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PubMed2004

Effects of bird age, density, and molt on behavioral profiles of two commercial layer strains in cages.

Two commercial strains, Hy-Line W-36 and DeKalb XL, were moved to a laying house at 18 wk of age. They were housed 6 hens/layer cage at 2 densities (361 and 482 cm2/bird) with 2 replications each per strain/density combination. The high-density treatment contained 24 hens/replication and the low-density treatment contained 18 hens/replication for a total of 168 hens. Production parameters were measured during the first egg production cycle, the molt period, and the first 4 wk of the second lay cycle (20 to 68 wk of age). Behavioral observations were taken during 2 consecutive d at 26, 34, 43, 51, 62, 64, and 68 wk of age to examine behavioral patterns. Modified Hansen's tests were conducted concurrently to provide indication of the fearfulness levels of hens at the various stages of production. The production characteristics were similar for both strains. The hens kept at the higher density had lower (P < 0.01) hen-day production and (P < 0.05) daily egg mass. Appetitive behaviors were not affected by strain or density but were affected by the age of the hen and by molting. During the molt, feeding and drinking behavioral acts were fewer (P < 0.05) at 0.018 and 0.013 acts per bird/min, respectively, and standing behavior was highest. The results indicated that the frequencies of pecking inedible objects during the molt period were similar to the frequencies at 26 and 34 wk. Hens performed more acts of standing, and crouching and had lower frequency of movement during the molt. Those kept at a low density performed more movement acts. Feather pecking decreased as hens aged and increased when they molted but was not affected by strain or density. The frequency of aggression and submissive acts was significantly lower during the molt period. Behaviors were affected by strain, density, bird age, and molting; however, the patterns and number of aggressive acts did not increase to compromise the welfare status of the hens. Behaviors during the molt appeared consistent with mechanisms for conservation of body reserves.

Age Factors↗
PubMed1981

Vagal mechanisms in appetite regulation.

Though the importance of the vagal nerve for appetitive behavior has been known for a decade, with extensive studies of vagal physiology being performed since the end of the last century, it has not been until recently that major progress has been made in elucidating some of the vagal mechanisms involved in food intake. This short review summarizes methods for studying vagal function, vagal transmission and physiological vagal effects important for appetite regulation normally and in relation to hypothalamic function. Particular emphasis is placed on effects of vagotomy on body weight.

Appetite Regulation↗
PubMed2004

Peripheral ghrelin injections stimulate food intake, foraging, and food hoarding in Siberian hamsters.

Fasting triggers many effects, including increases in circulating concentrations of ghrelin, a primarily stomach-derived orexigenic hormone. Exogenous ghrelin treatment stimulates food intake, implicating it in fasting-induced increases in feeding, a consummatory ingestive behavior. In Siberian hamsters, fasting also stimulates appetitive ingestive behaviors such as foraging and food hoarding. Therefore, we tested whether systemic ghrelin injections (3, 30, and 200 mg/kg) would stimulate these appetitive behaviors using a running wheel-based food delivery system coupled with simulated burrow housing. We also measured active ghrelin plasma concentrations after exogenous ghrelin treatment and compared them to those associated with fasting. Hamsters had the following: 1) no running wheel access, free food; 2) running wheel access, free food; or 3) foraging requirement (10 revolutions/pellet), no free food. Ghrelin stimulated foraging at 0-1, 2-4, and 4-24 h postinjection but failed to affect wheel running activity not coupled to food. Ghrelin stimulated food intake initially (200-350%, first 4 h) across all groups; however, in hamsters with a foraging requirement, ghrelin also stimulated food intake 4-24 h postinjection (200-250%). Ghrelin stimulated food hoarding 2-72 h postinjection (100-300%), most markedly 2-4 h postinjection in animals lacking a foraging requirement (635%). Fasting increased plasma active ghrelin concentrations in a time-dependent fashion, with the 3- and 30-mg/kg dose creating concentrations of the peptide comparable to those induced by 24-48 h of fasting. Collectively, these data suggest that exogenous ghrelin, similar to fasting, increases appetitive behaviors (foraging, hoarding) by Siberian hamsters, but dissimilar to fasting in this species, stimulates food intake.

Animals↗
PubMed2005

Neuro-hormonal control of food intake: basic mechanisms and clinical implications.

Obesity is one of the most common metabolic diseases and the greatest threats of the health because of possibility of numerous complications. In order to design effective drugs or apply the helpful surgical procedure it is essential to understand physiology of appetite control and pathophysiology of obesity. According to the first law of thermodynamics, the energy input in the form of food, equals energy expenditure through exercise, basal metabolism, thermogenesis and fat biosynthesis. The control of body weight actually concerns the control of adipose tissue with the key role of hypothalamus, possessing several neuronal centers such as that in lateral hypothalamic nuclei considered to be "hunger" center and in ventromedial nuclei serving as the "satiety" center. In addition, paraventricular and arcuate hypothalamic nuclei (ARC) are the sites where multiple hormones, released from the gut and adipose tissue, converge to regulate food intake and energy expenditure. There are two distinct types of neurons in ARC that are important in control of food intake; (1) preopiomelanocortin (POMC) neurons activated by an orexigenic hormones and releasing alpha-melanocyte-stimulating hormone (alpha-MSH) in satiety center and (2) neurons activated by orexigenic peptides such as ghrelin that release the substances including neuropeptide Y (NPY) and Agouti-Related Peptide (AgRP) in hunger center. ARC integrates neural (mostly vagal) and humoral inputs such as enteropeptides including orexigenic (ghrelin and orexins) and an orexigenic peptides (cholecystokinin, polypeptide YY, glucagon-like peptide-1, oxyntomodulin, leptin and others) that exert a physiological role in regulating appetite and satiety. The peripherally (gut, adipose tissue) and centrally expressed modulators of appetitive behavior act through specific receptors in the afferent (mostly vagal) nerves and hypothalamic neurons implicated in adiposity signaling and regulation of food intake.

Adiposity↗
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↗
PubMed1984

Behavioral patterns of Aplysia fasciata along the Mediterranean coast of Israel.

Aplysia fasciata were observed in a number of environments. They were usually aggregated. Animals were occasionally buried in sand. Aplysia were less mobile and more deeply hidden when waves were strong. Aplysia swam only in a calm environment. A wide variety of seaweeds were eaten, but the most common food was Ulva lactuca. Food arousal and satiation occur in the field. Often the pattern of feeding was a gradual slowing down and eventual cessation of eating; however, many meals deviated from this pattern. Appetitive behaviors preceding mating as a male were similar to those preceding eating. Aroused animals mated as males, while passive animals mated as females; mating as a male produced arousal, expressed as an increased likelihood to respond to food or to mate as a male. Two males could simultaneously impregnate one female. Animals mate in large groups, constantly changing partners. Mating groups occur in linear chain, branched chain, and closed chain configurations. Egg laying and egg masses were observed in areas inhabited by animals. Inking was never observed without exprimenter intervention, even when a crab attacked an Aplysia.

Animals↗
PubMed2005

The interoceptive cue properties of ghrelin generalize to cues produced by food deprivation.

A number of recent studies implicate the gut-brain peptide ghrelin as a putative "hunger signal". Most of these studies, however, rely on either consummatory behavior (in humans or nonhuman animals) or self-report (in humans) to draw conclusions regarding the orexigenic properties of this peptide. The present study employs the deprivation intensity discrimination paradigm to assess the interoceptive sensory properties of ghrelin in rats. In this paradigm, one group of rats was placed in a training context and presented with sucrose pellets when 24 h food deprived, but not when 1 h food deprived (24+ group). A second group was trained using the opposite sucrose-deprivation level contingency (1+ group). Learning in this paradigm was demonstrated by animals approaching the food delivery location more frequently under their rewarded compared to their non-rewarded deprivation condition (prior to actual pellet delivery). After asymptotic performance of this discrimination was achieved, these animals (1 h food deprived) were administered ghrelin or saline, either i.p. (3 or 6 nmol) or i3vt (0.1 or 1 nmol), placed in the training context, and appetitive responses were measured. Testing was conducted in extinction, eliminating confounding effects of food consumption. Results of these tests showed that 6 nmol i.p. ghrelin and 0.1 and 1 nmol i3vt ghrelin all generalized to a state of 24 h food deprivation, indicating that exogenous ghrelin has sensory properties in common with the stimuli produced by 24 h food deprivation. These results support the notion that endogenous ghrelin contributes to an interoceptive hunger cue, and that this may be a mechanism by which ghrelin influences food intake and appetitive behavior.

Animals↗
PubMed1998

Inhibition of eating behavior: negative cognitive effects of dieting.

This study tested the hypothesis that dieters would score higher than nondieters in terms of food rumination. Two hundred and thirty one college undergraduates completed the Eating Obsessive-Compulsiveness Scale (EOCS) and responded to a questionnaire that inquired about dieting status. Subjects also completed measures that tapped neuroticism and social desirability. Results showed that current dieters were significantly more obsessed with thoughts of eating and food than were nondieters. Neither dieting status nor EOCS scale scores were related to neuroticism or social desirability. These results are consistent with previous theory and research suggesting that inhibition of appetitive behaviors can have negative cognitive effects. Moreover, they indicate a potential target for therapeutic intervention.

Adolescent↗
PubMed1997

Initial manifestations of disordered eating behavior: dieting versus binging.

OBJECTIVE: We examined the onset of binge eating and dieting in 108 women with bulimia nervosa to determine whether (1) dieting always preceded binge eating; (2) dieting always preceded the onset of bulimia nervosa; and (3) individuals who manifested early initial binge eating differed from those whose earliest manifestation of disordered eating behavior was dieting in terms of lifetime psychopathology and temperament. METHOD: One hundred eight women were assessed at entry to a randomized clinical trial of cognitive-behavioral therapy for bulimia nervosa using structured diagnostic methodology. Retrospective recall of the onset of disordered eating behavior was used to categorize individuals as initial binge eaters or initial dieters. We then compared lifetime psychopathology and temperament across the two groups. RESULTS: Seventeen percent of women reported early binge eating prior to any dieting behavior. The mean age of onset of binging in this group was approximately 10 years. Neither the clinical picture of bulimia nervosa nor lifetime psychopathology differed between initial binge eaters and initial dieters. Individuals with early binge eating endorsed higher novelty seeking and lower harm avoidance. CONCLUSION: In a minority of women with bulimia nervosa, binge eating precedes dieting. These women display markedly higher novelty seeking and lower harm avoidance. Possible links between the dopamine system, novelty seeking, and appetitive behavior are discussed.

Adolescent↗
PubMed2006

Lipopolysaccharide and interleukin-1beta decrease sucrose intake but do not affect expression of place preference in rats.

Immune system activation has been shown to induce decreased interest in pleasurable stimuli. Studies of this phenomenon have assessed the effect of cytokines or lipopolysaccharide (LPS) on behavior maintained by primary reinforcers, stimuli, such as palatable solutions, that effectively reinforce behavior without prior training. The studies reported in this paper replicated findings of immune system activation decreasing intake of a palatable solution and assessed the effects of immune activation on behavior maintained by a conditioned reinforcer, a stimulus paired with a the palatable solution. Using a conditioned place preference procedure, the effects of LPS and interleukin-1beta (IL-1beta) on sucrose intake (primary reinforcer) and preference for a sucrose-paired environment (conditioned reinforcer) were tested. LPS and IL-1beta decreased sucrose intake but had no effect on the expression of a sucrose-induced place preference, indicating a differential effect of immune system activation on appetitive behaviors maintained by primary and conditioned reinforcers. Finally, it was shown that a sucrose-induced place preference is sensitive to the motivational state of the subjects at the time of testing; a sucrose-induced place preference was demonstrated if rats were tested when water deprived but not if tested after free access to water.

Animals↗
PubMed1982

The effects of chronic administration of naltrexone on appetite and water exchange in rats.

The effects of chronic administration of naltrexone (200 microgram/kg/hr) on appetitive behaviors and renal water and electrolyte excretions were studied in rats. Naltrexone reduced food and water intake, the renal excretions of water and electrolyte excretions were studied in rats. Naltrexone reduced food and water intake, the renal excretions of water and electrolytes, and osmolar clearance. No changes in plasma levels of electrolytes, plasma and urine Na+-K+ ratios, hematocrit ratio, plasma osmolality, the clearances of K+ and Na+, and the reabsorption of solute free water were found. The changes in appetite were compensated for by appropriate changes in renal excretions, resulting in no change in electrolyte balance or water exchange. These observations are discussed in relation to current theories of the role of endorphins in appetite control.

Animals↗
PubMedDate not supplied

The relationship between motor and secretory behaviors in classical appetitive conditioning.

Three hungry dogs received pairings of food with an accessible, illuminated panel. This resulted in the dogs' approaching the lighted panel and salivating. Despite the similarity of these conditioning procedures to those used in a large body of research primarily with avians, however, the dogs did not physically contact the lighted stimulus panel. These results bear on several issues concerning the form and direction of classically conditioned behaviors.

Animals↗
PubMed1999

The influence of serotonin depletion on rat behavior in the Vogel test and brain 3H-zolpidem binding.

The influence of p-chlorophenylalanine (p-CPA) and 5,7-dihydroxytryptamine (5,7-DHT)-induced serotonin depletion on rat behavior as well as on zolpidem's the behavioral effects and binding to some brain areas of zolpidem, was examined with the help of Vogel's punished drinking test and autoradiography, respectively. Moreover, changes in the serotonin levels and turnover rate were studied in the forebrain and brainstem of rats pretreated with various ligands at the benzodiazepine (BDZ) receptors (midazolam, bretazenil, abecarnil, zolpidem). These drugs were given at doses shown previously to significantly disinhibit animal behavior suppressed by punishment in the Vogel test (Nazar et al., 1997). It was found that serotonin decrease in the frontal cortex and hippocampus after p-CPA significantly and inversely correlated with rat behavior controlled by fear in the VT. p-CPA produced an anticonflict activity in the absence of effect on spontaneous drinking, pain threshold and motility of animals. All applied benzodiazepine receptor ligands decreased the 5-HT turnover rate in the frontal cortex and hippocampus, whereas in the brainstem only abecarnil and zolpidem diminished 5-hydroxyindoleacetic acid levels. This part of the study replicated earlier data with neurotoxins and indicated that the anxiolytic-like effect of 5-HT depletion in some models of anxiety did not depend on changes in animal appetitive behavior or stimulus control. Moreover, the fact that all nonselective and selective (zolpidem) agonists of the type 1 benzodiazepine receptors seemed to produce the same anticonflict effect and decreasing 5-HT turnover indicates that this subtype of benzodiazepine receptor may be important for the interaction between brain 5-HT and GABA/BDZ systems. Accordingly, it was found that serotonin decrease enhanced the anticonflict effect of zolpidem in the Vogel test and increased 3H-zolpidem binding to the occipital cortex and substantia nigra. Altogether, the present study provides more arguments for the role of changes in the activity of brain 5-HT innervation in the control of emotional processes. Moreover, it points to the BDZ1 receptor subtype as a possible target of interaction between brain 5-HT and GABA(A)/BDZ systems.

5,7-Dihydroxytryptamine↗
PubMed2004

Voluntary exercise augments acute effects of CB1-receptor inverse agonist on body weight loss in obese and lean mice.

Cannabinoid CB1 receptor (CB1R) inverse agonists reduce appetite and body weight (BW) gain in various species. Exercise is thought to be a natural reward process and the cannabinoid system is also believed to influence reward. We tested the hypothesis that voluntary exercise would augment the effects of AM251, a CB1R inverse agonist, on food intake (FI) and BW loss in murine genetic models of obesity. ob/ob, agouti yellow (A(y)), and lean C57BL/6J mice were treated via oral gavage with vehicle or AM251 (1, 3, or 10 mg/kg) 1 h before the dark cycle. The suppressive effects of 3 and 10 mg/kg AM251 on overnight FI, BW gain, and water intake (WI) were significant in ob/ob mice. In contrast, in A(y) mice, 10 mg/kg AM251 decreased FI and BW gain while it did not influence WI. Food consumption of ob/ob and A(y) mice, as evidenced by feeding frequency (FF) and feeding duration (FD), was reduced by AM251 for 4-6 h. AM251 at these doses had no impact on the appetitive behavior or BW gain of lean mice. After a 1-week wash-out period, mice were given running wheels in their home cages. With running wheel exercise, lean and obese mice exhibited increased sensitivity to AM251. Low voluntary wheel running activity of ob/ob mice precluded detection of combined effects of AM251 and exercise in this genetic model of obesity. Lean and agouti mice given AM251 combined with exercise lost a greater amount of BW than with AM251 alone. Our data suggest that voluntary exercise can enhance CB1R inverse agonist effects on appetite and BW loss in both lean and agouti obese mice.

Animals↗
PubMed1997

Norepinephrine microinjections in the hypothalamic paraventricular nucleus increase extracellular dopamine and decrease acetylcholine in the nucleus accumbens: relevance to feeding reinforcement.

Norepinephrine (NE) was microinjected into the paraventricular nucleus (PVN), while microdialysis was used to monitor extracellular dopamine (DA) and acetylcholine (ACh) in the nucleus accumbens (NAc). The PVN is a site where exogenously administered NE can act through alpha 2 receptors to elicit eating behavior and preference for carbohydrates. It was hypothesized that NE in the PVN acts on a behavior reinforcement system by altering the DA/ACh balance in the NAc. NE microinjections (80 nmol in 0.3 microliter), which effectively elicited feeding in satiated rats in a separate test, caused a significant increase in extracellular DA (109%) and decrease in ACh (-27%) when the same animals were tested in the absence of food. In contrast when the food was available and ingested, ACh increased (51%) instead of decreasing. These results support the hypothesis that a functional link exists between the PVN and the NAc in which DA helps initiate and ACh helps stop appetitive behavior involved in the reinforcement of eating.

Acetylcholine↗
PubMed2003

Neuropeptide Y: a physiological orexigen modulated by the feedback action of ghrelin and leptin.

Neuropeptide Y (NPY), a 36-amino-acid neuropeptide is the most potent physiological appetite transducer known. Episodic NPY neurosecretion in hypothalamic target sites is temporally linked with onset of the daily feeding pattern. Upregulation of NPY signaling in the arcuate nucleus-paraventricular nucleus (ARC-PVN) neural axis is responsible for the hyperphagia evoked by dieting, fasting, hormonal and genetic factors, and disruption in intrahypothalamic signaling. Clusters of NPY-producing neurons in the ARC that coexpress gamma- amino butyric acid and agouti-related peptide, and those in the brain stem (BS) that coexpress catecholamines and galanin, participate in disparate manners to regulate appetitive behavior. NPY receptors, Y1, Y2, and Y5, expressed by various components of the NPY network, mediate NPY-induced feeding. Imbalance in NPY signaling due either to high or low abundance of NPY at target sites elicits hyperphagia leading to increased fat accretion and obesity. Recent studies show that intermittent, feedback action of opposing afferent hormonal signals-leptin from adipose tissue and ghrelin from stomach-regulate the episodic secretion of orexigenic NPY in the PVN-ARC. Apparently, the hypothalamic NPY network is the primary common pathway intimately involved in genesis of appetite- stimulating impulses.

Animals↗
PubMed2004

Dissociation of core and shell single-unit activity in the nucleus accumbens in free-choice novelty.

Core and shell regions of the nucleus accumbens (NAcc) have been implicated in different aspects of goal-directed behavior. To assess these differences at the neuronal level, we evaluated core and shell single-unit activity in eight rats during one-trial, free-choice entry into a novel compartment. Changes in firing rate during approach of (orientation toward) and entry into (nose cross) novelty were assessed relative to a pre-novelty baseline when the animals were behaviorally active. Increases and decreases in neuronal activity were recorded in both regions during both phases of the novelty response. The regional distribution of these responses, however, was significantly different during the approach phase with roughly equal proportions of neuronal excitations (8/29) and inhibitions (6/29) in core but a shift away from excitation (2/40) toward inhibition (12/40) in shell. No regional differences emerged during subsequent approach of the familiar compartment from the novel chamber or during entry to either the novel or familiar compartment. Taken together, our results during approach to free-choice novelty indicate a regional dissociation in NAcc firing rate may play a role in appetitive behavior.

Action Potentials↗
PubMed2003

Brain-gut axis in pancreatic secretion and appetite control.

The stimulation of exocrine pancreatic secretion that has been attributed by Pavlov exclusively to various reflexes (nervism), was then found that it depend also on numerous enterohormones, especially cholecystokinin (CCK) and secretin, released by duodeno-jejunal mucosa and originally believed to act via an endocrine pathway. Recently, CCK and other enterohormones were found to stimulate the pancreas by excitation of sensory nerves and triggering vago-vagal and entero-pancreatic reflexes. Numerous neurotransmitters and neuropeptides released by enteric nervous system (ENS) of gut and pancreas have been also implicated in the regulation of exocrine pancreas. This article was designed to review the contribution of vagal nerves and entero-hormones, especially CCK and other enterohormones, involved in the control of appetitive behavior such as leptin and ghrelin and pancreatic polypeptide family (peptide YY and neuropeptide Y). Basal secretion shows periodic fluctuations with peals controlled by ENS and by motilin and Ach. Plasma ghrelin, that is considered as hunger hormone, increases under basal conditions, while plasma leptin falls to the lowest level. Postprandial pancreatic secretion, classically divided into cephalic, gastric and intestinal phases, involves predominantly CCK, which under physiological conditions acts almost entirely by activation of vago-vagal reflexes to stimulate the exocrine pancreas, being accompanied by the fall in plasma ghrelin and increase of plasma leptin, reflecting feeding behavior. We conclude that the major role in postprandial pancreatic secretion is played by vagus and gastrin in cephalic and gastric phases and by vagus in conjunction with CCK and secretin in intestinal phase. PP, PYY somatostatin, leptin and ghrelin that affect food intake appear to participate in the feedback control of postprandial pancreatic secretion via hypothalamic centers.

Appetite Regulation↗