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PubMed1997

Brain oxytocin receptor antagonism disinhibits sodium appetite in preweanling rats.

Previous studies have shown that preweanling rats do not express an endogenous sodium appetite until postnatal day 12. The present studies tested the hypothesis that prior to 12 days of age sodium appetite, induced by either central administration of angiotensin II (AngII) or adrenalectomy, is inhibited by endogenous oxytocin (OT). After 9- or 10-day old animals were given a central injection of either an OT receptor antagonist or vehicle, they were infused intraorally with 4% sodium chloride which the animals could either swallow or reject. Intake was measured as the increase from initial body weight. There was very little sodium consumption by vehicle-injected animals that received sham surgery or adrenalectomy; however, the OT receptor antagonist significantly elevated sodium consumption in adrenalectomized animals. The OT antagonist also potentiated sodium intake after AngII pretreatment. These results suggest that the neurochemical circuits necessary for the expression of sodium appetite are present and functional as early as postnatal day 9; however, until 12 days of age this behavior is suppressed by endogenous OT.

Adrenalectomy↗
PubMed1988

Polycose and sucrose appetite in rats: influence of food deprivation and insulin treatment.

Rats appear to have two different carbohydrate tastes, a sweet taste for sugars, and a "polysaccharide" taste for starch and starch-derived polysaccharides. The present study explored the possible functional significance of this dual taste system by comparing the effects of food deprivation and insulin treatment on the appetite for sucrose and Polycose. Food deprivation (24 h) produced comparable increases in the 5-min and 30-min intakes of Polycose and sucrose (1-8%) solutions in adult female rats. Polycose and sucrose intakes were also increased to a similar degree by insulin injections (1 unit/kg) during brief (3-min) one-bottle tests. In brief two-bottle tests, however, insulin treatment tended to shift the rat's preference from sucrose to Polycose. Chronic treatment with insulin increased the long-term intake of 30% Polycose and sucrose solutions, with the effect being more pronounced with Polycose. These findings demonstrate that energy deficit states enhance the appetite for Polycose as much as or more than the appetite for sucrose.

Animals↗
PubMed1995

Influence of adrenal steroid hormones on sodium appetite of Balb/c mice.

The effects of adrenal steroid hormones on sodium appetite were determined in female Balb/c mice by the subcutaneous implantation for 7 days of slow-release pellets containing aldosterone, corticosterone, deoxycorticosterone (DOC) or 11-deoxycortisol, separately or in a "cocktail" combination. Placebo pellets were also implanted. The daily intake of 0.3 M NaCl was increased for 2 days by aldosterone (calculated 2.9 micrograms/day released) or corticosterone (240 micrograms/day) and for 7 days by DOC (4.8 micrograms/day). The combination of these steroids plus 11-deoxycortisol (95 micrograms/day) increased daily sodium intake nine-fold (days 3-7) and also increased water intake 1.5-fold. Placebo pellets had small effects on water intake on three days. Subcutaneous infusion of ACTH (Synacthen) at 2.8 micrograms/day for 7 days by mini-osmotic pump increased sodium intake five-fold and water intake three- or four-fold. Thus, several adrenal steroids evoked sodium appetite in Balb/c mice, DOC being the most potent at the doses used. The effects of individual steroids are consistent with their contribution to the effect of ACTH on sodium appetite.

Adrenal Cortex Hormones↗
PubMed1999

The effects of enteral tube feeding and parenteral nutrition on appetite sensations and food intake in health and disease.

Enteral tube feeding (ETF) and parenteral nutrition (PN) are unphysiological methods of feeding. They may not elicit the cephalic phase response because part or all of the gastrointestinal tract is bypassed, nutrients are typically given in liquid form by a continuous infusion over many hours and often overnight while patients sleep. Work conducted in animals, healthy subjects and patients suggests that nutrients delivered as ETF or PN are less effective in relieving appetite sensations than food intake. Distressing appetite sensations may even occur despite the provision by artificial nutrition of sufficient nutrients to meet requirements. The energy provided by ETF and PN is largely additional to oral food intake in humans eating ad libitum, although the extent to which this occurs may decrease with time. There is a need to establish ways (e.g. nutritional, pharmacological, psychological) to suppress appetite sensations and food intake when eating is contraindicated, and to enhance them when weaning from artificial nutrition is desirable.

Animals↗
PubMed2003

Acquisition of a palatable-food-sustained appetitive behavior in satiated rats is dependent on the dopaminergic response to this food in limbic areas.

Rats exposed to repeated unavoidable stress show decreased dopamine output in the nucleus accumbens shell (NAcS) and do not acquire vanilla sugar (VS)-sustained appetitive behavior (VAB). Rats treated with lithium for 3 weeks also show decreased NAcS dopamine output, yet they acquire VAB. Feeding a novel palatable food increases extraneuronal dopamine levels in the NAcS and medial prefrontal cortex (mPFC) in rats. In order to investigate the role of food-induced dopamine release in VAB acquisition, we studied by microdialysis the dopaminergic response in the NAcS and mPFC to the presentation and consumption of VS in satiated control rats, and in satiated rats exposed to repeated stress or lithium treatment. The dopaminergic response to VS was also studied in rats familiar with VS, or that had acquired VAB. In control rats, VS feeding was accompanied by increased dopamine output in the NAcS and mPFC, and one-trial habituation to this effect developed in the NAcS. Rats exposed to a 7-day stress showed reduced interest in VS pellets, and when fed VS they did not show a dopaminergic response in the NAcS and mPFC. Lithium-treated rats rapidly ate VS pellets and showed increased dopamine output in the NAcS and mPFC, with no habituation in the NAcS response. Rats familiar with VS and rats that had already learned VAB ate VS pellets. The first group showed a lower dopaminergic response to VS consumption than the control group, but the latter showed no dopaminergic response in the NAcS and mPFC. We propose that the limbic dopaminergic response to a novel palatable food plays a role in associative learning and that it is predictive of the competence to learn an appetitive behavior. Moreover, in our experimental conditions a phasic increase in mesolimbic dopamine no longer signals the VS stimulus once it has become a reinforcer in an appetitive task.

Animals↗
PubMed2002

Regulation of appetite in frail persons.

Aging is often accompanied by anorexia of aging, described as a decline in appetite resulting in a lower dietary intake, followed by unexplained weight loss and adverse effects on health. This article discusses the main causes of a lack of appetite in frail elderly people. It is clear that appreciation of hedonic qualities of foods declines with age, as does the ability to regulate food intake. Carefully controlled studies, however, have shown favorable results with interventions that stimulate appetite in, frail elderly people.

Aged↗
PubMedDate not supplied

Changes of hypothalamic and plasma vasopressin in rats with deoxycorticosterone-acetate induced salt appetite.

Mineralocorticoids play a predominant role in development of salt appetite and hypertension. Since vasoactive peptides could mediate the central effects of mineralocorticoids, we evaluated changes of immunoreactive (IR) arginine vasopressin (AVP) in the paraventricular (PVN) and supraoptic (SON) hypothalamic nucleus during DOCA-induced salt appetite. In one model, rats having free access to water and 3% NaCl during 9 (prehypertensive stage) or 21 days (hypertensive stage) received DOCA (s.c., 10 mg/rat/in alternate days). A decrease in the IR cell area, number of IR cells and staining intensity was obtained in magnocellular PVN of rats treated during 9 days. After 21 days IR cell area and number of cells in the PVN also decreased, but staining intensity of remaining cells was normal. The same parameters were unchanged in the SON. In another model, animals treated with DOCA during 9 days had only access to 3% NaCl or water. The IR cell area in PVN and SON significantly increased in mineralocorticoid-treated and control animals, both drinking 3% NaCl. Staining intensity (PVN and SON) and number of IR cells (PVN) also augmented in DOCA-treated animals drinking salt respect of a group drinking water. Plasma AVP in rats treated with DOCA and offered salt and water, exhibited a 2-2.5 fold increase at the time of salt appetite induction. Plasma AVP was substantially higher in rats drinking salt only, while the highest levels were present in salt-drinking DOCA-treated rats. Thus, peptide depletion in the PVN may be due to increased release, because reduced levels of hypothalamic and posterior pituitary AVP were measured in this model. In rats drinking salt only the substantial increase of IR AVP in the PVN and SON, may be due to dehydration and hyperosmosis. Because DOCA-salt treated rats showed higher AVP levels in the PVN compared to untreated rats drinking salt only, it is possible that DOCA sensitized PVN cells to increase AVP production. The results suggest the vasopressinergic system could mediate some central functions of mineralocorticoids.

Animals↗
PubMedDate not supplied

Appetitive responses to computer-generated visual stimuli by the praying mantis Sphodromantis lineola (Burr.).

Tethered adult female praying mantises, Sphodromantis lineola (Burr.), were presented with various computer-generated visual stimuli that moved against patterned or homogeneous white backgrounds in predetermined patterns and at predetermined speeds. The degrees to which the stimulus configurations elicited appetitive behaviors (attempting to approach and/or striking) indicated the relative degrees to which the stimuli were classified as prey. Mantises readily struck at cartoon "crickets" that subtended visual angles as great as 24.5 deg x 62.5 deg, but response rate was suppressed if the stimuli were superimposed on horizontally moving patterned backgrounds. Mantises also displayed appetitive behaviors to moving black squares (edge lengths = 10-47 deg) that moved in predetermined "erratic" paths; however, their response rates were affected by several factors: (1) response rate declined as edge length increased over 10 deg; (2) striking was emitted to stimuli viewed from 23 mm (but not farther) away; and (3) both stimulus displacement rate (distance moved between video frames) and apparent speed (video frame rate) dramatically affected the releasing strength of the stimuli. Finally, mantises responded appetitively to random dot patterns moving synchronously against identically patterned backgrounds and to pairs of black squares moving synchronously against a white background. However, in the latter case, response rate declined as the squares were moved farther apart horizontally or vertically. These and previous results from our laboratory on mantises are congruent with behavioral results obtained from other insects such as flies (Diptera) and dragon flies (Odonata) and suggest that there are neuroanatomical similarities between these groups.

Animals↗
PubMed1997

Effects of repeated disorientation on the acquisition of spatial tasks in rats: dissociation between the appetitive radial arm maze and aversive water maze.

This study examined the effects of disorientation on the acquisition of different spatial reference memory tasks. In an appetitively motivated radial arm maze task in which 1 arm was consistently baited, rats that were disoriented before each trial were impaired in their ability to acquire the task relative to rats placed in a clear container and not disoriented. However, disoriented rats were able to learn a Morris water maze and a water version of the radial arm maze under similar training conditions, suggesting that the effects of disorientation may interact with the quality or quantity of motivation involved in a given task. These results suggest that appetitive and aversive spatial tasks are dissociable, and that any impairment that is due to disorientation is specific to the appetitive radial arm maze task.

Animals↗
PubMed1988

Induction of an appetite for sodium in rats that show no spontaneous preference for sodium chloride solution--the Fischer 344 strain.

Fischer 344 rats show no spontaneous preference for isotonic sodium chloride (NaCl) solution. These experiments indicate, however, that a strong appetite for this solution may be induced by various methods, including adrenalectomy, administration of a mineralocorticoid hormone, acute depletion of sodium, and treatment with inhibitors of the angiotensin I converting enzyme (ACE). These treatments were also shown to produce the expected changes in the renin-angiotensin-aldosterone system, which thus appears to be involved in the induction of an appetite for NaCl solution in this strain of rat. The intakes of NaCl induced in the Fischer 344 rats by these experimental paradigms are less than those that have been reported in either Sprague-Dawley or Wistar strains in similar paradigms. In the case of sodium depletion, the intake of NaCl solution by Fischer 344 rats appears to be more closely related to the deficit than in the other two strains. Thus, the Fischer 344 strain of rats may be a particularly good model for studies of need-related sodium appetite.

Adrenalectomy↗
PubMed1988

Characteristics of thirst and sodium appetite in mice (Mus musculus).

The intakes of water and sodium chloride (NaCl) solution were examined in mice following treatment with agents that either stimulate or mimic various components of the renin-angiotensin-aldosterone system. Injections of either angiotensin II (Ang II) or isoproterenol produced very little water intake compared with the robust responses to either intracellular dehydration or to extracellular dehydration induced by treatment with polyethylene glycol (PEG). In studies on appetite for NaCl solution, mice exhibited no spontaneous preference for 0.15 M NaCl solution over water and did not change this preference during treatment with deoxycorticosterone acetate (DOCA), a sodium-deficient diet, or after adrenalectomy. Plasma concentrations of aldosterone were increased in intact mice fed a sodium-deficient diet but were not eliminated by adrenalectomy. However, acute treatment with furosemide in combination with a sodium-deficient diet stimulated an appetite for NaCl solution. Chronic oral administration of an angiotensin I (Ang I) converting enzyme inhibitor failed to induce a NaCl appetite. These findings show that mice are refractory to the induction of either water or NaCl intake by stimuli of the renin-angiotensin-aldosterone system, stimulation that is highly effective in rats; this suggests that there may be major differences among rodents in the hormonal determinants of behaviors related to hydromineral homeostasis.

Angiotensin II↗
PubMed1990

Preoptic angiotensin and salt appetite.

Two experiments were designed to test whether angiotensin (ANG) synthesis or receptor activation in the ventral preoptic region is critical for ANG-induced salt appetite in rats. In Experiment 1, infusions of ANG into the subfornical organ (SFO) produced water drinking without saline intake, but infusions near the organum vasculosum laminae terminalis (OVLT) produced both water and saline drinking. Thus, forebrain areas that support water drinking to ANG do not all support salt appetite. In Experiment 2, rats were given oral captopril (CAP) to enhance daily intake of water and saline solution by increasing ANG II synthesis in the brain. CAP microinjected into the SFO reduced CAP-enhanced water drinking without affecting saline intake, but CAP in the OVLT reduced enhanced saline intake without affecting water drinking. Thus, ANG acting in the OVLT, the most ventral part of the median preoptic nucleus, or other nearby structures is important for ANG-induced salt appetite.

Angiotensin II↗
PubMed1991

Effects of lesions of the ventral ventral median preoptic nucleus or subfornical organ on drinking and salt appetite after deoxycorticosterone acetate or yohimbine.

Lesions of the ventral ventral median preoptic nucleus (VVMnPO) enhanced daily salt appetite induced by subcutaneous (sc) injections of deoxycorticosterone acetate (DOCA) but did not affect acute salt appetite or water intake after sc injections of 5 mg/kg of the alpha-2-adrenoreceptor blocker yohimbine. Lesions of the subfornical organ (SFO) or its rostral fiber pathways had no effect on fluid intakes during DOCA treatments but significantly reduced water intake after yohimbine. These findings extend those of a previous report (Fitts, Tjepkes, & Bright, 1990) of enhanced DOCA-induced saline intake in VVMnPO-lesioned rats and demonstrate that the effect is specific to lesions of the VVMnPO. The mechanism of the thirst and salt intake elicited by yohimbine is still unclear, but the SFO and its fiber pathways appear to be important for the expression of the water drinking component. Neither lesion reliably affected yohimbine-induced salt appetite.

Animals↗
PubMed1993

Using signaled barpressing tasks to study the neural substrates of appetitive and aversive learning in rats: behavioral manipulations and cerebellar lesions.

The development of standard within-subject conditioning tasks for studying similarities and differences in the neural substrates of appetitive and aversive learning is described. Rats learned to press a bar during a brief tone presentation to receive a food pellet reward (the appetitive task). Using the same tone signal, conditioning chamber, and trial timing parameters, the same rats were then trained to press the bar during the tone presentation to avoid a mild footshock (the aversive task). As an initial study of the neural substrates of these forms of learning, the involvement of the cerebellum was assessed. Bilateral lesions of the deep cerebellar nuclei prevented the learning of the aversive task but had no effect on the learning of the appetitive task.

Animals↗
PubMed1996

Dissociations between appetitive and consummatory responses by pharmacological manipulations of reward-relevant brain regions.

Appetitive behaviors of rats were monitored in a runway situation following central infusions of neuroactive substances into brain areas implicated in electrical self-stimulation. Microinjections of the dopamine antagonist cis-flupentixol or the cholinergic antagonist atropine into the nucleus accumbens (Acb) severely reduced the approach speed and anticipatory shuttlebox activity while leaving the consumption of the 20% sucrose reward intact. Microinjections of GABA into the ventral tegmental area (VTA), pedunculopontine tegmental nucleus (PPTg), and oral pontine reticular nucleus (PnO) also severely disrupted approach without decreasing consumption. The highest doses of atropine into the VTA, PPTg, and PnO disrupted both consummatory and approach responses equally. The results indicate that modulation of various neurochemistries along the trajectory of the self-stimulation system has stronger effects on appetitive approach than consummatory motivation. The implications for understanding appetitive-approach motivation in the brain are discussed.

Acetylcholine↗
PubMed2006

The effects of deoxycorticosterone-induced sodium appetite on hedonic behaviors in the rat.

The authors tested the hypothesis that chronic treatment with a dose of deoxycorticosterone acetate (DOCA) known to elicit a robust sodium appetite can negatively affect the hedonic state of rats. Daily treatment with DOCA with no opportunity to ingest saline produced a rightward shift in the midpoint (effective current 50) of lateral hypothalamic self-stimulation (LHSS) current-response functions and reduced intakes of a palatable sucrose solution. Providing rats with 0.3 M saline during DOCA treatment prevented the rightward shift in LHSS response functions and the decrease in sucrose intake. The authors concluded that a chronic sodium appetite, with no opportunity to attenuate the appetite, can elicit a reduced responsiveness to reward.

Animals↗
PubMed1981

Thirst and sodium appetite after colloid treatment in rats.

Subcutaneous injection of polyethylene glycol (PEG) solution produced a progressive sequestration of extracellular fluid at the injection site. Appropriately, PEG-treated rats showed both thirst and sodium appetite. However, water intake began within 1 to 2 hr after the injections, whereas consumption of NaCl solution did not start until 3-4 hr later. Then rats ingested both fluids alternately until plasma volumes were restored, whereupon saline intake became even more prominent while water was consumed due to induced osmoregulatory needs. These three phases were seen regardless of the dose of PEG that was administered or the concentration of saline that was available. In contrast, after maintenance on a sodium-deficient diet for 2-4 days, or after bilateral adrenalectomy, rats increased their intake of saline immediately after PEG treatment. These and other findings suggest that the delayed onset of sodium appetite after PEG treatment that occurs when rats are maintained on standard sodium-rich chow results from the buffer provided by surplus extracellular fluid in those animals. They further suggest that sodium appetite is not directly associated with decreases in plasma volume or sodium concentration but instead may be stimulated by decreased availability of sodium in the brain.

Animals↗
PubMed1999

High and low carbohydrate and fat intakes: limits imposed by appetite and palatability and their implications for energy balance.

This report examines several issues concerning the effects of dietary fats and carbohydrates (CHOs) on body weight and the limits set on the intake of these nutrients by factors influencing appetite control: (i) the physiological relationship between feeding behaviour (FB) and body weight; (ii) the distribution of nutrients in Western foods and the implications this may have for FB; (iii) the contribution of nutrients in the diet, to total EI under both extreme and typical Western conditions; (iv) the known effects that fats, CHOs and dietary energy density (ED) exert on appetite and energy balance (EB); (v) the potential role of sensory factors in promoting or limiting fat, CHO and energy intakes (EI) in modern human populations Population studies and large surveys have identified individuals with wide ranges of fat and CHO intakes. Intakes of fat can vary from an average of 180 g/day to 25 g/day in a representative sample. But on individual days fat intake can rise to well over 200 g according to a selection of high fat foods. In a single meal, people can consume an amount of fat greater than the population daily average. From this analysis it can be deduced that the appetite control mechanism will permit the consumption of large amounts of fat (if an abundance of high fat foods exist in the food supply). Except for specific physiological circumstances (e.g. endurance explorers) where there is an urgent need for EIs, in the face of decreasing body weight, it is unlikely that the body will generate a specific drive for fat. Because CHO foods have a lower ED than fat foods (on average) and because of their greater satiating capacity, the free intake of high CHO foods is likely to be self-limiting (at lower EIs than those generated by fatty foods). This does not mean that excess EIs are impossible when people feed ad libitum on high CHO diets.

Appetite↗