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.     

Inhibition of food deprivation induced hypovolemia by saline consumption in rats

Food deprivation hypovolemia has been observed in a variety of mesic and desert adapted rodents. Xeric adapted rodent species appear to lose intravascular volume in proportion with body weight loss during food restriction, while mesically adapted rodent species lose intravascular volume at a rate much in excess to body weight loss. The laboratory rat was chosen as a representative mesically adapted rodent species for the purpose of investigating this phenomenon. Acute isotonic saline stomach loads had no appreciable influence upon intravascular volume reparation induced by either 2 or 4 days of food deprivation. Free and forced choice saline solutions presented during starvation were noted to significantly inhibit hypovolemia, however, there was no evidence for reparation of carcass water losses. It is suggested that the availability of only water during fasting results in the premature termination of drinking due to cellular over-hydration. When water and a source of sodium are available the food deprived rat can more adequately maintain ad lib intravascular volume. There is presently no explanation for the absence of repaired carcass water.     

Overcompensation of food intake following brief periods of food restriction

Four adult female Sprague-Dawley rats, maintained on an ad lib feeding schedule were deprived for either 0, 0.5, 1, 2, 4, 6, or 8 hours during the dark phase of the day-night cycle. It was found that the latency to initiate the first meal following the deprivation was independent of the previous deprivation interval. The animals were found to overcompensate for the periods without food by eating a large initial meal that increased proportionately in size with the duration of food restriction. Furthermore, the animals continued to overeat throughout the day. This deprivation-induced overeating by the animals resulted in an overcompensation in total food consumption that was 21–56% greater than on control days. The role of food intake as a regulator of body weight is discussed.     

Effects of mild food deprivation on the estrous cycle of rats

It has long been known that severe food deprivation disrupts the estrous cycle. One of the main problems with behavioral tasks that use food for reinforcement is the requirement that the animal be food deprived. This manipulation could be problematic in studies using female animals, since it may interfere with the estrous cycle of the animals. The purpose of the present study was to investigate: (1) the effect of mild food deprivation on four different strains of rats, (2) factors in the food deprivation procedure that could affect the estrous cycle, and (3) the possible effect of enriched diets during food deprivation on the estrous cycle. A comparison of the estrous cycle in four different rat strains revealed differences in the reliability of the estrous cycle even before the onset of food deprivation. Fischer, Long-Evans, and Sprague-Dawley rats all showed reliable cycle patterns. This was not the case for Brown Norway rats. During food deprivation, the cycle of the Fischer rats was disrupted, whereas the Long-Evans and Sprague-Dawley animals continued to cycle. Both the rate of weight loss and the percent of ad libitum body weight were related to cessation of the estrous cycle. However, enriching an animal's diet with sugar or oil additives delayed the disruption of the estrous cycle. Additionally, animals resumed cycling when returned to ad libitum weight levels. The present findings suggest that when animals need to be food deprived, preference should be given to using Long-Evans or Sprague-Dawley rats. If Fischer rats must be used, they should not be deprived below 90-95% of their ad libitum body weight. Strategies for future food deprivation studies are discussed, as well as a comparison of the effects of mild and severe food deprivation.     

Body mass loss during adaptation to short winter-like days increases food foraging, but not food hoarding

Siberian hamsters markedly reduce their body/lipid mass (∼ 20-45%) in short ‘winter-like’ days (SD). Decreases in body/lipid mass associated with food deprivation or lipectomy result in increases in foraging and food hoarding. When at their SD-induced body/lipid mass nadir, food hoarding is not increased despite their decreases in body/lipid mass, but hoarding was not tested during the dynamic period of body/lipid mass loss (first 5-6 weeks of SDs). Therefore, we tested for changes in foraging/hoarding during this initial period in Siberian hamsters housed in a simulated burrow with a wheel running-based foraging system and exposed to either long ‘summer-like’ days (LD) or SDs. Two foraging effort conditions were used: 10 Revolutions/Pellet (pellet delivered after running 10 revolutions) and a Free Wheel/Free Food condition (wheel available, food pellets non-contingently available). Regardless of the foraging condition, body mass was significantly reduced across 8 weeks of SDs (∼ 15%). Foraging increased after 7 weeks in SDs, but food hoarding did not increase compared to LDs. Instead food hoarding significantly decreased in SDs at Weeks 2-5 compared with Week 0 values, with the 10 Revolutions/Pellet foraging group returning to LD levels thereafter and the Free Wheel/Free Food group remaining reduced from Weeks 2-7. Collectively, we found that SDs decreased body mass, increased foraging after 7 weeks, and increased food hoarding, but only after an initial decrease and not above that seen in LDs. These data suggest that SD-induced body/lipid mass losses do not engender similar behavioral responses as seen with food deprivation or lipectomy.     

Influence of food and water availability on undirected singing and energetic status in adult male zebra finches (Taeniopygia guttata).

The songs of adult male zebra finches are termed "directed" and "undirected," depending on the social context in which they occur. Females elicit directed song, whereas undirected song is not addressed to a particular conspecific and even occurs at high levels in social isolation. We tested the hypothesis that the production of undirected song is more sensitive to a brief period of food deprivation than a comparable period of water deprivation. The hypothesis was based on prior findings suggesting that song production is energetically expensive and that food deprivation constitutes a more serious energetic challenge to zebra finches than does water deprivation. Two days of food or water deprivation were imposed on several groups of birds that provided song production data and a variety of energetic measures; normative data obtained in a baseline period when food and water were available ad libitum provided a standard for comparison. Singing, which occurred exclusively in the light phase of the day, was reduced at the onset of food deprivation, ceased completely within 4 h, and did not occur at all on the second day. When water was removed, the birds showed a slower and less substantial reduction in daily song production across the 2 days of deprivation. Energetic measures indicated that food deprivation was a greater energetic challenge than water deprivation. Our results demonstrate that undirected song in zebra finches is sensitive to nonsocial environmental factors that pose an energetic challenge and raise new questions about how birds calibrate their level of song production to the availability of nutrients in the environment.     

Weight, corticosterone and glucose: changes with time of day after food deprivation

The effects of constant food deprivation, terminated at different times of day were examined with respect to percent body weight loss (%BWL), plasma corticosterone (PC) and plasma glucose (PG). A 19-hour food deprivation paradigm schedule staggered around varying times of the day-night cycle was used. Patterns of %BWL related to nocturnal lipogenesis and diurnal lipolysis showed the greatest loss (10%) occurring at 0700 hr, while in evening hours, there was an increasing pattern of weight loss, with the greatest amount (7%) occurring at 2200 hr. A pattern suggestive of neuroregulatory cycles of glucocorticoid release was evident for PC levels; maximum levels for PC (23.2 micrograms%) were reported at 0700 hr and at 1900 hr (16.6 micrograms%). Similar patterns were also noted in PG levels, with respective maximum levels of 138.0 mg% and 125.8 mg% occurring at 0700 hr and 1900 hr. These results indicate that the time of day that a deprivation schedule is initiated and terminated is an important consideration due to the impact of circadian photoperiodism. Time of day should be an essential consideration when utilizing deprivation paradigms.     

Dietary self-selection of golden hamsters in response to acute food deprivation and chronic food restriction

Adult male golden hamsters were maintained on either Purine Rat Chow (Chow diet) or a self-selection diet consisting of high-protein chow, pure fat, and pure carbohydrate (Choice diet). In Experiment 1, animals were deprived of food for single periods of up to 48 hr. Animals on the Chow diet did not increase intake at any time after deprivation; animals on the Choice diet selectively increased their consumption of fat-derived calories and increased their total caloric intake during the first 6 hr of refeeding, but not thereafter. The nature of the diet did not influence the rate at which animals regained weight following deprivation. In Experiment 2, hamsters were placed on food-restriction schedules (access to food either for 1 hr/day only or on alternate days only) until they lost 20% of starting body weight. Chow-fed animals demonstrated little or no change in food intake either during or after food restriction. Hamsters on the Choice diet consumed more calories and lost weight more slowly than did chow-fed animals during 1-hr/day feeding; intake of fat-derived calories was elevated during restriction. Choice hamsters increased total caloric intake only towards the end of the alternate-days restriction schedule. Choice hamsters were hyperphagic following both types of food-restriction schedules, but no increased preference for fat-derived calories was observed. Factors influencing food consumption of hamsters in response to deprivation and restriction are discussed.     

Effects of thalamic taste nuclei lesions on the ingestion of sapid solutions and schedule induced and schedule dependent behavior

Rats were reduced to 80 percent body weight and were exposed to an FI-1 min food reinforcement schedule for 30 min daily until lever presses, licks, and water consumption stabilized for at least 10 days. Bilateral lesions were then made in the thalamic taste nucleus of all animals. Animals were tested for 50 days following the lesions at 80 percent body weight, were permitted to recover body weight by increasing food rations, and were tested for an additional 30 days under ad lib feeding. Animals were then subjected to the following tests: food consumption following food deprivation, drinking following water deprivation, salt arousal of drinking, and drinking of 7°C water following water deprivation. In addition, consumption of 6.85% sucrose, 25% sucrose, 8% glucose, 21% glucose, and 0.125% Na saccharin on a FI-1 min food reinforcement schedule and under home cage conditions were measured. On the basis of these data and lesion locus the 8 animals were divided into 2 groups, bilaterally symmetrical experimentals and asymmetrical controls. Although only transient effects were observed in licking, water consumption, and lever pressing, animals with bilateral symmetrical lesions of the medial ventral thalamic nuclei displayed relatively permanent deficits in their responses to various taste stimuli and the salt arousal of drinking. The effects of these lesions are evaluated and discussed in terms of the lateral hypothalamic invovlement in schedule induced and schedule dependent behavior.     

Effects of food deprivation and metabolic fuel utilization on food hoarding by jirds (Meriones shawi).

Food hoarding plays an important role in the energetic repertoire of a variety of mammalian species. Both food hoarding and food intake have been examined in rodents using several energetic challenges including food deprivation, treatment with metabolic fuel blockers, and enhancement of fuel storage. In the present experiment, we examined food hoarding by female jirds (Meriones shawi), a desert rodent species occupying the arid steppes and desert regions of Egypt. Jirds are prodigious hoarders in the field; however, virtually nothing is known about their hoarding within controlled laboratory settings. In the present study, the effects of food deprivation as well as alterations in metabolic fuel utilization (i.e., 2-deoxy-D-glucose and isophane insulin) on food hoarding and food intake were tested in female jirds using a simulated burrow system. Jirds decreased body mass and increased food consumption following either 32 or 56-h food deprivation. Food hoarding, however, was virtually abolished after food deprivation and treatment with 2-DG. In contrast, isophane insulin treatment had no effect on food consumption or hoarding in this species. Taken together, the present results suggest that total body mass (fat), rather than short-term metabolic fuel utilization, regulates both food consumption and hoarding in female jirds. In addition, these results provide a novel set of appetitive responses to these energetic challenges in small mammals.     

Response to acute food deprivation in OLETF rats lacking CCK-A receptors

Otsuka Long-Evans Tokushima Fatty (OLETF) rats lacking cholecystokinin (CCK)-A receptors are hyperphagic and obese, and exhibit deficits in meal size control and in neuropeptide Y (NPY) gene expression in the dorsomedial hypothalamus (DMH). The present study was intended to determine whether these deficits would affect OLETF rat's response to an acute 24-h period of food deprivation. OLETF rats lost more body weight in response to deprivation but recovered their weight more quickly during refeeding than did lean Long-Evans Tokushima Otsuka (LETO) rats. Food deprivation decreased plasma glucose and leptin levels to a similar degree in both strains. Both groups increased intake during refeeding but the magnitude of increase was significantly greater in OLETF rats. Deprivation resulted in a significant elevation in arcuate NPY gene expression (approximately 47%) in LETO rats but only produced a small nonsignificant increase in the already decreased level of expression in OLETF rats (approximately 24%, P>.05). DMH NPY gene expression was not changed by deprivation in either OLETF or LETO rats. Although paraventricular corticotropin-releasing factor (CRF) expression was decreased by deprivation in LETO rats, CRF expression was not affected in OLETF rats. Together, these data suggested that OLETF rats lacking CCK-A receptors are not only capable of increasing their food intake in response to food deprivation, but also exhibit differential sensitivity to the effects of deprivation during both the food deprivation and refeeding periods.     

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.     

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.     

Behavioral and autonomic temperature regulation in competition with food intake and water balance of pigeons

Four adult pigeons were conditioned to adjust to a preferred ambient temperature and to receive food or water by instrumental responses. The experiments were performed in a Skinner-box under heat load conditions. Each session lasted 1 h. The birds were deprived of food and water for several days before the actual experiments with the exception of the control tests.The exposure to different heat loads (50°, 55° and 60° C) effected both an increase in the responses for cold reward and a rise in respiratory evaporation (panting). The combined effort of behavioral and autonomous responses resulted in constant body temperature (42° C) under the three heat conditions (Fig. 1).The food deprivation effected a preference of instrumental response for feeding and a negligence of behavioral temperature regulation, whereby a slight hyperthermia resulted in the first part of heat exposure (55° C, Fig. 2).Water deprivation reduced the rate of respiration and simultaneously forced the response for cold reward, through which the deep body temperature was adjusted to the control level of 42° C (Fig. 3).Intragastric infusion of 20 ml NaCl (0.8 mol) half an hour before starting heat load (55° C) produced the same result as water deprivation. Whereas infusion of isoosmotic KCl solution did not produce any deviation from the control tests (Fig. 4).The results show competition between the conditioned thermal behaviour and the motivation of feeding or drinking in animals which may permit to compare the conditioned thermal behaviour with the natural kinds of behavioral temperature regulation. The non-appearance of hyperthermia under conditions of water deprivation and NaCl loading may indicate that the animals are able to use the autonomous and the behavioral types of heat defence responses to a greater or lesser extent as circumstances demand. This question seems to be of great interest and is fully discussed here.     

Effects of basolateral amygdaloid lesions on schedule induced and schedule dependent behavior.

Rats were reduced to 80% body weight and were exposed to an FI-1 min food reinforcement schedule for 30 min daily until lever presses, licks, and water consumption stabilized for at least 10 days. Bilateral lesions were then made in the basolateral amygdala of all animals. Animals were tested for 40 days following the lesions at 80% body weight, were permitted to recover body weight by increasing food rations, and were tested for an additional 15 days under ad lib feeding. Animals were then subjected to the following tests: food consumption following food deprivation, drinking following water deprivation, and salt arousal of drinking. In addition, consumption of 6.85% sucrose, 25% sucrose, 8% glucose, 21% glucose, and 0.125% Na saccharin on a FI-1 min food reinforcement schedule and under home cage conditions were measured. On the basis of these data and lesion locus the 8 animals were divided into 2 groups, bilaterally symmetrical experimentals and asymmetrical controls. Although no effects were observed in licking, water consumption, and lever pressing, animals with bilateral symmetrical lesions of the basolateral amygdala displayed relatively permanent deficits in their responses to various taste stimuli. The effects of these lesions are evaluated and discussed in terms of the lateral hypothalamic involvement in schedule induced and schedule dependent behavior.     

Influence of food and water deprivation on the behavior of the white rat foraging in a hostile environment

Rats were trained to feed 2 hr per day, the food offered being placed at 16 m from a warm refuge and the ambient temperature being - 15 degrees C. They were food deprived for 0, 12, 22, 46, 70 and 94 hr prior to the six feeding sessions. Speed of feeding and meal duration were not influenced by food deprivation. The amount eaten, the number of meals, the time spent at the feeder, the speed of running to the feeder and the number of foraging rats increased from 0 hr fast to 22 hr then plateaued for the 46, 70 and 96 hr fasts. The same experiment was carried out after water deprivation for 0, 12, 22, 46 and 70 hr. Rats could find, at -15 degrees C, water kept at 30-40 degrees C and at 16 m from their warm refuge. The speed of running to water and the rate of drinking were not influenced by water deprivation. The amount drunk, drinking-bout duration, the number of drinking-bouts, total drinking time and the number of rats drinking increased monotonically from 0 to 70 hr deprivation. Two main conclusions are drawn from these data: (1) in the rat, up to 70 hr deprivation, the motivation to feed seems to be stronger than the motivation to drink; (2) to satisfy hunger or thirst, the nervous system uses several different motor subsystems of behavior.     

Anorexia, food deprivation and hibernation

Two experiments examined the relationship between food eaten and the lenghts of bouts of continuous hibernation of golden-mantled ground squirrels, Citellus lateralis, kept at 5 ± 4°C. The first experiment showed that food deprivation at the start of the hibernation season increased the hibernation bout lengths compared to a control group given food ad lib. The second experiment showed that animals without food at the end of the hibernating season decreased bout lengths to near to 4 days; they continued to hibernated in this manner until refed at which time hibernation soon stopped altogether. Factors other than food intake contributed toward determining bout lengths since progressive changes in durations of continuous hibernation occurred at different times of year even in food deprived animals. It was argued that if high food intakes are incompatible with staying in a torpid state for many days on end, then set points for body weight must necessarily be lowered over the hibernation season.     

Oxytocin inhibits food and fluid intake in rats

Increasing evidence indirectly suggests a role for oxytocinergic neurons in the control of ingestive behaviors. The present study was aimed at directly investigating a possible effect of oxytocin on food and water intake in rats. Oxytocin, whether administered intracerebroventricularly (ICV) (1-10 micrograms/rat) or intraperitoneally (IP) (375-3,000 micrograms/kg) dose dependently inhibited food intake in freely feeding animals; in schedule-fed animals fasting for 21 h, oxytocin not only reduced food intake but also reduced the time spent eating and increased the latency to first meal. On the other hand, oxytocin antagonist d(CH2)5Tyr(Me)-[Orn8]-vasotocin, ICV injected at the dose of 10 micrograms/rat, increased food intake and time spent eating and reduced the latency to first meal; moreover, it completely prevented the effect of oxytocin. Water intake was studied both in freely drinking animals and in three different models of thirst (water deprivation, hypertonic saline administration, angiotensin II injection). In all cases, oxytocin dose dependently inhibited water intake, in a dose range of 0.1-10 micrograms/rat (ICV) or 93-750 micrograms/kg (IP). In the water deprivation model, ICV pretreatment with d(CH2)5Tyr(Me)-[Orn8]-vasotocin completely prevented the antidipsogenic effect of oxytocin. In conclusion, these data show that oxytocin directly inhibits food and water intake in rats, the effect being specifically mediated by brain oxytocin receptors. This may support the idea that the brain oxytocinergic system plays an important role in the regulation of ingestive behaviors.     

Effect of age, food deprivation and stress on gastric erosions in the rat

Two experiments were conducted in which rats were subjected to food deprivation and/or cold-restraint stress. In Experiment 1, 40- and 570-day old rats exhibited a significant degree of glandular gastric erosion due to the stress and to the deprivation. Both of these were attributable to the single condition wherein deprivation and stress were combined. No effect involving age was significant. In Experiment 2, 22-day old weanlings exposed to the same conditions evinced a significant glandular erosion effect of the deprivation, but neither the stress nor the interaction effects were significant. It was concluded that 3 hr of cold restraint in the sated mature rat has a relatively minor effect on the stomach. Forty-eight hours of food deprivation, also ineffective by itself in such animals, renders the stomach vulnerable to the effects of stress. In the weanling, in contrast, deprivation alone can cause glandular erosion but its potentiating effect is lacking. With respect to ruminal lesions, it was hypothesized that time without food rather than initial body weight or nutritional deficit is the critical variable.     

A water deprivation test for the differentiation of polyuric disorders in birds

A water deprivation test was developed for the differentiation of polyuric disorders in birds using the racing pigeon as a model. For a period of 3 days of food and water deprivation, urine and plasma osmolalities and body weight of 40 clinically healthy racing pigeons were monitored. Reference values for urine osmolality after 40 hours of food deprivation were 79 to 480 mOsmol/kg. After 64 hours of food deprivation and 24 hours of water deprivation these values were 450 to 875 mOsmol/kg. No significant rise in urine osmolality was seen after the first 24 hours of water deprivation. It is concluded that an urine osmolality greater than 450 mOsmol/kg is indicative of a normal concentrating capacity of the kidney in the pigeon. Data from the literature suggest that these values can be applied to other avian species.