Feeding, activity, and body temperature following 6-hydroxydopamine lesions in diabetes (db/db) mice.

Reductions in central catecholamines produced by intraventricular injections of 6-hydroxydopamine (6-OHDA) cause weight loss and decreased plasma glucose in diabetes (db/db) mice. The present study examined the effects of this treatment in short-term (64-day) and long-term (120-day) survival groups of female diabetes (C57 BL/KsJ-db/db) and lean mice. Phenotypically heterozygotes (db/m) and homozygotes (m/m) were used as controls. Diabetes Ss treated with 6-OHDA decreased food intake, lost weight, and maintained a lower weight than vehicle-treated controls until vehicle-treated Ss began to enter the terminal stages of the syndrome, indicated by a loss of body weight. Diabetes Ss given 6-OHDA lost weight despite reduced body temperatures and activity levels. Blood glucose levels were always lower in 6-OHDA than in ad lib fed vehicle-treated db/db Ss. The 6-OHDA treatment also improved pancreatic islet granulation. Pair feeding vehicle-treated with 6-OHDA-treated db/db Ss did not halt weight gain in the vehicle-treated group. However, measurement of carcass fat indicated similar losses in db/db-6-OHDA Ss and vehicle-treated Ss when the vehicle group was pair-fed with lean controls. Treatment with 6-OHDA produced long-term improvement in the diabetes syndrome, but the decreased body weight of the 6-OHDA-treated diabetes Ss could not be completely accounted for by changes in food intake or energy expenditure. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects on body weight of central 6-hydroxydopamine lesions in obese (ob/ob) and diabetes (db/db) mice.

Obese (ob/ob) and diabetes (db/db) mice are genetic mutants that have been shown to have altered levels of central catecholamines (CAs) as well as syndromes of obesity, hyperphagia, and hyperglycemia. Because the CAs, and particularly norepinephrine (NE), are implicated in the control of feeding, levels of central CAs were experimentally reduced in ob/ob and db/db mice to investigate the role of CAs in these cases of spontaneously occurring obesity. Lesions produced by 6-hydroxydopamine (6-OHDA) were used to produce large depletions of NE and dopamine (DA) in both ob/ob and db/db mice and in lean control Ss of the same background strains. In the db/db but not the ob/ob, central CA depletion was accompanied by a significant and persistent weight loss and by a reduction in plasma glucose levels when compared with vehicle-infused controls. Treatment with the NE uptake blocker desipramine (DI) prior to 6-OHDA infusions attenuated NE but not DA depletion. Diabetes Ss that received DI pretreatment showed a weight loss and decrease in plasma glucose proportional to the amount of NE depletion. Lean Ss that received the 6-OHDA treatments showed only a transient weight loss and no significant change in blood glucose. Abnormalities in central noradrenergic systems may account for part of the obesity syndrome in the diabetes mouse. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Food motivation and body weight levels in hypothalamic hyperphagic rats: A dual lipostat model of hunger and appetite.

Compared the food and water motivations of 26 normal and 29 hyperphagic female Carworth CFE rats using barpressing performance on continuous reinforcement, VI, and fixed-ratio schedules. Under conditions of food or water deprivation, hyperphagic Ss displayed normal barpressing rates for food or water when their body weights were limited to preoperative or control levels but subnormal barpressing rates when they were tested at obese body-weight levels. Under nondeprived conditions, dynamic hyperphagic Ss barpressed more than controls for a palatable milk diet, while obese hyperphagic Ss worked at control levels for this diet. The findings suggest a dual lipostat model of hunger and appetite to explain feeding and body weight regulations in normal and hypothalamic hyperphagic animals. (62 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rats define different body weights depending on palatability and accessibility of their food.

Normal adult Long-Evans rats lived on powdered diets adulterated to contain as much as 1.6% quinine sulfate, on a palatable high-fat diet, or in Skinner boxes with 45-mg Noyes pellets available on FR schedules as high as FR-256. They maintained lower body weights over periods of months in proportion to the percentage of quinine adulteration or the FR. Ss on the high-fat diet overate as much and gained weight as rapidly as Ss recovering from food deprivation, and became moderately obese. Ss having become lean or obese contingent on the palatability or accessibility of their diet defended body weight by eating more in the cold, less when force-fed by gavage, and more to restore weight after food deprivation. Yet on chow they restored and defended body weights typical of Ss whose diet had been confined to commercially prepared chow. Results are inconsistent with motivational models that rigidly distinguish drive from incentive, that treat body weight changes as evidence for failure to regulate energy balance or body weight, or that rely exclusively on deprivation of food or reduction of body weight for definitions of need for calories. Instead, caloric homeostasis in rats may incorporate ecological constraints. (30 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Comparison of ovarian and hypothalamic obesity syndromes in the female rat: Effects of diet palability on food intake and body weight.

Results of 2 experiments with 96 CFE female rats show that both ovariectomy and hypothalamic knife cuts produced hyperphagia and obesity in Ss. The ovarian obesity, however, unlike hypothalamic obesity, was virtually independent of diet palatability. Ovariectomized Ss became obese on quinine-adulterated diets which completely blocked hypothalamic obesity, and they displayed little further weight gain when given a high-fat diet which greatly potentiated hypothalamic obesity. Ovarian and hypothalamic obesity were also found to be additive irrespective of diet condition when both surgical treatments were combined in the same S; that is, ovariectomy increased the food intake and body weight of knife-cut Ss given the quinine or high-fat diet. In contrast to their dissimilar feeding effects, ovariectomy, hypothalamic cuts, and the combined surgeries did not differentially alter the aversion to a 0.01% quinine solution. Results indicate that ovarian obesity and hypothalamic obesity represent 2 different feeding disorders and are mediated by separate neural mechanisms. The functional nature of these disorders is discussed in light of recent body weight set point interpretations. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of early food deprivation on mouse behavior.

Assessed the effects of early food deprivation upon open-field defecation and activity, running-wheel activity, and food-competition behavior using 76 A/J and 73 DBA/2J mice. Experimental Ss were food deprived from Day 18-27 of life for 10 hr/day. Food-deprived Ss defecated more in the open field and were less active in the running wheels. In these measures, strain and sex interacted with treatment. DBA mice which received the deprivation treatment were less competitive than the comparison Ss, but the treatment did not affect competition in the A/J Ss. It is suggested that the severity of the treatment and age when it was administered interfered with normal development of behavior. (21 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of feeding in rats: I. Ingestive and behavioral responses to oral infusions.

Reports on 3 experiments with Charles River rat pups. When milk infusions were made through oral cannulas in the front of their mouths, 1–20 day old Ss actively ingested the diet, and their intake was related to the length of deprivation. Ss decreased their ingestive responding after they had consumed large volumes of milk. In addition, 1-, 3-, and 6-day-old Ss, when 24-hr deprived, exhibited an intense behavioral activation in response to milk infusion. The behavioral activation appeared to be stimulated primarily by taste and the opportunity to swallow. Milk infusions did not produce activation in older Ss; their behavior was more exclusively ingestive and food directed. Results demonstrate that (a) from birth, rat pups are capable of an active form of ingestion, independent of normal suckling from the mother; (b) such ingestion is controlled by physiological factors; (c) food has arousing properties in young animals; and (d) as pups grow older, their ingestive responding is refined from a generalized and nondirected activation to specific and directed feeding responses. (57 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of desalivation on drinking and air licking induced by water deprivation and hypertonic saline injections.

Previous studies show that desalivate (DS) rats drink more water than controls when maintained on a diet of dry food, but drink less than controls after a period of water deprivation. In the present series of studies, a total of 14 male and 2 female naive hooded rats served as Ss. Results show that DSs ate less food than sham operates (SHs), indicating that DSs' body fluids probably do not become as hyperosmotic as those of the SHs. When Ss were maintained on a moist mash during water deprivation, subsequent water intake and air licking were about the same for DSs and SHs. After combined food and water deprivation, both groups air-licked at greatly reduced rates. After subcutaneous injections of hypertonic saline, DSs air-licked just as much as SHs. It is concluded that DSs drink less after water deprivation because they eat less dry food than SHs during deprivation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Influence of sympathectomy on the lateral hypothalamic lesion syndrome.

Two experiments with male Long-Evans rats examined sympathetic involvement in the lateral hypothalamic (LH) lesion syndrome. Ss were surgically or chemically sympathectomized and then given LH lesions. At 24 hrs postlesion, lesion-induced hyperglycemia but not hyperthermia was attenuated by splanchnicectomy and celiac ganglionectomy. Hyperthermia but not hyperglycemia was attenuated by adrenal demedullation, adrenalectomy, and daily neonatal guanethidine (50 mg/kg) treatment. Guanethidine-sympathectomized Ss also displayed lower basal temperatures, more perilesion chromatolysis, and more severe external symptoms than controls. No form of sympathectomy affected lesion-induced gastric pathology, plasma gastrin concentrations, or body weight loss, nor did any sympathectomy influence the recovery of ingestive behavior, daily food intake, the feeding response to 2-deoxy-dextro-glucose, or body weight maintenance in recovered LH-lesioned Ss. Results suggest that sympathetic hyperactivity contributed to some aspects of the acute LH syndrome: Hyperglycemia resulted from sympathetic outflow to the abdomen, whereas hyperthermia was determined by circulating catecholamines and extra-abdominal sympathetic innervation. Findings fail to support the hypothesis that chronic increases in sympathetic tone are responsible for the reduced food intake and body weight of the LH-lesioned Ss. (47 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Failure by deprived hamsters to increase food intake: Some behavioral and physiological determinants.

Investigated the behavioral and physiological determinants of postfast anorexia in 165 golden hamsters. Six experiments varied the postfast feeding in photoperiods, feeding in different hamster strains, the effects of a liquid diet, Ss' adaptation to a restricted water schedule, food intake as a function of housing, and physiological changes during food deprivation. Postfast anorexia and/or the failure to adapt to a feeding schedule were not restricted to a particular photoperiod condition or hamster strain. The anorexia was also observed with a liquid diet, but Ss showed large increases in water intake on a water deprivation schedule. When Ss were group-housed, they pouched food during scheduled feeds and ate it later: Meal size was not increased. Measures of gastric fill and plasma metabolites indicated that filling and emptying of the forestomach occurred with a periodicity similar to that of spontaneous meals; data are consistent with strong peripheral satiation/satiety mechanisms in this species. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Inducing belief instability without a persuasive message: The roles of attitude centrality, individual cognitive differences, and sensory deprivation.

Examined the effects of sensory deprivation and attitude centrality on belief instability. 24 paid volunteers, recruited through a university newspaper, completed individual difference measures (including the Comprehensive Abilities Battery, the Role Construct Repertory Test, and the Paragraph Completion Test) and were assigned to either a control or an experimental group. Experimental Ss lay in a dark, silent chamber with water and liquid diet food available for 24 hrs while controls participated in their normal routines. All Ss then responded to instruments assesing belief instability. Results indicate greater belief instability among experimental Ss on peripheral and central attitudes. Less belief instability was found among both experimental and control Ss on the central attitude. Measures of intelligence and conceptual complexity were not significantly correlated with instability. Data indicate that the uncertainty model of attitude change is useful in explaining effects of sensory deprivation on persuasibility. (11/2 p ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Nonphysical contact between cagemates alleviates the social isolation syndrome in C57BL/6 male mice.

In rodents, social isolation during the early postweaning phase induces several behavioral abnormalities, commonly referred to as the isolation syndrome. We attempted to identify the contribution of the selective deprivation of physical contact to the emergence of the isolation syndrome. To this end, we devised a pseudoisolated housing condition in which male 3-week-old C57BL/6 mice were caged in pairs, but were separated by a transparent perforated partition allowing only nonphysical contact, and compared it with the classical isolation procedure and standard laboratory group housing. Locomotor activity, acoustic startle reactivity, and amphetamine-induced hyperactivity were enhanced by isolation, but neither anxiety nor prepulse inhibition of the acoustic startle response was affected. Pseudoisolated mice were comparable to grouped controls in their acoustic startle response and locomotor reactivity to amphetamine, but they were as active as isolated animals in the predrug sessions of the open field. Furthermore, pseudoisolation also exerted its own unique effects, namely, anxiolysis. Our results demonstrated for the first time the relevance of nonphysical contact including its ability to undermine the emergence of the isolation syndrome in mice. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of obesity in diabetic mice pair-fed with lean siblings.

Investigated the role of hyperphagia in the obesity of the diabetic mouse, C57BL/6J/db/db. Ingestion patterns and the amount of food for 25 diabetic mice were controlled by yoking their food intake to that of 16 nonobese siblings obtaining their food by barpressing. Over a period of 6 wks, young (initial ages were 28 days) pair-fed diabetic Ss accumulated 42% more body weight and approximately 5 times more extractable carcass lipid than did their siblings. Weight gain and absolute levels of carcass fat were reduced in food-restricted diabetic Ss compared with db Ss on unrestricted food intake. However, carcass fat as percentage of wet carcass weight was virtually identical in the restricted and unrestricted db rats (47.6 vs 49.6%). From these results it is concluded that the heightened adiposity of the diabetic mouse does not require hyperphagia for its expression and thus represents a metabolic obesity. (34 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Predatory attack by rats: Its relationship to feeding and type of prey.

Investigated mouse killing behavior in 5 experiments with male Long-Evans rats (N = 233). Hunger potentiated mouse killing by naive Ss, but not by Ss familiarized with mice before and during food deprivation. Once Ss had been made hungry, mouse killing was unaffected by increasing or decreasing severity of food deprivation or by time of testing with respect to a regular feeding hour. Ss fed either dead mice, powdered chow, or hard pellets while on cyclic food deprivation were about equally likely to kill, showing that hunger does not indirectly potentiate killing by increasing practice of responses like pouncing and biting. Whether hungry or not, killers were likely to eat their prey, whereas nonkillers were unlikely to eat the same prey. Ss killed 12-14 day-old rat pups as often as they killed mice, but killed weanling rat pups less often. Findings question several common notions regarding predatory aggression. (26 ref.) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Cholecystokinin elicits the complete behavioral sequence of satiety in rats.

Observed and scored the behavior of intact rats and rats with chronic gastric fistulas during a 60-min test period when they were offered liquid diet after 17 hr of food deprivation. The same 5 adult male Sprague-Dawley rats were employed in 2 experiments. Intact Ss and Ss with closed fistulas displayed a specific behavioral sequence at the end of each meal: They stopped eating, engaged in grooming and exploration for a short time, and then rested or slept. Thus, a fixed behavioral sequence characterized satiety in Ss. Although the behavioral sequence of satiety was fixed, the cessation of feeding was not a sufficient condition for the appearance of the rest of the sequence: Quinine adulteration of the liquid diet stopped sham feeding but did not elicit the complete sequence. Intraperitoneal injection of the intestinal hormone cholecystokinin during sham feeding, however, elicited the complete sequence of satiety. The observation that cholecystokinin not only stopped feeding but elicited the complete sequence of satiety supports the hypothesis that endogenous cholecystokinin is a satiety signal for the rat. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

External validity of laboratory fear assessment: Implications from two case studies.

Exposed 1 snake-phobic woman and 1 spider-phobic woman to a live snake or spider after they received systematic desensitization. In one assessment condition the 2 Ss were asked to approach and handle a caged snake or spider as in the traditional behavioral approach test, whereas in the other condition the Ss were exposed to the uncaged phobic stimuli. Both Ss manifested substantially greater physiological and cognitive distress while looking at the uncaged stimuli from a distance of 30 ft than when actually touching the caged snake or spider. Although both Ss were able to touch the caged snake or spider, they still reported being unable to engage in behaviors that were previously inhibited because of their phobia. Both Ss emphasized the importance of feeling in control when the phobic stimulus was caged but feeling out of control when the phobic stimulus was uncaged. Implications for the external validity of the behavioral approach test are discussed. (20 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effectiveness of estradiol in preventing and reversing obesity induced by ovariectomy and high-caloric diet in female rats.

Four experiments with 77 female Holtzman rats examined the effects of estradiol benzoate (EB) on food intake, body weight (BW), ano-nasal length, and BW/body length ratio in ovariectomized (OVX) and intact Ss maintained on control or high-fat diets and of OVX and intact Ss that had been reduced by deprivation. EB was highly effective in preventing the increase in food intake, BW, and ano-nasal growth after OVX; it was relatively ineffective in reversing BW gain after OVX. However, when ano-nasal length was also considered, BW was effective in returning OVX Ss to an appropriate BW for their increased ano-nasal length. Intact Ss fed a high-caloric diet did not exhibit an increased rate of ano-nasal growth, which indicates that the skeletal growth that occurred after OVX was not simply a result of increased food intake. It is concluded that EB modulates food intake and BW by multiple mechanisms, one of which is by modulating skeletal growth. The nature of the effect of EB on BW of intact Ss suggests that this effect occurs by still another mechanism. (13 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

The ontogeny of feeding in rats: III. Thermal determinants of early ingestive responding.

High ambient temperatures (38°C) stimulated high spontaneous levels of activity and high frequencies of behaviors normally associated with ingestion (mouthing and probing), particularly in young, 3- and 6-day-old Charles River CD rat pups (Exp I). The level of spontaneous behavior was highly correlated with body temperature and also depended on deprivation condition. Temperature played an important role in determining responses to food stimuli as well. When Ss were fed by oral infusion (Exp II) or by placing milk on the floor beneath them (Exp III), warm ambient temperatures were required for active ingestion. In Exp IV, body temperature and ambient temperature were manipulated independently to assess their relative importance for Ss' feeding behavior. Ss with a low (29°C) or normal (34°C) core temperature at the start of testing were fed in either a 24°C or a 34°C ambience. Regardless of body temperature, Ss' levels of intake, activity, mouthing, and probing were higher in a warm than in a cool ambience. Therefore, the suppressed ingestive behavior of Ss fed at cool temperatures occurred not simply because Ss became hypothermic and inactive. Perceived warmth appears to be a significant contextual cue that regulates pups' responses to food stimuli. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Predation, aggression, and activation levels in food-deprived sunfish (Lepomis macrochirus and L. gibbosus): Motivational interactions.

Three experiments investigated the effects of food deprivation on several behavioral categories in a total of 56 bluegill and pumpkinseed sunfish ( Lepomis macrochirus and L. gibbosus, respectively). In Exp I, predatory behavior and general activity were observed under 5 levels of deprivation. For both species, predation measures increased in a similar negatively accelerating manner with increasing deprivation, while activity changed in a more complex fashion. Exp II examined the effects of deprivation on activity in a novel environment and showed that the deprivation effects of Exp I were masked by the response to the new setting. In Exp III, measures of aggression toward intruders of each species were recorded from resident fish of both species under 3 levels of food deprivation. Both species were more aggressive toward conspecifics, and bluegills were more aggressive overall. Aggression was significantly affected by food deprivation, with the effects dependent on the species making up the pair. Theories of motivational summation, generalized drive, and activity-mediated aggression are seen as inadequate to explain the differential effects of hunger on the 3 behavioral categories observed. A dynamic boundary-state model of behavior was, however, found to predict the motivational interactions observed between distinct behavioral control systems. (46 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Estrus- and ovariectomy-induced body weight changes: Evidence for two estrogenic mechanisms.

Estrogenic modulation of body weight in female rats is usually thought to result indirectly from estrogenic modulation of food intake. However, present data from 5 experiments with 79 female albino rats suggest that estrogens influence body weight by at least 2 mechanisms, 1 of which is independent of changes in food intake. When Ss were ovariectomized (Ovx) and food intake was limited to preoperative levels, Ovx Ss nonetheless gained large amounts of body weight. Although Ovx Ss gained more weight than controls on the same amount of food, during 33 hrs of food deprivation Ovx and control Ss lost weight at the same rate, indicating that the prefasting metabolic rates of the 2 groups were similar. During the 1st 40 days after surgery, the ano-nasal lengths of Ovx Ss increased twice as fast as that of intact Ss, which suggests a mechanism for the gradual increase in weight induced by Ovx. The weights of intact Ss followed a regular 4-day cycle during ad lib feeding, but when the estrus-associated decrease in food intake was prevented, the cyclic weight changes were altered. Thus estrogens appear to regulate body weight by modulation of food intake and modulation of ano-nasal growth or other metabolic processes. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)