The anxiogenic drug yohimbine activates central viscerosensory circuits in rats

Systemic administration of the alpha(2)-adrenoceptor antagonist yohimbine (YO) activates the HPA stress axis and promotes anxiety in humans and experimental animals. We propose that visceral malaise contributes to the stressful and anxiogenic effects of systemic YO and that YO recruits brainstem noradrenergic (NA) and peptidergic neurons that relay viscerosensory signals to the hypothalamus and limbic forebrain. To begin testing these hypotheses, the present study explored dose-related effects of YO on food intake, conditioned flavor avoidance (CFA), and Fos immunolabeling in rats. Systemic YO (5.0 mg/kg BW, i.p.) inhibited food intake, supported CFA, and increased Fos immunolabeling in identified NA neurons in the ventrolateral medulla, nucleus of the solitary tract, and locus coeruleus. YO also increased Fos in the majority of corticotropin releasing hormone-positive neurons in the paraventricular nucleus of the hypothalamus. YO administered at 1.0 mg/kg BW did not inhibit food intake, did not support CFA, and did not increase Fos immunolabeling. Retrograde neural tracing demonstrated that neurons activated by YO at 5.0 mg/kg BW included medullary and pontine neurons that project to the central nucleus of the amygdala and to the lateral bed nucleus of the stria terminalis, the latter region receiving comparatively greater input by Fos-positive neurons. We conclude that YO produces anorexigenic and aversive effects that correlate with activation of brainstem viscerosensory inputs to the limbic forebrain. These findings invite continued investigation of how central viscerosensory signaling pathways interact with hypothalamic and limbic regions to influence interrelated physiological and behavioral components of anxiety, stress, and visceral malaise.     

Microinjection of galanin-like peptide into the medial preoptic area stimulates food intake in adult male rats

Galanin-like peptide (GALP) is a neuropeptide implicated in the regulation of feeding behaviour, metabolism and reproduction. GALP is an endogenous ligand of the galanin receptors, which are widely expressed in the hypothalamus. GALP is predominantly expressed in arcuate nucleus (ARC) neurones, which project to the paraventricular nucleus (PVN) and medial preoptic area (mPOA). Intracerebroventricular or intraparaventricular (iPVN) injection of GALP acutely increases food intake in rats. The effect of GALP injection into the mPOA on feeding behaviour has not previously been studied. In the present study, intra-mPOA (imPOA) injection of GALP potently increased 0-1-h food intake in rats. The dose-response effect of imPOA GALP administration on food intake was similar to that previously observed following iPVN administration. The effects of GALP (1 nmol) or galanin (1 nmol) on food intake were then compared following injection into the PVN, mPOA, ARC, dorsal medial nucleus (DMN), lateral hypothalamus and rostral preoptic area (rPOA). GALP (1 nmol) increased food intake to a similar degree when injected into the imPOA or iPVN, but produced no significant effect when injected into the ARC, DMN, lateral hypothalamus or rPOA. Similarly, galanin (1 nmol) significantly increased food intake following injection imPOA and iPVN. However, the effect was significantly smaller than that following administration of GALP (1 nmol). Galanin also had no significant effect on food intake when administered into the ARC, DMN, lateral hypothalamus and rPOA. These data suggest that the mPOA and the PVN may have specific roles in mediating the orexigenic effect of GALP and galanin.     

Fos expression in the brain induced by peripheral injection of CCK or leptin plus CCK in fasted lean mice

We previously reported a synergistic interaction between leptin and cholecystokinin (CCK) to reduce food intake through CCK-A receptors in lean mice fasted for 24 h. To identify the activated neuronal pathways, we investigated changes in Fos expression in brain nuclei 2 h after single or combined intraperitoneal (i.p.) injections of leptin (120 μg/kg) and sulfated CCK-8 (3.5 μg/kg) in male lean mice (C57BL/6) fasted for 24 h using immunohistochemistry for Fos, the protein product of the early gene, c-fos. Leptin did not increase Fos expression in the brain compared with vehicle-treated mice. CCK increased the numbers of Fos-positive neurons in the nucleus of the solitary tract (NTS)/area postrema (AP), central nucleus of the amygdala (CeA) and, to a smaller extent, in the paraventricular nucleus of the hypothalamus (PVN) (5.2-, 2.3- and 0.3-fold respectively). Injections of leptin–CCK further enhanced Fos expression by 40% in the PVN compared with that induced by CCK alone, but not in the other nuclei. Devazepide (a CCK-A receptor antagonist, 1 mg/kg, i.p.) prevented the increase in Fos expression induced by leptin–CCK in the PVN and by CCK alone in the PVN, CeA and NTS/AP. These results indicate that in fasted mice, i.p. injection of CCK increases Fos expression in specific brain nuclei through CCK-A receptors while leptin alone had no effect. Leptin in conjunction with CCK selectively enhanced Fos expression in the PVN. The PVN may be an important site mediating the synergistic effect of leptin–CCK to regulate food intake.     

Effect of food deprivation and leptin repletion on the plasma levels of estrogen (E2) and NADPH-d reactivity in the ventromedial and arcuate nuclei of the hypothalamus in the female rats

The exact role of leptin in fasting has not been completely elucidated. To determine whether leptin can act in fasting to influence plasma estrogen levels and nitric oxide synthase reactivity in food regulating centers of the brain, we fasted female rats for 4 days and treated them i.p. with vehicle or 100 microg of recombinant mouse leptin as 1 ml on the 3rd and 4th day twice daily (10.00 and 17.00 h). Proestrus blood was collected at 10.00, 14.00, 18.00 and at 22.00 h, plasma obtained and assayed for estrogen (E2) and leptin levels. Verification of ovulation occurrence was by examining the oviduct for extruded ovum. The rat brains were removed and processed for nitric oxide synthase reactivity in the ventromedial hypothalamus (VMH) and arcuate nucleus (ARC) using NADPH-diaphorase histochemistry, a marker for neurons expressing NOS enzyme. Leptin effect on dependable variables such as food intake, water intake and body weight gain was also investigated. Four days fasting significantly decreased body weight, estrogen and postfast leptin levels, nitric oxide reactivity in the VMH and ARC nucleus and stopped ovulation in many (4 out of 5) rats fasted and given vehicle. Leptin treatment significantly increased plasma estrogen and postfast leptin levels, restored ovulation in many (4 out of 5) rats and increased nitric oxide reactivity in the VMH and ARC. Leptin significantly inhibited food intake, water intake and gain in body weight during recommenced feeding. These observations suggest that leptin could act in the pituitary-ovarian axis during fasting to improve reproductive function by partly stimulating estrogen secretion.     

侧脑室注射肾上腺髓质素增加大鼠心血管相关核团中c-Fos的表达

目的 研究侧脑室注射肾上腺髓质素(1nmol／kg，3．nmoL／kg)，对大鼠脑内心血管相关核团中c-fos表达的影响。方法 应用Fos蛋白免疫组化技术。结果 (1)侧脑室注射肾上腺髓质素诱发脑干的孤束核、最后区、蓝斑核、臂旁核和外侧巨细胞旁核，下丘脑的室旁核、视上核和腹内侧核以及前脑的中央杏仁核和外侧缰核等多个部位的心血管中枢出现大量Fos样免疫反应神经元。(2)降钙素基因相关肽受体拮抗剂CGRP8-37(30nmol／kg)可明显减弱肾上腺髓质素(3nmol／kg)的效应。结论 肾上腺髓质素可兴奋脑内多个心血管相关核团的神经元，降钙素基因相关肽受体可能介导这一效应。     

Central administration of aminoprocalcitonin inhibits food intake and stimulates the hypothalamic-pituitary-adrenal axis in rats via the corticotrophin-releasing factor system

Aminoprocalcitonin (N-PCT), a neuroendocrine peptide derived from procalcitonin, reduces food intake and body weight when administered centrally in rats. We have recently shown that N-PCT is expressed in brain areas known to be involved in energy homeostasis, including the paraventricular nucleus (PVN) of the hypothalamus, which contains a prominent population of corticotrophin-releasing factor (CRF)-synthesising neurones. CRF plays a pivotal role in the regulation of the hypothalamic-pituitary adrenal (HPA) axis and food intake. However, little is known about functional interactions of N-PCT and CRF. In the present study, we found endogenous N-PCT protein in the rat PVN. We also showed N-PCT immunoreactivity in PVN co-localised with NeuN, a neuronal marker, or glial fibrillary acidic protein, an astrocyte marker. Double staining immunohistochemistry revealed that N-PCT co-localised with CRF in parvocellular neurones of the PVN. Intracerebroventricular N-PCT administration increased CRF mRNA and content in the hypothalamus, suggesting that N-PCT stimulates the HPA axis and suppresses food intake and body weight via CRF-dependent pathways. In keeping with this, i.c.v. co-injection of D-Phe-CRF(12-41), a CRF receptor antagonist, significantly attenuated N-PCT-induced reduction in food intake and body weight in a dose-dependent manner. Furthermore, i.c.v. administration of N-PCT increased plasma adrenocorticotrophic hormone and corticosterone concentrations and induced the expression of Fos protein, a marker of neuronal activity, in parvocellular CRF neurones. These data collectively support the hypothesis that N-PCT inhibits food intake and body weight and stimulates the HPA axis via CRF-mediated pathways.     

Fos induction in selective hypothalamic neuroendocrine and medullary nuclei by intravenous injection of urocortin and corticotropin-releasing factor in rats

CRF and urocortin, administrated systemically, exert peripheral biological actions which may be mediated by brain pathways. We identified brain neuronal activation induced by intravenous (i.v.) injection of CRF and urocortin in conscious rats by monitoring Fos expression 60 min later. Both peptides (850 pmol/kg, i.v.) increased the number of Fos immunoreactive cells in the paraventricular nucleus of the hypothalamus, supraoptic nucleus, central amygdala, nucleus tractus solitarius and area postrema compared with vehicle injection. Urocortin induced a 4-fold increase in the number of Fos-positive cells in the supraoptic nucleus and a 3.4-fold increase in the lateral magnocellular part of the paraventricular nucleus compared with CRF. Urocortin also elicited Fos expression in the accessory hypothalamic neurosecretory nuclei, ependyma lining the ventricles and choroid plexus which was not observed after CRF. The intensity and pattern of the Fos response were dose-related (85, 255 and 850 pmol/kg, i.v.) and urocortin was more potent than CRF. Neither CRF nor urocortin induced Fos expression in the lateral septal nucleus, Edinger-Westphal nucleus, dorsal raphe nucleus, locus coeruleus, or hypoglossal nucleus. These results show that urocortin, and less potently CRF, injected into the circulation at picomolar doses activate selective brain nuclei involved in the modulation of autonomic/endocrine function; in addition, urocortin induces a distinct activation of hypothalamic neuroendocrine neurons.     

Glucose availability regulates ghrelin‐induced food intake in the ventral tegmental area

Information about metabolic status arrives in the brain in the form of a complex milieu of circulating signalling factors, including glucose and fatty acids, ghrelin, leptin and insulin. The specific interactions between humoural factors, brain sites of action and how they influence behaviour are largely unknown. We have previously observed interactions between glucose availability and the actions of ghrelin mediated via the agouti‐related peptide neurones of the hypothalamus. In the present study, we examine whether these effects generalise to another ghrelin‐sensitive brain nucleus, the ventral tegmental area (VTA). We altered glucose availability by injecting mice with glucose or 2‐deoxyglucose i.p. to induce hyperglycaemia and glucopenia, respectively. Thirty minutes later, we injected ghrelin in the VTA. Glucose administration suppressed intra‐VTA ghrelin‐induced feeding. Leptin, a longer‐term signal of positive energy balance, did not affect intra‐VTA ghrelin‐induced feeding. 2‐Deoxyglucose and ghrelin both increased food intake in their own right and, together, they additively increased feeding. These results add support to the idea that calculation of metabolic need depends on multiple signals across multiple brain regions and identifies that VTA circuits are sensitive to the integration of signals reflecting internal homeostatic state and influencing food intake.     

Divergent Neuronal Circuitries Underlying Acute Orexigenic Effects of Peripheral or Central Ghrelin: Critical Role of Brain Accessibility

Ghrelin is an octanoylated peptide hormone that potently and rapidly increases food intake. The orexigenic action of ghrelin involves the hypothalamic arcuate nucleus (ARC), which is accessible to plasma ghrelin and expresses high levels of the ghrelin receptor. Local administration of ghrelin in a variety of other brain nuclei also increases food intake. It is currently unclear, however, whether these non‐ARC ghrelin brain targets are impacted by physiological increases of plasma ghrelin. Thus, the present study aimed to clarify which ghrelin brain targets participate in the short‐term orexigenic actions of ghrelin. First, c‐Fos induction into mouse brains centrally or peripherally treated with ghrelin was analysed. It was confirmed that peripherally administered ghrelin dose‐dependently increases food intake and mainly activates c‐Fos in ARC neurones. By contrast, centrally administered ghrelin activates c‐Fos in a larger number of brain nuclei. To determine which nuclei are directly accessible to ghrelin, mice were centrally or peripherally injected with a fluorescent ghrelin tracer. It was found that peripherally injected tracer mainly accesses the ARC, whereas centrally injected tracer reaches most brain areas known to express ghrelin receptors. Subsequently, the effects of ghrelin were tested in ARC‐ablated mice and it was found that these mice failed to increase food intake in response to peripherally administered ghrelin but fully responded to centrally administered ghrelin. ARC‐ablated mice showed patterns of ghrelin‐induced c‐Fos expression similar to those seen in control mice with the exception of the ARC, where no c‐Fos was found. Thus, peripheral ghrelin mainly accesses the ARC, which is required for the orexigenic effects of the hormone. Central ghrelin accesses a variety of nuclei, which can mediate the orexigenic effects of the hormone, even in the absence of an intact ARC.     

The distribution of growth-hormone-releasing factor (GRF) immunoreactivity in the central nervous system of the rat: an immunohistochemical study using antisera directed against rat hypothalamic GRF

Immunohistochemical methods have been used to chart the distribution of rat hypothalamic growth-hormone-releasing factor (rhGRF) immunoreactivity in the brains of normal and colchicine-treated adult albino rats. The results suggest the existence of at least two distinct rhGRF-containing systems: one responsible for delivery of the peptide to portal vessels in the median eminence, and one whose relationship, if any, to hypophysiotropic function is less direct. A dense plexus of rhGRF-stained fibers was found throughout the external lamina of the median eminence that is the route by which the peptide is delivered to the anterior pituitary. This projection appears to arise primarily from a group of rhGRF-immunoreactive neurons centered in the arcuate nucleus. Some 1,000-1,500 rhGRF-positive neurons were counted on each side of the brain in rats pretreated with colchicine. Colocalization studies, using a sequential double staining technique, indicated that a subset of rhGRF-immunoreactive neurons in the arcuate region contain neurotensin immunoreactivity. No evidence was obtained for colocalization of rhGRF with either of two pro-opiomelanocortin-derived peptides (alpha-melanocyte-stimulating hormone, adrenocorticotropic hormone (1-24)) in individual neurons in the arcuate nucleus. Much smaller groups of neurons were localized in the parvicellular division of the paraventricular nucleus of the hypothalamus and in the dorsomedial nucleus, and it is unclear whether they contribute to the plexus of rhGRF-stained fibers in the median eminence. The only other region in the rat brain in which rhGRF-stained cells were found reliably was in the area that roughly encapsulates the caudal aspect of the ventromedial nucleus of the hypothalamus. Because cells in this region are not known to project to the median eminence, they may be assumed to contribute to the extrahypophysiotropic rhGRF-stained projections outlined below. From the level of the arcuate and ventromedial nuclei, rhGRF-immunoreactive fibers could be traced along the base of the brain and through the periventricular system to discrete terminal fields limited almost exclusively to the hypothalamus and adjoining parts of the basal telencephalon. All parts of the periventricular region of the hypothalamus receive an input, including the preoptic and anterior parts in which somatostatin-containing neurons that project to the median eminence are clustered. Other prominent terminal fields were localized in discrete parts of the dorsomedial, paraventricular, suprachiasmatic, and premammillary nuclei, and in the medial preoptic and lateral hypothalamic areas.(ABSTRACT TRUNCATED AT 400 WORDS)     

Activation of the rat hypothalamic supramammillary nucleus by food anticipation,food restriction or ghrelin administration

The circulating orexigenic hormone ghrelin targets many brain areas involved in feeding control and signals via a dedicated receptor, the growth hormone secretagogue receptor 1A. One unexplored target area for ghrelin is the supramammillary nucleus (SuM), a hypothalamic area involved in motivation and reinforcement and also recently linked to metabolic control. Given that ghrelin binds to the SuM, we explored whether SuM cells respond to ghrelin and/or are activated when endogenous ghrelin levels are elevated. We found that peripheral ghrelin injection activates SuM cells in rats, reflected by an increase in the number of cells expressing c‐Fos protein in this area, as welll as by the predominantly excitatory response of single SuM cells recorded in in vivo electrophysiological studies. Further c‐Fos mapping studies reveal that this area is also activated in rats in situations when circulating ghrelin levels are known to be elevated: in food‐restricted rats anticipating the consumption of food and in fed rats anticipating the consumption of an energy‐dense food. We also show that intra‐SuM injection of ghrelin induces a feeding response in rats suggesting that, if peripheral ghrelin is able to access the SuM, it may have direct effects on this brain region. Collectively, our data demonstrate that the SuM is activated when peripheral ghrelin levels are high, further supporting the emerging role for this brain area in metabolic and feeding control.     

Centrally administered bombesin activates COX-containing spinally projecting neurons of the PVN in anesthetized rats

The paraventricular nucleus (PVN) of the hypothalamus has a heterogenous structure containing different types of output neurons that project to the median eminence, posterior pituitary, brain stem autonomic centers and sympathetic preganglionic neurons in the spinal cord. Presympathetic neurons in the PVN send mono- and poly-synaptic projections to the spinal cord. In the present study using urethane-anesthetized rats, we examined the effects of centrally administered bombesin (a homologue of the mammalian gastrin-releasing peptide) on the mono-synaptic spinally projecting PVN neurons pre-labeled with a retrograde tracer Fluoro-Gold (FG) injected into T8 level of the spinal cord, with regard to the immunoreactivity for cyclooxygenase (COX) isozymes (COX-1/COX-2) and Fos (a marker of neuronal activation). FG-labeled spinally projecting neurons were abundantly observed in the dorsal cap, ventral part and posterior part of the PVN. The immunoreactivity of each COX-1 and COX-2 was detected in FG-labeled spinally projecting PVN neurons in the vehicle (10 μl of saline/animal, i.c.v.)-treated group, while bombesin (1 nmol/animal, i.c.v.) had no effect on the number of these immunoreactive neurons for each COX isozyme with labeling of FG. On the other hand, the peptide significantly increased the number of double-immunoreactive neurons for Fos and COX-1/COX-2 with FG-labeling in the PVN (except triple-labeled neurons for FG, COX-2 and Fos in the dorsal cap of the PVN), as compared to those of vehicle-treated group. These results suggest that centrally administered bombesin activates spinally projecting PVN neurons containing COX-1 and COX-2 in rats.     

A comparison of the effects of the 5-HT1 agonists TFMPP and RU 24969 on feeding following peripheral or medial hypothalamic injection.

Experiments were conducted to compare the food intake suppressant effects of the 5-hydroxytryptamine (5-HT)₁ agonists 1-3-trifluoro-methylphenylpiperazine hydrochloride (TFMPP) and 5-methoxy-3-(1,2,3,6-tetrahydropyridinyl)1H indole (RU 24969) following either peripheral or medial hypothalamic injections. The effects of these manipulations were examined in 3 different paradigms involving the stimulation of feeding by: (1) infusion of 25 nmol noradrenaline (NA) into the medial hypothalamus, (2) adaptation to a 20 h food deprivation schedule, and (3) the presentation of a palatable wet mash diet for 1 h each day to ad libitum-fed rats. In all 3 paradigms TFMPP and RU 24969 (0.31–5 mg/kg, i.p.) induced dose-dependent reductions of food intake. Both drugs were somewhat less potent at inhibiting feeding that resulted from food deprivation. In contrast to these results medial hypothalamic infusion of TFMPP or RU 24969 (12.5–50 nmol) failed to affect food intake in any of the 3 tests. This occured in spite of the fact that both 5-HT (12.5–50 nmol) and fluoxetine (12.5–50 nmol) mildly attenuated the feeding that resulted from NA infusion into the same site. The results provide clear evidence that the food intake suppressant effects of peripherally injected TFMPP and RU 24969 are not mediated in the medial hypothalamus. They also suggest that even though manipulations of serotonergic function within the medial hypothalamus can alter food intake, this probably does not involve selective activation of 5-HT_1C and/or 5-HT_1B receptors.     

A comparison of the effects of the 5-HT1 agonists TFMPP and RU 24969 on feeding following peripheral or medial hypothalamic injection

Experiments were conducted to compare the food intake suppressant effects of the 5-hydroxytryptamine (5-HT)₁ agonists 1-3-trifluoro-methylphenylpiperazine hydrochloride (TFMPP) and 5-methoxy-3-(1,2,3,6-tetrahydropyridinyl)1H indole (RU 24969) following either peripheral or medial hypothalamic injections. The effects of these manipulations were examined in 3 different paradigms involving the stimulation of feeding by: (1) infusion of 25 nmol noradrenaline (NA) into the medial hypothalamus, (2) adaptation to a 20 h food deprivation schedule, and (3) the presentation of a palatable wet mash diet for 1 h each day to ad libitum-fed rats. In all 3 paradigms TFMPP and RU 24969 (0.31–5 mg/kg, i.p.) induced dose-dependent reductions of food intake. Both drugs were somewhat less potent at inhibiting feeding that resulted from food deprivation. In contrast to these results medial hypothalamic infusion of TFMPP or RU 24969 (12.5–50 nmol) failed to affect food intake in any of the 3 tests. This occured in spite of the fact that both 5-HT (12.5–50 nmol) and fluoxetine (12.5–50 nmol) mildly attenuated the feeding that resulted from NA infusion into the same site. The results provide clear evidence that the food intake suppressant effects of peripherally injected TFMPP and RU 24969 are not mediated in the medial hypothalamus. They also suggest that even though manipulations of serotonergic function within the medial hypothalamus can alter food intake, this probably does not involve selective activation of 5-HT_1C and/or 5-HT_1B receptors.     

Galanin Antagonists Block Galanin-induced Feeding in the Hypothalamus and Amygdala of the Rat

Galanin significantly increased food intake when microinjected into the region of the central nucleus of the amygdala as well as into the paraventricular nucleus of the hypothalamus. In the amygdala this effect was specific to feeding; no change in grooming, resting, or other behaviour was observed after galanin treatment. These results provide evidence that the amygdala may be an important site in the mediation of galanin-induced feeding. The galanin receptor antagonists, C7 and M40, antagonized galanin-induced feeding, while having no effect alone on food consumption in free-feeding rats. These new galanin receptor antagonists provide useful tools for further investigating the role of endogenous galanin in the regulation of feeding.     

The role of the vagus nerve in mediating the long-term anorectic effects of leptin

Leptin, the product of the obese (ob) gene, is mainly known for its regulatory role of energy balance by direct activation of hypothalamic receptors. Recently, its function in the acute control of food intake was additionally attributed to activation of the vagus nerve to regulate meal termination. Whether vagal afferent neurones are involved in longer term effects of leptin on food intake, however, remains undetermined. Using vagotomised (VGX) rats, we sought to clarify the contributions of vagal afferents in mediating the long-lasting effect of leptin on appetite suppression. Intraperitoneal (i.p.) injection of leptin (3.5 mg/kg) attenuated food intake at 4, 6, 8 and 24 h and body weight at 24 h postinjection in SHAM-operated rats; however, this response was not abrogated by vagotomy. In a separate study using immunohistochemistry, we observed leptin-induced Fos expression in the nucleus tractus solitarii, a brain structure where vagal afferent fibres terminate. This signal was not attenuated in VGX animals compared to the SHAM group. Moreover, leptin treatment led to a similar level of nuclear STAT3 translocation, a marker of leptin signalling, in the hypothalami of SHAM and VGX animals. In addition to the effects of leptin, vagotomy surgery itself resulted in a decrease of 24 h food intake. Analyses of brains from saline-treated VGX animals revealed a significant induction of Fos in the nucleus tractus solitarii and changes in agouti-related peptide and pro-opiomelanocortin mRNA expression in the hypothalamus compared to their SHAM counterparts, indicating that the vagotomy surgery itself induced a modification of brain activity in areas involved in regulating appetite. Collectively, our data suggest that vagal afferents do not constitute a major route of mediating the regulatory effect of leptin on food intake over a period of several hours.     

Short-term anorexigenic effects of central neuropeptide VF are associated with hypothalamic changes in chicks

The present study was designed to measure food and water intake, changes in hypothalamic chemistry, and other behaviour modifications after central injection of neuropeptide (NP) VF in broiler type chicks. In Experiment 1, chicks responded to central NPVF with a reduction in food intake for up to 90 min post injection. Water intake was unaffected. In Experiment 2, NPVF exerted a less potent and shorter duration of attenuated food intake than did the structurally related NPFF. In Experiment 3, 16.0 nmol NPVF reversed the prolactin-releasing peptide induced orexigenic effect. In Experiment 4, central NPVF treatment was associated with decreased c-Fos immunoreactivity in the lateral hypothalamus, whereas c-Fos immunoreactivity in the dorsomedial nucleus, infundibular nucleus (homologue to the mammalian arcuate nucleus) and ventromedial nucleus was increased. In Experiment 5, behaviours unrelated to ingestion including sit, stand, deep rest and locomotion were affected by central NPVF injection. Some of these behaviours are incompatible with ingestion and may contribute to hypothalamic associated perception of satiety after central NPVF. In conclusion, NVPF is a short-term regulator of appetite and its effects are associated with hypothalamic and behaviour changes in chicks.