals were returned to ad lib feeding conditions, the Constant Group initially increased body weight at a faster rate, ate significantly more, and exhibited significantly increased schedule induced licking and drinking. These initial differences disappeared later during the same period. The two experimental groups did not attain the expected body weight of the normal Control Group during 78 days of ad lib eating. Apparently, when animals are initially deprived rapidly and maintained at relatively constant body weight reduction, a prolonged body weight deficit occurs even though these same animals eat normal amounts of food.     

Effects of VMH lesions on schedule induced and schedule dependent behaviors

Ten male hooded rats were exposed to an FI 1 min food reinforcement generator schedule at 80% body weight and schedule dependent lever pressing and schedule induced licking and drinking were recorded. When lever pressing, licking, and drinking stabilized the 10 rats were divided into two groups. One group was composed of 4 animals subjected to sham lesion procedures plus one animal with asymmetrical ventromedial hypothalamic (VMH) lesions. The other group was composed of 5 animals with bilateral symmetrical VMH destruction. Results demonstrate that VMH destruction produces a slight transient decrease only in water intake when on schedule at 80% body weight. When animals are returned to ad lib eating and body weight increased and they are returned to the test chamber, the VMH lesion animals display increased licking and drinking. Although VMH lesion animals ate and drank more than controls, they did not eat more in response to food deprivation and did not drink more in response to water deprivation and the intraperitoneal administration of hypertonic saline. The presence or absence of food or water was the determining factor in the overeating or excessive drinking of the VMH lesion animals. Results are discussed in terms of gastrointestinal influences on the hypothalamic mechanisms involved in the production of schedule induced behaviors.