Centrally and peripherally administered bombesin decreases food intake in turkeys

Neuropeptide Control of Feeding Behavior in Birds and Its Difference with Mammals

Feeding is an essential behavior for animals to sustain their lives. Over the past several decades, many neuropeptides that regulate feeding behavior have been identified in vertebrates. These neuropeptides are called “feeding regulatory neuropeptides.” There have been numerous studies on the role of feeding regulatory neuropeptides in vertebrates including birds. Some feeding regulatory neuropeptides show different effects on feeding behavior between birds and other vertebrates, particularly mammals. The difference is marked with orexigenic neuropeptides. For example, melanin-concentrating hormone, orexin, and motilin, which are regarded as orexigenic neuropeptides in mammals, have no effect on feeding behavior in birds. Furthermore, ghrelin and growth hormone-releasing hormone, which are also known as orexigenic neuropeptides in mammals, suppress feeding behavior in birds. Thus, it is likely that the feeding regulatory mechanism has changed during the evolution of vertebrates. This review summarizes the recent knowledge of peptidergic feeding regulatory factors in birds and discusses the difference in their action between birds and other vertebrates.

Peripheral injection of bombesin induces c-Fos in NUCB2/nesfatin-1 neurons

As anorexigenic hormones bombesin and nucleobindin2 (NUCB2)/nesfatin-1 decrease food intake in rodents. Both hormones have been described in brain nuclei that play a role in the modulation of hunger and satiety, like the paraventricular nucleus of the hypothalamus (PVN) and the nucleus of the solitary tract (NTS). However, the direct interaction of the two hormones is unknown so far. The aim of study was to elucidate whether bombesin directly interacts with NUCB2/nesfatin-1 neurons in the PVN and NTS. Therefore, we injected bombesin intraperitoneally (ip) at two doses (26 and 32nmol/kg body weight) and assessed c-Fos activation in the PVN, arcuate nucleus (ARC) and NTS compared to vehicle treated rats (0.15M NaCl). We also performed co-localization studies with oxytocin or tyrosine hydroxylase. Bombesin at both doses increased the number of c-Fos positive neurons in the PVN (p<0.05) and NTS (p<0.05) compared to vehicle, while in the ARC no modulation was observed (p>0.05). In the PVN and NTS the number of c-Fos positive neurons colocalized with NUCB2/nesfatin-1 increased after bombesin injection compared to vehicle treatment (p<0.05). Moreover, an increase of activated NUCB2/nesfatin-1 immunoreactive neurons that co-expressed oxytocin in the PVN (p<0.05) or tyrosine hydroxylase in the NTS (p<0.05) was observed compared to vehicle. Our results show that peripherally injected bombesin activates NUCB2/nesfatin-1 neurons in the PVN and NTS giving rise to a possible interaction between bombesin and NUCB2/nesfatin-1 in the modulation of food intake.

Gastrin releasing peptide-29 evokes feeding responses in the rat

In mammals, gastrin releasing peptide (GRP) 10 and 27 reduce food intake. In the current work, we test the hypothesis that GRP-29, the large molecular form of GRP in the rat, also evokes feeding responses consistent with a possible role in satiety. Here, we measured three feeding responses, size of first meal, intermeal interval (IMI, time between first and second meal) and satiety ratio (SR, satiation period for every unit of food consumed in the first meal), in overnight food deprived rats following GRP-10, 27 or 29 (0, 0.3, 1.0, 2.1, 4.1, 10.3, 17.2nmol/kg) intraperitoneally and presentation of a 10% sucrose test diet. GRP-29 and GRP-27 reduced the size of the first meal, prolonged IMI and increased SR, but GRP-10 failed to exhibit similar feeding responses. The order of potency was GRP-29=GRP-27>GRP-10. The current data support a role for GRP-29 in the short-term regulation of food intake.

Differential thresholds of neuromedins B-, C-, and bombesin-induced anorexia and crop-emptying rate in chicks

Neuromedin B (NMB) and neuromedin C (NMC) are homologs of bombesin and are distributed throughout both the brain and gastrointestinal tract. The physiological roles of these bombesin-like peptides in chicks (Gallus gallus) have not been documented. Therefore, the purpose of the present study was to measure the effects of these bombesin-like peptides on food intake, crop-emptying rate and body temperature in chicks, and then to compare these effects with those of bombesin. Intracerebroventricular (ICV, 5 nmol) and intraperitoneal (IP, 300 nmol/kg) injections of NMB, NMC, and bombesin significantly decreased food deprivation-induced food intake. When ICV injected (5 nmol), all three peptides significantly reduced crop-emptying rate. IP injection of NMC and bombesin (300 nmol/kg) also reduced crop-emptying rate while NMB did not. The magnitude of food intake suppression and crop-emptying rate reduction were greater for bombesin than NMB and NMC. ICV and IP injections of NMB, NMC and bombesin did not affect cloacal temperature. In sum, the present study suggests that central and peripheral NMB and NMC are associated with reduced food intake and crop-emptying of chicks, but these effects are weaker than those of bombesin.

Central litorin injection is associated with primary anorexigenic effects that coincide with activation of the magnocellular division of the paraventricular nucleus

The central mechanism that mediates litorin-induced satiety is poorly understood, and has not been studied in a non-mammalian species. Therefore, the aim of this study was to determine if litorin-induced satiety in an alternative vertebrate model, the chick, and to elucidate some of the central mechanisms that are associated with this response. In Experiment 1, chicks responded to intracerebroventricular (ICV) injection of litorin with reduced food intake at all doses tested (0.1, 1.0, and 10 nmol), while concurrently, an anti-dipsogenic effect was observed in the two higher doses tested. Whole blood glucose concentrations were not affected. In Experiment 2, chicks that were food-withheld did not reduce their water intake after ICV litorin injection. To determine if litorin affected behaviors unrelated to ingestion, a comprehensive behavior analysis was conducted as Experiment 3. Of the behaviors observed, only the number of feeding pecks was reduced. Other behaviors such as movement, defecation, escape, posture, or deep rest were not affected. Lastly, in Experiment 4, litorin-treated chicks had an increased number of c-Fos immunoreactive cells in the magnocellular division of the paraventricular nucleus. The arcuate nucleus, dorsomedial nucleus, lateral hypothalamus, parvicellular division of the paraventricular nucleus, suprachiasmatic nucleus, periventricular nucleus and the ventromedial hypothalamus were not affected. Therefore, we conclude that ICV litorin causes anorexigenic effects in chicks associated with changes in hypothalamic chemistry that appear to be behavior specific.

Central and peripheral alytesin cause short-term anorexigenic effects in neonatal chicks

We studied the effects of alytesin, a natural analogue of bombesin, on appetite-related responses and behaviors in neonatal chicks. Chicks responded to both intracerebroventricular (ICV) and peripheral injections of alytesin with short-term reduced feed intake. ICV alytesin caused reduced short-term water intake when feed was present, but we determined this effect was secondary to feed intake since an effect on water intake was not detected in feed-restricted alytesin-treated chicks. The anorexigenic effect of both ICV and peripheral alytesin may be mediated at the hypothalamus, since all hypothalamic nuclei studied; regio lateralis hypothalami, nucleus dorsomedialis hypothalami, nucleus paraventricularis magnocellularis, nucleus perventricularis hypothalami, nucleus infundibuli hypothalami and the nucleus ventromedialis hypothalami, were activated as evident by increased c-Fos immunoreactivity. Central alytesin did not cause increased behaviors that were unrelated to ingestion and did not cause anxiety-related behavior patterns. Additionally, central alytesin did not affect pecking efficacy. We conclude that both ICV and peripheral alytesin injections induce anorexigenic effects in chicks, and the hypothalamus is involved. While the anorexigenic effects of alytesin and bombesin appear to be conserved across species, the two peptides may differ in other behavioral responses and central mechanisms of action.

Bombesin-like peptides and associated receptors within the brain: distribution and behavioral implications

As we commemorate the 25th anniversary of the journal Peptides, it is timely to review the functional significance of the bombesin (BB)-like peptides and receptors in the CNS. Over two decades ago we published an article in the journal Peptides demonstrating that BB-like peptides are present in high densities in certain rat brain regions (such as the paraventricular nucleus of the hypothalamus). Subsequently, one of the mammalian forms of BB, gastrin-releasing peptide (GRP) containing cell bodies were found in the suprachiasmatic nucleus of the hypothalamus and nucleus of the solitary tract of the hindbrain. Another related peptide, namely neuromedin (NM)B, was detected in the olfactory bulb and dentate gyrus. BB and GRP bind with high affinity to BB(2) receptors, whereas NMB binds with high affinity to BB(1) receptors. The actions of BB or GRP are blocked by BB(2) receptor antagonists such as (Psi(13,14)-Leu(14))BB whereas PD168368 is a BB(1) receptor antagonist. Exogenous administration of BB into the rat brain causes hypothermia, hyperglycemia, grooming and satiety. BB-like peptides activate the sympathetic nervous system and appear to modulate stress, fear and anxiety responses. GRP and NMB modulate distinct biological processes through discrete brain regions or circuits, and globally these peptidergic systems may serve in an integrative or homeostatic function.

Distributions of two chicken bombesin receptors, bombesin receptor subtype-3.5 (chBRS-3.5) and gastrin-releasing peptide receptor (chGRP-R) mRNAS in the chicken telencephalon

Bombesin (BN)-like peptide receptors are known to be essential to the regulation of not only homeostasis, including feeding behavior, but also of emotional systems in mammal. Recently, two novel BN receptors, chicken BN-like peptide receptor subtype-3.5 (chBRS-3.5) and gastrin-releasing peptide receptor (chGRP-R), have been identified. Here, we report the localizations of these receptors' mRNAs in the chick brain through development using in situ hybridization. First, chBRS-3.5 mRNA signals were found in the dorsal ventricular ridge at embryonic day (ED) 9. Strong signals were observed in the hyperpallium accessorium, nidopallium and nucleus basorostralis pallii, and moderate signals were found in the hippocampus, cortex piriformis, hyperpallium intercalatum, area temporo-parieto-occipitalis, nucleus striae terminalis lateralis, nucleus olfactorius anterior and organum septi lateralis at ED16. This wide expression in the pallium persisted during posthatch periods. Abundant expressions in the hyperpallium, nidopallium, considered to be similar to the mammalian cortex, as well as in the hippocampus, indicate participation of these molecules in the processing of sensory information, motor function, learning and memory. Telencephalic areas devoid of chBRS-3.5 signals were the entopallium, arcopallium anterius, globus pallidus, nucleus intrapeduncularis, tuberculum olfactorius, nucleus septalis lateralis, hypothalamic and thalamic areas. In contrast to chBRS-3.5, chGRP-R mRNA signals were found in the pallidum at ED5 and 9. At ED16, chGRP-R mRNA signals were localized in the medial striatum and hypothalamus. GRP-R expression in the hypothalamic region was phylogenically conserved. Thus, chBRS-3.5 mRNA signals were distributed in a broader region and were more intense than chGRP-R mRNA. Taken together, chGRP-R and chBRS-3.5 mRNA occurred in similar regions of mammals that express GRP-R. BN/GRP-immunoreactive neurons and varicosities were found mainly in the pallium, especially in the hyperpallium accessorium and nidopallium, and this distribution coincided with that of chBRS-3.5 mRNA. This result suggests that the endogenous ligands for chBRS-3.5 were likely BN-like peptides produced in the pallium.

Molecular cloning and characterization of avian bombesin-like peptide receptors: new tools for investigating molecular basis for ligand selectivity

(1) Bombesin (BN), originally isolated from amphibians, is structurally related to a family of BN-like peptides found in mammals, which include gastrin-releasing peptide (GRP) and neuromedin B (NMB). These peptides have important effects on secretion, smooth muscle contraction, metabolism and behavior. Here we report cloning and characterization of two subtypes of BN-like peptide receptors in Aves. (2) The amino-acid sequence of chick GRP-R (chGRP-R) is highly identical with mammalian and amphibian GRP-R, and this receptor showed high affinity for GRP, BN and synthetic bombesin agonist, [D-Phe(6), beta-Ala(11), Phe(13), Nle(14)]bombesin(6-14) ([FAFNl]BN(6-14)). The chGRP-R gene was localized to chicken chromosome 1q23distal-q24proximal, where chick homologs of other human X-linked genes have also been mapped. (3) ChBRS-3.5, having sequence similarities to both mammalian bombesin-like peptide receptor subtype-3 and amphibian bombesin-like peptide receptor subtype-4, showed high affinity for [FAFNl]BN(6-14), moderate affinity for BN, but low affinity for both GRP and NMB. (4) Expression of both receptors was detected in brain, but only chGRP-R was expressed in gastrointestinal (GI) tissues. (5) When expressed in Chinese hamster ovary K1 cells, these receptors mediate intracellular calcium mobilization upon agonist stimulation. These results suggest that a novel BN peptide may occur in Aves as an endogenous ligand for chBRS-3.5. (6) The receptor sequences responsible for ligand selectivities were discussed and this knowledge about avian BN-like peptide receptors will help us to understand the molecular basis for agonist sensitivities of BN-like peptide receptors.

The interaction of bombesin and corticotropin-releasing hormone on ingestive behavior in the domestic fowl

An experiment was conducted to investigate if bombesin (BM) elicits its effects on feeding through the release of corticotropin-releasing factor (CRF). Single Comb White Leghorn (SCWL) and broiler cockerels were stereotaxically implanted with a 23-gauge stainless steel cannula in the right lateral ventricle. Birds were infused with 0 or 0.5 microg BM, 5 microg alphaCRF (a CRF antagonist), or a combination of both. Food and water consumption were monitored at 15-min intervals through 3 h postinjection. Food and water consumption were both significantly decreased by BM in both SCWL and broilers. In SCWL, alphaCRF had no effect on food intake by itself, but attenuated the effects of BM. In broilers, alphaCRF caused a slight, but significant, decrease in food intake, but also attenuated the effects of BM. Water consumption was not affected by alphaCRF in either broilers or SCWL. We conclude that BM may mediate its central effects on food intake in chickens through the release of CRF.

Neuropeptides, food intake and body weight regulation: a hypothalamic focus

Energy homeostasis is controlled by a complex neuroendocrine system consisting of peripheral signals like leptin and central signals, in particular, neuropeptides. Several neuropeptides with anorexigenic (POMC, CART, and CRH) as well as orexigenic (NPY, AgRP, and MCH) actions are involved in this complex (partly redundant) controlling system. Starvation as well as overfeeding lead to changes in expression levels of these neuropeptides, which act downstream of leptin, resulting in a physiological response. In this review the role of several anorexigenic and orexigenic (hypothalamic) neuropeptides on food intake and body weight regulation is summarized.

Effects of peptides on animal and human behavior: a review of studies published in the first twenty years of the journal Peptides

This review catalogs effects of peptides on various aspects of animal and human behavior as published in the journal Peptides in its first twenty years. Topics covered include: activity levels, addiction behavior, ingestive behaviors, learning and memory-based behaviors, nociceptive behaviors, social and sexual behavior, and stereotyped and other behaviors. There are separate tables for these behaviors and a short introduction for each section.

Regulatory peptides and control of food intake in non-mammalian vertebrates

The current view of the control of food intake involves a central feeding system in the hypothalamus receiving input from peripheral systems. The presence of food in the gut stimulates the release of several regulatory peptides that control gut motility and secretion. Some of these peptides also act as feedback satiety signals, responsible for termination of a meal. Among the regulatory peptides suggested as peripheral satiety signals are cholecystokinin and gastrin releasing peptide. A more long-term peripheral regulation of food intake has also been postulated and leptin has been suggested as a regulator of food intake. Several regulatory peptides mediate orexigenic or anorexigenic effects in the central feeding system. Neuropeptide Y and galanin both act centrally and stimulate the intake of food, while corticotropin releasing factor reduces food intake. At present, most information about the regulation of food intake is gained from mammalian studies and these findings are used as a base for a discussion on the current knowledge of how regulatory peptides control appetite in non-mammalian vertebrates.

Bombesin-like peptides: studies on food intake and social behaviour with receptor knock-out mice

Bombesin (BN)-like peptides and receptors for these peptides are widely distributed in mammalian peripheral tissues and the central nervous system. The physiological and behavioural functions of these peptides have been clarified by both in vivo and in vitro studies. In spite of intensive investigations, the functions of endogenous BN-like peptides remain unclear. In order to specify these functions, our group and another laboratory generated by gene targeting mutant mice that lack one of the three BN-like peptide receptors found in mammals, ie neuromedin B receptor (NMB-R; BB1), gastrin-releasing peptide receptor (GRP-R; BB2), or bombesin receptor subtype-3 (BRS-3; BB3). Using these mutant mouse, we have found unexpected phenotypes, such as hyperphagia and obesity in the BRS-3-deficient mouse, and abnormal social behaviour in the GRP-R-deficient mouse. In the present study, we present our most recent findings in addition to previous studies and discuss the functions of BN-like peptides related to feeding and social behaviour from the point of view of knock-out mice studies.

Central bombesin inhibits food intake and the orexigenic effect of neuropeptide Y in the neonatal chick

It is well known that central injection of bombesin (BN) suppresses feeding in mammalian and avian species, but the anorexigenic effect of central BN are still open with special reference to the chick. The dose response (0, 0.1 and 0.5 microg) of intracerebroventricular (ICV) injection of BN was examined in Experiment 1. ICV injection of BN inhibited food intake in a dose-dependent manner. Experiment 2 was done to determine whether BN interacts with the orexigenic effect of neuropeptide Y (NPY) in the neonatal chick. Central administration of NPY (2.5 microg) greatly enhanced food intake, but co-injection of BN (0.5 microg) suppressed food intake. The dose response of NPY (2.5 microg) co-injected with three levels of BN (0, 0.1 and 0.5 microg) was examined in Experiment 3. ICV injection of BN attenuated the hyperphagia by NPY in a dose-related fashion. It is suggested that central BN may interact with NPY for the regulation of feeding in the neonatal chick.

Bombesin microinjection into the basolateral amygdala influences feeding behavior in the rat

It has been demonstrated that the basolateral amygdala (ABL) represents a satiety mechanism. Experimental data indicate that peripheral or central applications of neuropeptide bombesin (BN) and BN-like peptides inhibit feeding. Since the amygdala (AMY) is rich in BN-like immunoreactive elements, the present study was performed to determine whether 10 or 40 ng doses of BN microinjected bilaterally into the ABL could modify solid food intake. Twenty nanograms of BN (10 ng per injection site) in 24-h deprived rats caused transient inhibition of food intake and 80 ng resulted in a significant reduction of food consumption for 1 h. This inhibitory effect of BN on feeding was eliminated by prior BN antagonist treatment. Results of behavioral tests showed that BN microinjections into the ABL specifically reduced food intake without altering behavioral patterns or influencing the body temperature. Present results suggest that BN-like peptides may act as a complex satiety signal in the ABL.

Role of bombesin-related peptides in the control of food intake

In 1970, Erspamer et al.(1,14)isolated and characterized the tetradecapeptide bombesin (BN) from the skin of amphibian frog Bombina bombina. Subsequently, several BN-like peptides have been identified in mammals, consisting of various forms of gastrin-releasing peptide (GRP) and/or neuromedin B (NMB), together with their distinct receptor subtypes. It has been proposed that BN-related peptides may be released from the gastrointestinal (GI)-tract in response to ingested food, and that they bridge the gut and brain (through neurocrine means) to inhibit further food intake. Conversely, the suppression of release of BN-like peptides at relevant brain nuclei may signal the initiation of a feeding episode. The present review will describe recent pharmacological, molecular, behavioral and physiological experiments, supporting the contention that endogenous BN-related peptides do indeed influence ingestive behaviors. Particular attention is focused on the relationship between these peptides in the peripheral compartment and their impact on central circuits using GRP and/or NMB as transmitters. In addition, however, we will point out various caveats and conundrums that preclude unequivocal conclusions about the precise role(s) of these peptides and their mechanism(s) of action. We conclude that BN-related peptides play an important role in the control of food intake, and may contribute to ingestive disruptions associated with anorexia (anorexia nervosa, AIDS and cancer anorexia), bulimia, obesity and depression. Hence, pharmacological targeting of these systems may be of therapeutic value.

Bombesin injection into the central amygdala influences feeding behavior in the rat

The present study was performed to determine whether low doses (10 or 40 ng) of bombesin microinjected into the amygdala could modify solid food intake. Forty ng of bombesin in 24 h deprived rats caused transient inhibition of food intake. This inhibitory effect was eliminated by prior bombesin antagonist treatment. A series of quantitative behavioral tests indicated that low doses of bombesin application specifically reduced food intake without altering the behavioral pattern or influencing the body temperature. The present results suggest, that bombesin-like peptides may act as a satiety signal in the central part of the amygdala.

Brief, meal-contingent infusions of gastrin-releasing peptide1-27 and neuromedin B-10 inhibit spontaneous feeding in rats

We have previously shown that brief, meal-contingent infusions of the amphibian peptide bombesin (BN) reduce meal size in spontaneously feeding rats. These inhibitory effects presumably reflect actions of BN on receptors for its mammalian homologues, which include gastrin-releasing peptide1-27 (GRP) and neuromedin B-10 (NMB). In the present study, we used the spontaneous feeding paradigm to explore the effects of meal-contingent infusions of these mammalian homologues. Undisturbed, ad lib-fed male rats (n = 12) with chronic inferior vena caval catheters were infused with saline, 5 nmol/kg GRP, 5 nmol/kg NMB, and a mixture of 5 nmol/kg GRP and 5 nmol/kg NMB in counterbalanced order, with intervening noninfusion days. Infusions were remotely activated at the onset of the first nocturnal meal and continued for 3 min (34 microliters/min), delivery being completed within the first 2 min of infusion. Feeding was measured via electronic balances linked to a computer. The effects of all peptide conditions were confined to the first nocturnal meal. Significant and comparable decreases in the size and duration of this meal were observed with GRP, NMB, and GRP + NMB, with no significant effects on the intermeal interval or satiety ratio (intermeal interval/meal size). Thus, brief vena caval infusions of GRP and NMB, given alone or together at the onset of the first nocturnal meal, significantly reduced meal size and duration in spontaneously feeding rats.

Vena caval bombesin infusion decreases spontaneous meal size in undisturbed rats

The amphibian tetradecapeptide bombesin (BN) decreases food intake in both humans and animals. Studies have typically examined the effects of BN on scheduled meals in deprived subjects. To investigate the properties of this peptide under more naturalistic conditions, we examined the effects of BN in spontaneously feeding rats. Undisturbed, ad lib-fed male rats (n = 9) with chronic inferior vena caval catheters were infused with saline vehicle and each of 3 doses (2, 4, and 8 micrograms/kg) of BN in counterbalanced order with intervening noninfusion days. Infusions were remotely activated at the onset of the first nocturnal meal and continued for 3 min (34 microliters/min), delivery being completed within the first 2 min of infusion. Feeding was measured via electronic balances linked to a computer. All doses of the peptide significantly decreased the size and duration of the first nocturnal meal. In addition, 4 and 8 micrograms/kg of BN significantly shortened the intermeal interval from the end of the first meal to the beginning of the second meal. Despite this, the satiety ratio (interval/meal size) tended to increase after BN and was significantly increased by the highest dose (8 micrograms/kg), thus indicating a sustained satiety action of the peptide. In summary, these results show that brief, meal-contingent intravenous infusions of BN potently inhibit spontaneous feeding in undisturbed rats.

Simultaneous administration of neuromedin B-10 and gastrin-releasing peptide(1-27) reproduces the satiating and microstructural effects of bombesin

Bombesin (BN) suppresses food intake more than an equimolar dose of neuromedin B-10 (NMB-10) or gastrin-releasing peptide(1-27) [GRP(1-27)]. Because BN is active at both NMB- and GRP-preferring receptors, it is possible that its greater potency is due to the simultaneous activation of both receptor subtypes. This hypothesis was tested by administering a mixture of NMB-10 and GRP(1-27). The results were consistent with our hypothesis: administration of the mixture of NMB-10 and GRP(1-27) produced an inhibition of intake volume and total licks equivalent to that seen after an equimolar dose of BN and resulted in similar changes in the rate and pattern of licking.

Microstructural analysis of licking behavior following peripheral administration of bombesin or gastrin-releasing peptide

To determine the effects of bombesin (BN) and gastrin-releasing peptide [GRP(1-27)] on food intake and the microstructure of licking, the rate and pattern of licking were measured by lickometer after intraperitoneal administration of 2, 4, 8, and 16 micrograms/kg of each peptide. Although both peptides inhibited intake significantly, the dose-response functions of the peptides were different. At lower doses (2-4 micrograms/kg) the peptides were equipotent; at higher doses (8-16 micrograms/kg) BN was significantly more potent than GRP(1-27), possibly due to an action of BN on neuromedin B (NMB) receptors. The microstructural results demonstrated that both peptides decreased intake by increasing the rate of decay of licking and decreasing the number of bursts and clusters without changing the initial rate of licking or the size of the bursts and clusters. This combination of microstructural changes is evidence that both peptides increased the postingestive negative feedback effects of the diet without changing the orosensory positive feedback. These results are consistent with, but do not prove, the hypothesis that endogenous GRP(1-27) acts as a postingestive satiety signal in rats.

Role of neuropeptides in the regulation of feeding behavior: a review of cholecystokinin, bombesin, neuropeptide Y, and galanin

The purpose of this report is to provide a review of four peptides (cholecystokinin, bombesin, neuropeptide Y, galanin) and their role in feeding behavior. Cholecystokinin (CCK) and bombesin (BBS) are considered satiety peptides, and neuropeptide Y (NPY) and galanin (GAL) have been proposed as appetite peptides. For the purposes of this review, satiety refers to the physiological cessation of feeding, and appetite refers to the drive to eat and exists in gradations.

Desmethionine-bombesin receptor antagonist blocks bombesin-induced inhibition of alcohol intake

[D-Phe6,Des-Met14]bombesin(6-14), ethyl amide (D-BN) is a specific, competitive receptor antagonist of bombesin, a neuropeptide that inhibits alcohol and food intake. We tested the effects of IP injected D-BN (4-400 micrograms/kg) on bombesin-induced (4 micrograms/kg) reduction of caloric intake. In the first experiment, ad lib-fed female and male rats (Ns = 18) were deprived of water for 23 h, injected with peptides or saline in randomized sequences of doses, and immediately given access to 5% w/v ethanol for 30 min, followed by 30 min of water. In a second experiment, male rats (N = 10) were injected with the antagonist at 10 or 20 min prior to bombesin injection and alcohol access, and behaviors were observed and quantified once a minute with an instantaneous time-sampling technique. D-BN injection blocked the bombesin-induced reduction in alcohol intake (> or = 40 micrograms/kg) and food intake (> or = 200 micrograms/kg). When injected 20 min prior to access, D-BN alone (200 micrograms/kg) initially elevated alcohol drinking and later increased feeding behaviors and decreased resting, relative to saline injection. Results indicate bombesin-induced reduction of alcohol intake depends on a specific peptidergic receptor process, and endogenous bombesin-like peptide could act physiologically to elicit satiation with ethanol and food.

CNS effects of peptides: a cross-listing of peptides and their central actions published in the journal Peptides, 1986-1993

The centrally mediated effects of peptides as published in the journal Peptides from 1986 to 1993 are tabulated in two ways. In one table, the peptides are listed alphabetically. In another table, the effects are arranged alphabetically. Most of the effects observed after administration of peptides are grouped, wherever possible, into categories such as cardiovascular and gastrointestinal. The species used in most cases has been rats; where other animals were used, the species is noted. The route of administration of peptides and source of information also are included in the tables, with a complete listing provided at the end. Many peptides have been shown to exert a large number of centrally mediated effects.