Independent effects of estradiol on water and food intake.

Conducted 6 experiments to examine the effects of estradiol on ingestive behaviors of guinea pigs. Estradiol treatment was found to reduce water intake independently of its actions on food intake and body weight. In the 1st experiment, minimum intake and body weight of 17 intact female guinea pigs coincided with rupture of the vaginal membrane, the estimated time of ovulation. In Exp II, injections of 3 μg of estradiol benzoate (EB)/day to 7 ovariectomized females significantly depressed food intake, water intake, and body weight, compared with 7 Ss that received oil injections. Reducing food rations to 30% below ad lib levels in Exp III by itself had no significant effect on drinking in ovariectomized Ss. In Exp IV, therefore, ovariectomized females were first placed on a food ration 30% below ad lib levels and then injected daily with either 3 μg of EB or oil. Compared with oil injections, these EB injections significantly reduced water intake, while food intake did not decline significantly. Findings indicate that estradiol operates through different mechanisms to affect water intake and food intake. (40 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of 4-hydroxyamphetamine on in vivo brown adipose tissue thermogenesis and feeding behavior in the rat.

Examined the influence of 4-hydroxyamphetamine (4-OHAM) on food and water intake and in vivo brown adipose thermogenesis in 2 experiments with 22 female Long-Evans rats. In Exp I, Ss were treated with 4-OHAM (0.25, 0.50, 1, or 2 mg/kg, ip) prior to assessment of interscapular brown adipose tissue (IBAT) thermogenesis. The 4-OHAM treatment induced dose-dependent activation of IBAT thermogenesis consistent with the enhanced serum levels of norepinephrine and epinephrine observed in 4-OHAM-treated Ss immediately after temperature measurement. In Exp II, the influence of 4-OHAM on food and water intake was assessed during 120-min test intervals in Ss fed food and water ad lib. Although there was a trend for 4-OHAM to increase water intake, there was no significant effect of 4-OHAM (0.40, 0.80, 1, 2, and 4 mg/kg) on either food or water intake. Data suggest that IBAT thermogenesis does not play a role in the anorexia induced by amphetamine or in the regulation of feeding. (19 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

An evaluation of dipsogenic stimuli in the African Green monkey.

In Exp I, elevations in the concentration of plasma angiotensin II (AII) and decline in plasma aldosterone (Ald) were noted in 6 female African Green monkeys at 48 hrs of water deprivation but not subsequent to an equivalent duration of food deprivation, compared with nondeprived levels. In Exp II, drinking was initiated following treatment with AII, hypertonic saline, and the beta-adrenergic stimulator isoproterenol. Concomitant elevations in plasma AII concentrations were measured following isoproterenol injection, but not after AII or hypertonic saline injection, when compared with isotonic saline treatment. Elevations in plasma Ald levels were noted following AII injection. Exp III evaluated dipsogenic additivity of stimuli by comparing the volumes of water consumed following isoproterenol or hypertonic saline injection with the intake resulting from combined treatment with isoproterenol and hypertonic saline. Additivity was tested under ad lib conditions and following adaptation to a daily water deprivation regimen. Results of the first 2 experiments generally agree with predictions based on the respective contributions by intracellular dehydration and extracellular fluid volume depletion to thirst. However, additivity of thirst stimuli was not demonstrated in Exp III. (50 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Intraventricular insulin and the level of maintained body weight in rats.

To determine whether central insulin administration lowers the level around which body weight is regulated, insulin (6 mU/day) or saline was infused into the 3rd ventricles of 4 groups of rats. One insulin-infused and 1 saline-infused group were food-deprived for 3 days and were then returned to an ad lib feeding schedule. The other 2 groups were maintained on ad lib feeding throughout. Insulin-infused food-deprived rats lost weight at a significantly greater rate than saline-infused food-deprived rats. In ad lib fed rats, insulin infusion caused a significant reduction of food intake and weight relative to saline-infused controls. When formerly food-deprived rats were returned to ad lib feeding, they gained weight, and this was significantly more pronounced in the saline-infused than the insulin-infused group. The body weights of the two insulin-infused groups converged on a value approximately 9% below the average of the 2 saline infused groups. Findings suggest that the 3rd-ventricular infusion of insulin does not incapacitate the rats and that they can alter their food intake either upward or downward to attain a new weight. Results also support the hypothesis that direct administration of insulin into the brain determines the level of weight maintained by the animal. (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thirst and sodium appetite after colloid treatment in rats with septal lesions.

Previous experiments in which angiotensin II (AII) and mineralocorticoids were administered to rats have suggested that these hormones play a natural role in mediating thirst and sodium appetite. This hypothesis was examined by making use of 20 male Sprague-Dawley rats with septal lesions, which have an apparent sensitivity to the central effects of AII, and by studying their behavioral response to sc treatment with 5 ml of a 30% polyethylene glycol solution, which produces hypovolemia and thereby stimulates the secretions of renin and aldosterone. The induced thirst and sodium appetite both were markedly enhanced in the brain-damaged Ss. However, water intake was not increased when the hypovolemia was moderate, and sodium appetite was augmented only when Ss had been sodium deprived, a procedure known to potentiate aldosterone secretion. Findings support suggestions that while AII normally contributes little to thirst, it may help to mediate sodium appetite in rats when aldosterone is abundant. The 2 drives were not elicited uniformly; those Ss that drank the most water after colloid treatment consumed the least saline. While septal lesions may sensitize the rat's brain to the sodium-appetite-eliciting effects of AII as well as to its dipsogenic effects, sodium appetite may emerge only if the induced thirst is not too pronounced. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thyroxine treatment reduces the anorectic effect of estradiol in rats.

Examined a possible interaction between thyroxine and estradiol in the control of feeding in female Sprague-Dawley rats. 14 ovariectomized Ss were given daily injections of 9.8 μg/100 g of body weight of 1-thyroxine (TX). Another 14 Ss received 0.15 ml of saline (SAL) subcutaneously each day, and food intake was measured for both groups daily. After 15 days of treatment, 8 Ss from each group were also given a single injection of 6 μg of estradiol benzoate (EB), and the remaining 6 Ss of each group received peanut oil vehicle. It was found that TX-treated Ss showed a significantly smaller drop in food intake after EB than did SAL-treated Ss. This TX-induced decrease in responsiveness to EB may be related to effects of TX on general metabolism. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Opiates and medial hypothalamic knife cuts cause hyperphagia through different mechanisms.

In Exp I, male Sprague-Dawley rats were given bilateral parasagittal medial hypothalamic knife cuts (KCs) or a sham procedure and fed a high-fat diet. KC and sham-operated Ss were approximately equally sensitive to the suppressive effects of naloxone (0.1–20 mg/kg, subcutaneously [sc]) on food intake. Ketocyclazocine (0.1–20 mg/kg, sc) generally increased daytime food intake in sham-operated Ss; in contrast, the normal hyperphagia of KC Ss was in most cases either unchanged or decreased by ketocyclazocine. In Exp II, neither diet composition nor hypothalamic KCs significantly affected the feeding responses to naloxone or the stimulatory effects of butorphanol tartrate (0.1–20 mg/kg, sc). It was hypothesized that the differential effects of ketocyclazocine in KC and sham-operated Ss were a consequence of the sedative effects of the drug combined with the elevated baseline of the KC Ss. This hypothesis was supported by Exp III, which showed that ketocyclazocine also reduced nocturnal intake in unoperated Ss and that butorphanol increased intake. That feeding responses to naloxone and butorphanol were essentially unchanged by hypothalamic KCs suggests that the opioid feeding system is independent of the longitudinal feeding inhibitory pathway believed to be involved in KC-induced hyperphagia. (36 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Tolerance to amphetamine anorexia: Role of learning versus body weight settling point.

Conducted 3 experiments with male Sprague-Dawley rats to study the development of tolerance to amphetamine (AM) anorexia. In Exp I, 19 Ss that had become tolerant to the suppressant effect of AM on milk intake were anorexic when offered other foods or water. These results appear to support a conditioning interpretation. In Exps II (38 Ss) and III (24 Ss), Ss made tolerant with milk as the diet showed prolonged anorexia when switched to Purina pellets or slightly bitter milk; but when switched from pellets or adulterated milk to milk, tolerant Ss were anorexic only 1 day and then ingested significantly more of the new diet. Results are inconsistent with a conditioning interpretation. Tolerant Ss maintained their weight below the level of saline controls despite the recovery of food intake, and the level at which they maintained their weight varied with the palatability of the diet. These results suggest that AM lowers the settling point for body weight and that tolerance to this effect does not develop. Thus, the reinstatement of prolonged anorexia when apparently tolerant Ss were switched to a less palatable diet can be understood as an attempt to attain a lower weight level. (32 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Effects of aldosterone and deoxycorticosterone on food intake and body weight.

Conducted an experiment with 48 female adrenalectomized Sprague-Dawley rats, who were injected daily with aldosterone (.25 mg/kg) or deoxycorticosterone (3 mg/kg) in combination with corticosterone. The mineralocorticoids increased food intake and weight gain well beyond that of controls receiving only corticosterone injections. The weight gain was not wholly dependent on increased food intake, as separate groups of Ss maintained on a restricted diet (10 g of laboratory chow/day) also displayed significant mineralocorticoid-stimulated weight gain. Although carcass composition was not directly determined, the undifferentiated wet/dry tissue ratios, hematocrit values, and nasoanal lengths found across groups suggested that the observed effect of mineralocorticoids was on body fat. Aldosterone and deoxycorticosterone can have important actions on energy metabolism as well as on sodium regulation. (9 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Stress and ulceration in the glandular and nonglandular portions of the rat's stomach.

Previous studies indicate that conditioned fear and conflict produce ulceration in the nonglandular portion of the rat's stomach (rumen), while immobilization produces ulceration in the glandular portion (corpus). The present 3 experiments were conducted with Maudsley Reactive, Maudsley Nonreactive, and male Sprague-Dawley rats (N = 66). Exp I and II tested the course of ulceration in the corpus and rumen under stress conditions. Ulceration was induced in the corpus by partial restraint. Ulcerated Ss were then exposed to conditioned fear for 72 hrs (Exp I) and 48 hrs (Exp II) and were compared with controls. Exp I showed that glandular lesions healed while nonglandular lesions developed in food-deprived Ss. Nonglandular ulcers did not appear during the 48 hrs of Exp II. Exp III showed a positive relationship between rumenal ulceration and food deprivation. Rumenal ulceration induced by conflict and conditioned fear procedures mainly seems to reflect the suppression of food intake by these procedures. (22 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Reactivity of normal and VMH-lesion rats to quinine-adulterated foods: Negative evidence for negative finickiness.

Conducted 2 experiments with ventromedial hypothalamic (VMH) and normal rats to examine (1) whether the anorexic properties of quinine depend on quinine's sensory properties or on its postingestive effects, and (2) whether VMH rats overrespond to quinine adulteration. These issues were examined by comparing the feeding adjustments to quinine by VMH and normal male Long-Evans rats in a sham-feeding situation and under normal feeding circumstances, on Ss' initial exposure to this drug. In Exp I, 17 Ss received VMH lesions or sham lesions before being sham fed with various concentrations of quinine. In Exp II, 18 lesioned or sham-lesioned Ss were fed unadulterated food for 12 days, followed by a meal adulterated with quinine, 2 days of pure mash, and 1 day of quinine. Quinine caused significant depression of food intake in Ss. Little evidence exists for a conclusion that VMH rats are more reactive than normals to quinine-adulterated foods. Results suggest that major food intake perturbations of VMH rats are in response to hedonically positive dietary manipulations. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Rats (Rattus norvegicus) do not prefer salted solid food.

Conducted 3 studies to evaluate the ingestive responses of Sprague-Dawley rats to salt in foods and to determine whether prior exposure to salted foods influenced their intake. In Exp I, 16 Ss were given 1-hr access to salted and unsalted foods (e.g., potato chips, peanuts, soup) commonly consumed by humans in the salted form. In each choice situation, rats consumed more of the unsalted variety of solid food. In Exp II, the concentration of salt in a wider variety of foods was varied. 15 Ss were allowed a choice of a given salt concentration or the unsalted food. In no case was the salted solid food eaten in excess of the unsalted solid food, and in general, more of the unsalted solid food was eaten. In Exp III, 2 groups of 8 Ss were given exposure from weaning to either salted or unsalted potato chips for 3 mo. Exposure did not alter the Ss' relative intake of salted chips. When given a choice, more unsalted chips were consumed by both groups. Results indicate that sodium-replete Sprague-Dawley rats generally prefer unsalted solid foods to salted ones. (31 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Oral somatosensory factors in dietary self-selection after food deprivation and supplementation.

In 2 experiments with 72 male albino Sprague-Dawley rats, trigeminally deafferented Ss were subjected to nutritional stresses while being allowed to balance protein and carbohydrate intake from 3 separate dietary fractions. Partially trigeminally deafferented Ss that had recovered a normal protein ratio (protein/total intake) underwent total food deprivation (Exp I) or intragastric (IG) supplementation of protein or carbohydrate suspensions (Exp II). In response to deprivation, control Ss increased protein intake above ad-lib levels, but not carbohydrate intake. In response to IG supplementation, they decreased protein intake disproportionately more than carbohydrate intake when the fluid consisted of protein and vice versa when the fluid consisted of carbohydrate. The recovered deafferented Ss showed no selective increase in protein intake after deprivation and no differential compensation to nutrient supplementation. This suggested that recovery of the protein ratio after partial trigeminal deafferentation could not fully replace the function of trigeminal somatosensory input. The possible roles of other orosensory and of postingestional factors for recovery are discussed. (16 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Daily variations of platelet aggregation in relation to blood and plasma serotonin in diabetes

INTRODUCTION: An increase in digitalis-like substances has been reported in deoxycorticosterone acetate (DOCA)-salt hypertensive rats. We hypothesized that the role of saline and unilateral nephrectomy in DOCA hypertension may be due to stimulation of endogenous digitalis-like substances. METHODS: We investigated the effects of digoxin and DOCA alone and in combination in intact rats drinking water. Forty male Sprague-Dawley rats were used (body weight 223-298 g). RESULTS: Neither digoxin (40 micrograms/kg per day, by gavage, for 35 days, n = 10) nor DOCA (30 mg/kg twice a week, subcutaneously, for 5 weeks, n = 10) caused a consistent increase in blood pressure in intact rats drinking water. In contrast, combined digoxin and DOCA administration (n = 10) increased systolic blood pressure from day 18 of treatment onwards, to a maximum at day 34 compared with sham-treated rats (n = 10). There were no consistent changes in water intake, urine volume, urinary sodium or potassium excretion, or plasma sodium or potassium concentration with digoxin treatment. DOCA increased water intake and urine volume, and caused an initial decrease in urinary sodium excretion, but no change in urinary potassium excretion or plasma sodium concentration. Plasma potassium excretion was lower in DOCA- than sham-treated rats. CONCLUSION: Combined digoxin and DOCA administration in intact rats drinking water increased blood pressure significantly compared with either drug alone, raising the possibility that the mechanism by which nephrectomy and salt loading contribute to DOCA hypertension in the rat might be through stimulation of endogenous digitalis-like substances.     

Use of synthetic oligonucleotides for inhibition of factor NF-kappa B

The effect of the proportion of clover in the diet (200, 500 or 800 g/kg total dry matter (DM) on milk production of cows housed indoors and fed on a mixture of perennial rye-grass and white clover was measured in mid (Expt I) and late (Expt II) lactation. Higher clover contents increased the nutritive value of the diets, resulting in increased energy and protein intakes. DM intakes of cows offered 500 or 800 g clover/kg DM diets ad lib. (Expt I and Expt II, Period 1) were not significantly different but were 11-17% greater (P < 0.05) than intakes of cows fed on 200 g clover/kg total DM diets. Cows offered restricted allowances (Expt II, Period 2) had similar intakes irrespective of diet. In Expt I cows fed on 500 or 800 g clover/kg DM diets ad lib. produced 30 or 33% respectively more milk (P < 0.05) than cows fed on 200 g clover/kg total DM diets. During Expt II, Period 1, cows fed on 500 or 800 g clover/kg DM diets ad lib. produced 18 or 16% more milk (P < 0.05) respectively than cows given 200 g clover/kg total DM diets. In both these experiments the increased milk yields were due to increased intake and the higher nutritive value of the high clover diets. There was no difference in the feed conversion efficiencies of cows if maintenance energy requirements were taken into account. However, cows on restricted allowances (Expt II, Period 2) showed no significant difference in milk yield, indicating that the effect of increased nutritive value was very slight. There were no consistent effects on milk fat, protein or lactose concentrations. Concentrations of blood and milk urea increased as the clover content of the diet increased (Expt 1 only), and this was associated with increased milk non-protein N and a decreased ratio of casein N: total N. Both trials indicated an optimum clover content in the diet for milk production of 600-700 g/kg total DM.     

Bradykinin suppresses alcohol intake and plays a role in the suppression produced by an ACE inhibitor

The possible role of the endogenous kinins in the control of alcohol intake was assessed in two experiments. In Experiment 1, naive rats, maintained on ad lib food and water, were given daily 40-min access to a 6% (w/v) alcohol solution and water. Daily intraperitoneal (IP) injections of captopril (20 mg/kg) significantly reduced alcohol intake, while pretreatment with subcutaneous (SC) injections of the bradykinin antagonist [D-Phe7]-bradykinin (100-300 micrograms/kg) attenuated the suppressive effect of captopril on alcohol intake. The saline vehicle or the bradykinin antagonist alone did not alter alcohol intake. In Experiment 2, bradykinin was administered daily at 100, 200, and 400 micrograms/kg doses SC either alone or in combination with captopril 10 mg/kg IP. Neither bradykinin nor captopril by themselves changed alcohol or water intake. Bradykinin combined with captopril stimulated water intake and reduced alcohol intake by up to 70%. This effect was not due to drug-induced changes in the pharmacokinetics of alcohol. The angiotensin II receptor antagonist [Sar1,Thr8]-angiotensin II at 250 and 500 micrograms/kg SC attenuated the stimulation of water intake but not the reduction in alcohol intake. It is suggested that by inhibiting kininase II, ACE inhibitors extend the duration of action of bradykinin and thereby unmask a potent inhibition of alcohol intake mediated by kinins--an effect that is dissociable from the accompanying stimulation of water intake. Taken together, these results point to an involvement of the kinin system in the regulation of alcohol intake and in particular to a role of bradykinin in the suppressive effect of ACE inhibitors on alcohol intake.     

Antidipsogenic role of the E-prostaglandins.

Prostaglandin E? (PGE?) is antidipsogenic when administered into the lateral cerebral ventricle of the rat. In 8 experiments with a total of 211 male Sprague-Dawley rats, PGE?, at a dose of 1 μg, suppressed water intake induced by centrally administered angiotensin II (AII) or carbachol, sc administered polyethylene glycol, and water deprivation. Even at this high dose, PGE? did not reduce water intake due to cellular dehydration. As the dose of PGE? was reduced, its suppressant effects became more specific to AII-induced drinking, with a dose of 10 ng yielding a significant suppression only in the case of AII-induced drinking. Even at a high dose (1 μg), the PGE? suppression of ingestion was specific to water intake. Although PGE?-treated Ss reduced food intake if they were not hydrated prior to access to food, no reduction in food intake was seen when they received water by gavage before food presentation. Since PGE?-like substances are synthesized in the brain, these data suggest the possibility that the prostaglandin may be involved in the regulation of water balance as a component of a reciprocal system in which water intake initiated by the activation of the renin-angiotensin system is halted by the synthesis and release of PGE. (29 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Differential effects of contextual change on latent inhibition and on the habituation of an orienting response.

In Exp I, using 20 female hooded Lister rats, the habituation of the orienting response (OR) shown by Ss to a discrete visual stimulus (a 10-sec light) in a given training context (A) was monitored. Dishabituation occurred, in that the OR returned to its initial level, when the light was presented in a different and novel context (B). In Exp II, 24 female rats received 2 sessions/day, one in each of the 2 contexts. For experimental Ss, the light was presented in Context A until the OR habituated. In the test phase, the light was presented in Context B, but the OR was not restored, suggesting that the dishabituation seen in Exp I depended on the absolute novelty of Context B. In Exp III, Ss from Exp II were required to form a light–food association in both contexts. Slow learning was observed in Ss trained with the familiar light in Context A, but learning proceeded normally with the familiar light in Context B. Thus, a context change that failed to produce dishabituation was enough to prevent the occurrence of a latent inhibition effect. (35 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Thirst and sodium appetite after colloid treatment in rats.

In 3 experiments with male albino Sprague-Dawley rats, injection of polyethylene glycol (PEG) solution (10–30% solution) produced a progressive sequestration of extracellular fluid at the injection site. PEG-treated Ss showed both thirst and sodium appetite. However, water intake began 1–2 hrs after the injections, whereas consumption of NaCl solution did not start until 3–4 hrs later. Then Ss ingested both fluids alternately until plasma volumes were restored, whereupon saline intake became even more prominent and water was consumed due to induced osmoregulatory needs. These 3 phases were seen regardless of the dose of PEG or the concentration of saline. After maintenance on a sodium-deficient diet for 2–4 days or after bilateral adrenalectomy, Ss increased their intake of saline immediately after PEG treatment. Findings suggest that the delayed onset of sodium appetite after PEG treatment that occurred when Ss were maintained on standard sodium-rich chow resulted from the buffer provided by surplus extracellular fluid in those Ss. They further suggest that sodium appetite may be stimulated by a decreased availability of sodium in the brain. (44 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Interaction of hydration and subfornical organ lesions in sodium-depletion induced salt appetite.

The authors tested whether the level of hydration after furosemide diuresis and 22 hrs of sodium depletion affects the amount of water or 0.3 M NaCl solution consumed by rats with intact brains or with lesions of the subfornical organ (SFO). Rats received 2 (underhydrated) or 10 (euhydrated) ml/kg water by gavage as the only fluid input 2, 4, and 20 hrs after 10 mg/kg furosemide. These hydration treatments had little or no effect on the amount of saline consumed in 2 hrs by intact rats. SFO lesions reduced water intake regardless of hydration condition. Euhydrated, SFO-lesioned rats drank a normal amount of saline, but underhydrated, lesioned rats drank less saline than any other group. Thus, euhydration may facilitate salt appetite in SFO-lesioned rats, and the deficits in salt appetite noted in SFO-lesioned rats may result from deficits in water ingestion rather than from a destruction of angiotensin II receptor sites that directly provoke salt appetite. (PsycINFO Database Record (c) 2010 APA, all rights reserved)