Hypothalamic neuropeptide Y, galanin, and amines. Concepts of coexistence in relation to feeding behavior.
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Animals↗
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Activity of an identified histaminergic neuron, and its possible role in arousal of feeding behavior in semi-intact Aplysia.
The possible functions of histaminergic neuron C2 were studied in an isolated head preparation from which it was possible to obtain intracellular recordings while the buccal mass exhibited feeding-like responses. Application of food to the lips of the isolated head preparation elicited rhythmic buccal movements that appeared to be ingestion responses, since they moved seaweed into the buccal cavity and towards the esophagus, and their frequency and regularity was similar to the ingestion responses studied in a group of intact animals. The ingestion responses of the buccal mass consisted of 2 main phases of movement of the radula from a middle rest position: forward and return to rest, and backward and return to rest. The relative magnitudes and timing of these 2 phases were variable. Intracellular recordings from C2 in the isolated head revealed that C2 is silent when the buccal mass is quiescent, but that it can be excited into spike activity, either by mechanical stimulation of the perioral zone or by chemostimulation that results in rhythmic movement. C2 fires a burst of spikes in phase with each protraction-retraction cycle, and, if the movements continue, C2 fires even when the eliciting stimulus has been removed. Activity of the cell was usually preceded by fast depolarizing responses that appeared to be blocked axon spikes. The evidence suggests that C2 is part of a positive feedback loop that may help maintain the persistence of arousal of feeding behavior beyond the time that food stimuli are removed.
Animals↗
Norleucine: a branched-chain amino acid analog affecting feeding behavior of rats.
Norleucine, an isomer of leucine and isoleucine and a potent competitor of large neutral amino acid transport into brain, thereby depleting certain amino acid pools, was tested for its effects on growth and feeding behavior of rats fed an amino acid diet limiting in leucine. Growth and food intake were depressed in proportion to the dietary level of norleucine (0.2 to 1.1% of the diet). With suboptimal amounts of indispensable amino acids, leucine at 150% of the requirement reversed the effects of 0.2 and 0.5% norleucine; slight excesses of the other indispensable amino acids were required with extra leucine for maximum growth with 1.1% norleucine. Rats almost exclusively preferred the control to the norleucine diet, but not if the latter diet also contained leucine. Rats also strongly selected a nonprotein rather than norleucine diet when this was the first available choice. If the first choice was between the nonprotein and control diets, rats later almost exclusively selected the norleucine-containing rather than the nonprotein diet for varying periods (2 to 6 days). These studies suggest that amino acid analogs may be useful agents in the study of animal behavior associated with changes in brain amino acid pools.
Amino Acids↗
Central nervous system cholecystokinin and the control of feeding behavior in sheep.
There is increasing evidence that brain cholecystokinin (CCK) peptides function as neuropeptide signals of satiety. Injection of as little as femtomole amounts of CCK-8 into the cerebral ventricles selectively decreased feeding in sheep, and other species (chicken, pig, hamster and rat) also decrease feeding in response to CNS injections of CCK. As would be expected with a physiological satiety agent, CCK-8-induced suppression of feeding interacts in a corrective manner with the energy deficit of the animal, in that the longer the fasting period, the greater the amount of CCK-8 required to suppress feeding. Although it has not been possible to measure changes in concentration of CCK in cerebrospinal fluid (CSF) with feeding, neutralization of endogenous CCK by administration of CCK antisera into the CSF delayed satiety in sheep. This and other evidence not only supports a physiological role for endogenous brain CCK in feeding behavior, but also suggest that CSF transports CCK to site(s) of action. Little is known of CCK's mechanisms of action, but because CNS CCK also causes changes in both gut motility and secretion of insulin and glucagon, the satiety could result directly from effects on behavior, and indirectly through metabolic changes. Evidence of selective uptake of CCK from CSF suggested involvement of hypothalamic periventricular areas in these functions. Recent findings in sheep of a 60% decrease in CCK content in anterior hypothalamus two hrs after a meal also supports this hypothesis.
Animals↗
Flooring in front of the feed bunk affects feeding behavior and use of freestalls by dairy cows.
In 2 experiments we assessed how preferences, time budgets, and feeding behavior of dairy cows change in response to flooring surfaces in front of the feed bunk. In Experiment 1, 12 nonlactating dairy cattle were individually housed with access to 2 standing platforms filled with either concrete or sawdust. In Experiment 2, 24 nonlactating dairy cattle were given access to either concrete or Animat rubber flooring in front of the feed bunk. In Experiment 1, cows preferred the sawdust to the concrete flooring. In both experiments, cows provided with a softer floor in front of the feed bunk spent more time standing near the feed bunk without eating (Experiment 1: 67 vs. 40 min/d on sawdust vs. concrete, respectively, SEM = 5.6 min/d; Experiment 2: 176 vs. 115 min/d on Animat vs. concrete, respectively, SEM = 20.5 min/d) compared with when they were kept on concrete. The increased time spent at the feed bunk was due to a combination of more frequent eating and standing bouts, indicating that cows were more willing to move on nonconcrete flooring. Total time spent eating was significantly greater on the softer floor in Experiment 2, but not in Experiment 1 (Exp. 1: 289 vs. 275 min/d on sawdust and concrete, respectively, SEM = 7.3 min/d; Exp. 2: 330 vs. 289 min/d on Animat and concrete, respectively, SEM = 15.4), although feed intake was increased on the sawdust treatment in Experiment 1. Cows spent significantly more time lying in the feed alley when the flooring was rubber (219 vs. 53 min/d on Animat and concrete, SEM = 53.6 min/d), perhaps because the lying area in Experiment 2 was inadequate. In conclusion, cows prefer to stand on softer flooring in front of the feed bunk, and are more willing to move on and spend more time standing in front of the feed bunk when provided with softer flooring. These results indicate that cows find softer flooring surfaces more comfortable to stand on than concrete, and highlight the importance of evaluating the comfort of the entire facility.
Animal Welfare↗
Neuroestrogenic control of feeding behavior and body weight in rats with kainic acid lesions of the lateral septal area.
The role of the lateral septal area (LS) in the regulation of energy balance and the estrogenic control of feeding behavior in the female rat has been examined. Food intake (FI) and body weight (BWt) were measured daily following kainic acid (KA) LS lesions (KALS) to assess any regulatory changes in energy balance. In all animals KA lesions of the LS produced major cell loss in the LS; however the extent of damage was variable. Associated with KA lesions of the LS was the concurrent loss of CA3-CA4 cell groups in the hippocampus which was comparable for all the lesioned animals. The extent of septal damage was quantified morphometrically and correlated with changes in FI and BWt following estrogen treatment. The significant effects of the KALS lesions, relative to the control animals were: an increase in BWt which was statistically significant 22 days following brain surgery, an increase in daily FI which was significant by day 6 post surgery, an attenuation in the anorexic effects of estrogen on FI and BWt, and a significant decrease in the present days of vaginal estrus. Moreover, the anorexic effects of estrogen were significantly correlated with the extent of LS damage, but not the amount of hippocampal damage. The present study confirms that an increase in BWt is produced by KA lesions of the LS and further indicates that a sustained period of increased FI precedes the increase in BWt.(ABSTRACT TRUNCATED AT 250 WORDS)
Animals↗
Effects of neuropeptide Y (NPY) and [D-Trp32]NPY on monoamine and metabolite levels in dialysates from rat hypothalamus during feeding behavior.
Administration of neuropeptide Y (NPY) into hypothalamic areas or into the cerebral ventricles induces marked increases in food consumption in satiated rats. Since monoamines have been suggested to be involved in NPY-induced feeding, we investigated the effects of NPY and [D-Trp32]NPY, a putative NPY antagonist, on extracellular levels of norepinephrine (NE), dopamine (DA), serotonin (5-HT), 3,4-dihydroxyphenyl acetic acid (DOPAC), homovanillic acid (HVA) and 5-hydroxyindole-3-acetic acid (5-HIAA) in the hypothalamus, including the paraventricular hypothalamic nuclei (PVN), during feeding behavior. Intracerebroventricular (i.c.v.) injections of NPY (20 microg) significantly increased extracellular NE (1.5-fold), DA (2.5-fold), DOPAC (2-fold) and HVA (3-fold), and did not change 5-HT or 5-HIAA levels. This dose of NPY significantly increased food intake over a 2 h period. The putative NPY antagonist [D-Trp32]NPY (40 microg, i.c.v.) produced similar neurochemical changes to NPY: it increased dialysate levels of NE (1.7-fold), DA (2.5-fold), DOPAC (1.6-fold) and HVA (2.2-fold) and did not change 5-HT or 5-HIAA levels. [D-Trp32]NPY also produced a significant increase in food intake. I.c.v. administration of [D-Trp32]NPY 5 min before NPY did not significantly change the increase in NE, DA, HVA and DOPAC induced by NPY. In these animals, food consumption was also significantly increased. These data indicate that NPY-induced feeding is associated with activation of the hypothalamic monoaminergic system and that [D-Trp32]NPY, at the dose given, acts as an agonist and not as an antagonist at NPY receptors in vivo.
3,4-Dihydroxyphenylacetic Acid↗
The significance of apical K+ channels in mudpuppy feeding behavior.
Behavioral experiments were conducted to determine the effects of known potassium channel blockers, minnow extract (a natural food substance), and other taste stimuli on feeding behavior in the mudpuppy (Necturus maculosus). Groups of 10-15 mudpuppies were presented with one or more of the following chemicals dissolved in gelatin cubes: H2O (control), NaCl (1.0 M; 0.2 M), crude minnow extract (0.1 g/ml), CaCl2 (1.0 M), citric acid (0.1 M; pH 2, 0.01 M; pH 3), quinine HCl (0.1 M), tetraethylammonium chloride (TEA; 0.1 M), KCl (1.0 M) and an amino acid mixture containing L-phenylalanine, L-arginine, L-histidine, L-valine, L-glutamic acid and L-lysine at concentrations of 0.02 M and 0.04 M each. Crude minnow extract was centrifuged and separated into components consisting of the following fractions: > 500 D, > 1000 D and > 14,000 D, each of which was presented to mudpuppies in cubes. Results were expressed as the percentage of animals rejecting the cube within 5 min of taking the cube into the oral cavity. Statistical analysis using the Fisher exact test indicated that cubes containing chemicals known to block (CaCl2, TEA, citric acid and quinine) or permeate (KCl) apical K+ channels in mudpuppy taste cells were more aversive than control cubes, and aversion was concentration-dependent. In contrast, cubes containing minnow extract and components of minnow extract < 14,000 D were significantly preferred over control cubes. Cubes containing a mixture of minnow extract and an aversive chemical were significantly less aversive than cubes containing only an aversive chemical. These findings suggest that activation of the apical K+ conductance in mudpuppy taste cells triggers an aversive response, but the aversion can be ameliorated by low molecular weight compounds present in minnow extract.
Amino Acids↗
Fibroblast growth factor inhibits locomotor activity as well as feeding behavior of rats.
The effects of acute and chronic intracerebroventricular (i.c.v.) administration of basic fibroblast growth factor (bFGF) on behavior were examined in free-feeding rats. An i.c.v. injection of bFGF induced behavioral changes, such as an increase in resting and decreases in grooming, moving, and food intake at a dose of 20 or 50 ng. These effects appeared at 4-5 h and lasted at least 11 h after the injection. These changes, as well as inhibition of body weight gain, were also found during a 6-day period of chronic i.c.v. infusion of bFGF at a dose of 20 ng/h. These results indicate that bFGF as both bolus i.c.v. injection and chronic i.c.v. infusion inhibits not only feeding behavior but also locomotor activity in rats. It is suggested that the inhibitory effect of bFGF on food intake may be in part ascribed to the suppression of behavior by bFGF.
Animals↗
Long-term lateral hypothalamic single unit analysis and feeding behavior in freely moving rats.
Lateral hypothalamus activity was observed in 23 single units for more than 24 h each in freely moving rats. The activity of 3 neurons was circadian related: low in the day and high at night. Ten neurons responded with inhibition related to individual feeding acts. These two neuron types might be important for long-term feeding rhythm and short-term feeding behavior.
Animals↗
Fish mercury bioaccumulation as a function of feeding behavior and hydrological cycles of the Rio Negro, Amazon.
The acidic black waters of the Rio Negro are unimpacted by anthropogenic sources and yet, are characterized by fish containing relatively high Hg concentrations. Regular annual flooding alters the aquatic environment, thereby affecting fish feeding strategies. We studied the impact of annual flooding on fish-Hg bioaccumulation. Tucunarés (Cychla spp, carnivorous), Peixe-cachorro (Hydrolycus scomberoides, carnivorous), Traíra (Hoplias malabaricus, carnivorous), Piranha-branca (Serrasalmus aff. eigenamanni, carnivorous), Piranha-preta (Serrasalmus rhombeus, carnivorous), Acará (Acarichthys heckellii, omnivorous), Aracú (Leporinus friderici, omnivorous), Orana-preta (Hemiodus unimaculatus, omnivorous), Sardinha (Triportheus elongatus, omnivorous), Branquinha (Potamorhina latior, detritivorous), Jaraqui-escama-fina (Semaprochilodus taeniurus, detritivorous), and Pacú-branco (Myleus torquatus, herbivorous) were studied during high (July) and low waters (February) and categorized by body mass. Regardless of hydrological period, ranges of total-Hg concentrations were higher for carnivorous than for omnivorous, detritivorous and herbivorous species. Some species (Traíra, Sardinha, Peixe-cachorro, Piranha branca, Piranha preta) showed changes in feeding patterns as indicated by an inverse trend of Hg bioaccumulation with season. Species with similar trends of Hg bioaccumulation showed higher Hg concentrations during the flooded season (Aracú, Pacú branco and Orana preta) and some had lower Hg (Acará, Branquinha and Tucunarés). Fish Hg concentration is species specific and reflects changes in feeding-behavior dominance brought by annual inundation.
Animals↗
Effect of chronic intake of sweet substance on nociceptive thresholds and feeding behavior of Rattus norvegicus (Rodentia, Muridae).
The investigation of the influence of sweetened food on feeding behavior targeted to non-sucrose nutrients as well as the sensitivity to painful stimuli in isolated and grouped animals is the aim of the present work. The tail withdrawal latencies in the tail-flick test (a spinal reflex) were measured before and immediately after the treatment with tap water or sucrose (62, 125 or 250 g/l). Our findings suggest that: (a) The analgesic effect of sucrose intake depends on the concentration of sucrose solution and on the time during which the solution is consumed; (b) the most effective concentration of sucrose followed by antinociceptive effect was the one of 250 g/l in both isolated and grouped animals; (c) considering the individually caged rats, the intake of sucrose in the highest concentration (250 g/l) was the smallest as compared with the consumption of sucrose in more diluted solutions (62.5 and 125 g/l), but this higher sweetened solution was followed by antinociception; (d) animals treated with concentrated sucrose solution ate smaller quantities of pellets than animals treated with tap water; (e) tonic intake of highly concentrated sweet substance seems to be crucial for the increase of the nociceptive threshold in our model of sweet substance-induced antinociception.
Analgesia↗
The effect of digitoxose on feeding behavior.
The effect of digitoxose (DIG) on food intake, gold thioglucose (GTG) lesion formation in the ventromedial hypothalamus (VMH), and VMH glucose oxidation in vitro was investigated in mice. DIG significantly decreased the amount of food ingested during the day compared to controls (p less than 0.01). DIG had no effect on nocturnal feeding. GTG lesion formation in the VMH and VMH glucose oxidation were not altered by DIG treatment. These results suggest that DIG alters daytime feeding behavior by affecting extrahypothalamic or peripheral glucoreceptor sites.
Animals↗
Influence of housing conditions on the effects of serotonergic drugs on feeding behavior in non-deprived rats.
Serotonin plays an important role in the regulation of food and water intake, and drugs that inhibit the uptake of this neurotransmitter have been used as appetite suppressors. As the clinical usage of anorectics necessarily involves chronic drug administration, the effects of chronic treatment in animals are likely to be of greater clinical relevance than acute drug effects. Besides, little effort has been made to examine whether these effects interact with stressful situations, such as isolation. We have therefore examined the effects of fluoxetine, a selective 5-HT reuptake inhibitor, and gepirone, a 5-HT1A agonist, on body weight in isolated and in group-housed rats during 3 weeks of daily treatment. Gepirone caused an increase in body weight only in isolated rats. On the other hand, fluoxetine caused a significant reduction in body weight in both singly- and group-housed animals. The effects of these serotonergic agents were more prominent during the first week of treatment. From the data obtained in this study, it is suggested that increased 5-HT transmission produced by fluoxetine during chronic administration seems to be crucial for the appetite-regulating action of 5-HT, and this hypophagic effect does not seem to be dependent on the activation of 5-HT1A receptors since it was not shared by gepirone. Moreover, a concomitant stressful situation, such as isolation, interferes with the action of gepirone on feeding behavior. The hyperphagic effects of chronic regimen with gepirone in isolated animals are probably due to the concurrent reduction of the 5-HT transmission caused by this anxiogenic condition at the earlier stages of treatment. On the other hand, the anorectic effects of fluoxetine do not seem to interact with the stressful situations caused by isolation.
Animals↗
Mechanism for food avoidance learning in the central pattern generator of feeding behavior of Pleurobranchae californica.
Food-avoidance conditioning in the mollusk Pleurobranchaea results in suppression of the feeding response to food stimuli. In conditioned animals, identified interneurons of the central pattern generator (CPG) for feeding behavior, the Int-2s, respond to a food stimulus with greater and more long-lasting excitation than controls. Enhanced Int-2 responsiveness to food stimuli is associated with markedly heightened Int-2 excitability. Sustained activity in the Int-2s arrests motor output of the oscillatory CPG in the protraction/retraction movement cycle of feeding through tonic excitation of a population of retractor interneurons and inhibition of protractors. The CPG locus of the learning mechanism is permissive of sensory excitation of alternative behavior and leaves the possibility open for release of the suppressed behavior in a fully aroused state.
Journal Article↗
Structure-activity relationship of linear tetrapeptides Tic-DPhe-Arg-Trp-NH2 at the human melanocortin-4 receptor and effects on feeding behaviors in rat.
The melanocortin subtype-4 receptor (MC4R) has been implicated in the control of feeding behavior and body weight regulation. A series of tetrapeptides, based on Tic-DPhe-Arg-Trp-NH2-a mimic of the putative message sequence "His-Phe-Arg-Trp" and modified at the DPhe position, were prepared and pharmacologically characterized for potency and selectivity. Substitution of His with Tic gave peptides with significant increases in selectivity. The effects of the substitution pattern of DPhe were investigated and it has significant influences on potency and the level of the maximum cAMP accumulation. Intracerebroventricular administration of peptide 10 induced significant inhibition of cumulative overnight food intake and feeding duration in rats.
Animals↗
Larval feeding behavior of three co-occurring species of container mosquitoes.
Interspecific differences in foraging behavior may help to determine whether the outcome of interspecific competition is coexistence or exclusion. Mosquitoes in the genus Culex are commonly described as foraging primarily by filtering the water column. This behavior contrasts with that of other container-dwelling genera, such as Aedes and Ochlerotatus, that are thought to forage primarily by browsing on container and detritus surfaces. We compared the feeding behavior of Cx. pipiens, Ae. albopictus, and Oc. triseriatus in a laboratory experiment in which we monitored behavior of individual mosquitoes in two different food environment treatments: food suspended in the water column only and food attached to leaf surfaces only. For each mosquito in each food environment, we quantified the time allocated by larvae to one of four positions and to one of three activities. The effect of treatment was significant, with individuals in Fluid Only environments spending more time resting-filtering at the surface, and individuals in Leaf Only environments spending more time browsing on walls. There were significant differences among species, with Cx. pipiens spending more time at the surface than the other species, which spent more time thrashing below the surface. There was no significant interaction of species and treatment, indicating that all three species modify their behavior in similar ways in these environments. Contrary to current understanding, our data suggest that Cx. pipiens browse as frequently as do these potential competitors but show a greater concentration of foraging effort at the top of a container.
Aedes↗
The effect of ingesting olestra-based foods on feeding behavior and energy balance in humans.
This article reviews currently published works on the effects of olestra on appetite and energy intake (EI) in humans. To date 24 studies have examined the impact of olestra-containing foods on aspects of feeding behavior, which are published in 20 reports. The general response of human subjects to olestra-based decreases in dietary energy density (ED) is either poor caloric compensation or partial (nonmacronutrient specific) increases in EI. Averaging the degree of energy compensation across 22 studies gives a value of 27% (nonweighted mean). In studies where compensation occurred, fat intake but not EI was reduced. These effects appear to occur in both lean and obese, men and women and under a variety of conditions ranging from the laboratory to real life. However, all but two of these studies were short term. One study suggests that in subjects to whom weight loss is desirable these deficits can persist for up to 3 months. Subjects with no wish to lose weight may compensate better over longer periods. In another 3-month study, ingestion of olestra-based foods did not induce energy deficits but limited the significant weight gain seen on a full-fat control. The longer term effects of olestra on body weight requires further investigation. There is evidence that restrained eaters tend to eat slightly more of olestra-based foods if they know that they are reduced in fat and energy. This is probably a general response to low-fat foods rather than to olestra per se. The fact that olestra-based foods have the potential to provide the sensory qualities of real fat suggests that these foods may be particularly effective in habitual high-fat consumers with a sensory preference for dietary fat.
Adult↗