P2X(7) receptor activation amplifies lipopolysaccharide-induced vascular hyporeactivity via interleukin-1 beta release

Lipopolysaccharide (LPS) stimulates cytoplasmic accumulation of pro-interleukin (IL)-1 beta. Activation of P2X(7) receptors stimulates conversion of pro-IL-1 beta into mature IL-1 beta, which is then secreted. Because both LPS (in vivo) and IL-1 beta (in vitro) decrease vascular reactivity to contractile agents, we hypothesized the following: 1) P2X(7) receptor activation contributes to LPS-induced vascular hyporeactivity, and 2) IL-1 beta mediates this change. Thoracic aortas were obtained from 12-week-old male C57BL/6 mice. The aortic rings were incubated for 24 h in Dulbecco`s modified Eagle`s medium, LPS, benzoylbenzoyl-ATP (BzATP; P2X(7) receptor agonist), LPS plus BzATP, oxidized ATP (oATP; P2X(7) receptor antagonist), or oATP plus LPS plus BzATP. After the treatment, the rings were either mounted in a myograph for evaluation of contractile activity or homogenized for IL-1 beta and inducible nitric-oxide synthase (iNOS) protein measurement. In endothelium-intact aortic rings, phenylephrine (PE)-induced contractions were not altered by incubation with LPS or BzATP, but they significantly decreased in aortic rings incubated with LPS plus BzATP. Treatment with oATP or IL-1ra (IL-1 beta receptor antagonist) reversed LPS plus BzATP-induced hyporeactivity to PE. In the presence of N(G)-nitro-L-arginine methyl ester or N-([3-(aminomethyl) phenyl] methyl) ethanimidamide (selective iNOS inhibitor), the vascular hyporeactivity induced by LPS plus BzATP on PE responses was not observed. BzATP augmented LPS-induced IL-1 beta release and iNOS protein expression, and these effects were also inhibited by oATP. Moreover, incubation of endothelium-intact aortic rings with IL-1 beta induced iNOS protein expression. Thus, activation of P2X 7 receptor amplifies LPS-induced hyporeactivity in mouse endothelium-intact aorta, which is associated with IL-1 beta-mediated release of nitric oxide by iNOS.

Anxiolytic-like effects induced by acute reversible inactivation of the bed nucleus of stria terminalis

There is conflicting evidence concerning the role of the bed nucleus of the stria terminalis (BNST) in fear and anxiety-elicited behavior. Most of the studies investigating this role, however, employed irreversible lesions of this nucleus. The objective of the present study was to investigate the effects of an acute and reversible inactivation of the BNST in rats submitted to the Vogel conflict test (VCT) and contextual fear conditioning, two widely employed animal models that are responsive to prototypal anxiolytic drugs. Male Wistar rats were submitted to stereotaxic surgery to bilaterally implant cannulae into the BNST. Ten minutes before the test they received bilateral microinjections of cobalt chloride (COCl(2)) (1 mM/100 nL), a nonselective synapse blocker. COCl(2) produced anxiolytic-like effects in tests, increasing the number of punished licks in the VCT and decreasing freezing behavior and the increase in mean arterial blood pressure and heart rate of animals re-exposed to the context where they had received electrical foot shocks 24 h before. The results indicate that the BNST is engaged in behavioral responses elicited by punished stimuli and aversively conditioned contexts, reinforcing its proposed role in anxiety. (C) 2008 IBRO. Published by Elsevier Ltd. All rights reserved.

Anti-inflammatory effects of red pepper (Capsicum baccatum) on carrageenan- and antigen-induced inflammation

Inflammation is a pivotal component of a variety of diseases, such as atherosclerosis and tumour progression. Various naturally occurring phytochemicals exhibit anti-inflammatory activity and are considered to be potential drug candidates against inflammation-related pathological processes. Capsicum baccatum L. var. pendulum (Willd.) Eshbaugh (Solanaceae) is the most consumed species in Brazil, and its compounds, such as capsaicinoids, have been found to inhibit the inflammatory process. However, the anti-inflammatory effects of C. baccatum have not been characterized. Thus, this study was designed to evaluate the effects of C. baccatum juice in animal models of acute inflammation induced by carrageenan and immune inflammation induced by methylated bovine serum albumin. Pretreatment (30 min) of rats with pepper juice (0.25-2.0 g kg(-1)) significantly decreased leucocyte and neutrophil migration, exudate volume and protein and LDH concentration in pleural exudates of a pleurisy model. This juice also inhibited neutrophil migration and reduced the vascular permeability on carrageenan-induced peritonitis in mice. C. baccatum juice also reduced neutrophil recruitment and exudate levels of pro-inflammatory cytokines TNF-alpha, and IL-1 beta in mouse inflammatory immune peritonitis. Furthermore, we demonstrated that the main constituent of C. baccatum juice, as extracted with chloroform, is capsaicin. In agreement with this, capsaicin was able to inhibit the neutrophil migration towards the inflammatory focus. To our knowledge, this is the first demonstration of the anti-inflammatory effect of C. baccatum juice and our data suggest that this effect may be induced by capsaicin. Moreover, the anti-inflammatory effect induced by red pepper may be by inhibition of pro-inflammatory cytokine production at the inflammatory site.

Quercetin does not alter lipopolysaccharide-induced fever in rats

Fever is considered an important component of the acute phase response of the body in defence against invading organisms such as bacteria. Quercetin, an important representative of the flavonoid class, has been extensively studied as an anti-inflammatory agent. In the present study, we investigated the effect of quercetin, administered orally (5, 25 and 50 mg kg(-1)) or intraperitoneally (50 mg kg(-1)), on the febrile response induced by either intraperitoneally (50 mu g kg(-1)) or intravenously (5 mu g kg(-1)) injected lipopolysaccharide (LPS from Escherichia coli) in rats. In contrast with the well known anti-inflammatory activity of quercetin, the results demonstrate that quercetin, at the doses used, did not alter the fever induced by LPS, regardless of the route of administration.

Cannabidiol inhibits the hyperphagia induced by cannabinoid-1 or serotonin-1A receptor agonists

Delta 9-THC is a component of Cannabis sativa that increases food intake in animals and humans, an effect prevented by selective CB1 receptor antagonists. Cannabidiol (CBD) is another constituent of this plant that promotes several opposite neuropharmacological effects compared to Delta 9-THC. CBD mechanisms of action are still not clear, but under specific experimental conditions it can antagonize the effects of cannabinoid agonists, block the reuptake of anandamide and act as an agonist of 5-HT1A receptors. Since both the cannabinoid and serotoninergic systems have been implicated in food intake control, the aim of the present work was to investigate the effects caused by CBD on hyperphagia induced by agonists of CB1 or 5-HT1A receptors. Fed or fasted Wistar rats received intraperitoneal (i.p.) injections of CBD (1, 10 and 20 mg/kg) and food intake was measured 30 min later for 1 h. Moreover, additional fed or fasted groups received, after pretreatment with CBD (20 mg/kg) or vehicle, i.p. administration of vehicle, a CBI receptor agonist WIN55,212-2 (2 mg/kg) or a 5-HT1A receptor agonist 8-OH-DPAT (1 mg/kg) and were submitted to the food intake test for 1 h. CBD by itself did not change food intake in fed or fasted rats. However, it prevented the hyperphagic effects induced by WIN55,212-2 or 8-OH-DPAT. These results show that CBD can interfere with food intake changes induced by a CB1 or 5-HT1A receptor agonist, suggesting that its role as a possible food intake regulator should be further investigate. (C) 2011 Elsevier Inc. All rights reserved.

IL-33 mediates antigen-induced cutaneous and articular hypernociception in mice

IL-33, a new member of the IL-1 family, signals through its receptor ST2 and induces T helper 2 (Th2) cytokine synthesis and mediates inflammatory response. We have investigated the role of IL-33 in antigen-induced hypernociception. Recombinant IL-33 induced cutaneous and articular mechanical hype rn ociception in a time- and dose-dependent manner. The hypernociception was inhibited by soluble (s) ST2 (a decoy receptor of IL-33), IL-1 receptor antagonist (IL-1ra), bosentan [a dual endothelin (ET)(A)/ETB receptor antagonist], clazosentan (an ETA receptor antagonist), or indomethacin (a cyclooxygenase inhibitor). IL-33 induced hypernociception in IL-18(-/-) mice but not in TNFR1(-/-) or IFN gamma(-/-) mice. The IL-33-induced hypernociception was not affected by blocking IL-15 or sympathetic amines (guanethidine). Furthermore, methylated BSA (mBSA)-induced cutaneous and articular mechanical hypernociception depended on TNFR1 and IFN gamma and was blocked by sST2, IL-1ra, bosentan, clazosentan, and indomethacin. mBSA also induced significant IL-33 and ST2 mRNA expression. Importantly, we showed that mBSA induced hypernociception via the IL-33 -> TNF alpha -> IL-1 beta -> IFN gamma -> ET-1 -> PGE(2) signaling cascade. These results therefore demonstrate that IL-33 is a key mediator of immune inflammatory hype rn ociception normally associated with a Th1 type of response, revealing a hitherto unrecognized function of IL-33 in a key immune pharmacological pathway that may be amenable to therapeutic intervention.

Modulation of mucosal immunity in a murine model of food-induced intestinal inflammation

Background Hypersensitivity or uncontrolled responses against dietary antigens can lead to inflammatory disorders like food allergy and current models reflect a variety of causes but do not reveal the detailed modulation of gut immunity in response to food antigens after breakdown in mucosal tolerance. Objective To develop and characterize a murine model for food-induced intestinal inflammation and to demonstrate the modulation of gut immune response by dietary allergenic antigens. Methods C57BL/6 mice were sensitized with peanut proteins, challenged with peanut seeds and their sera and gut segments were collected for subsequent analyses. Results Sensitization and challenged with peanut seeds led to alterations in gut architecture with inflammatory response characterized by oedema in lamina propria and cell infiltrate composed mainly by eosinophils, mast cells, phagocytes, natural killer and plasma cells, together with low percentage of gamma delta(+) and CD4(+)CD25(+)Foxp3(+) cells in Peyer`s patches. These animals also presented high levels of specific IgE and IgG1 in sera and modulation of mucosal immunity was mediated by increased expression of GATA-3, IL-4, IL-13 and TNF-alpha in contrast to low IFN-gamma in the gut. Conclusion A murine model for food-induced intestinal inflammation was characterized in which modulation of gut immunity occurs by peanut antigens in consequence of T-helper type 2 (Th2) allergic response and failure of regulatory mechanisms necessary for mucosa homeostasis, resembling food allergy. This work shed some light on the understanding of the pathogenesis of gastrointestinal disorders and intolerance in the gut and supports the development of therapies for food-related enteropathies like food allergy, focusing on gut-specific immune response.

Nitric Oxide-Induced Vasorelaxation in Response to PnTx2-6 Toxin from Phoneutria nigriventer Spider in Rat Cavernosal Tissue

Introduction. Priapism is one of several symptoms observed in accidental bites by the spider Phoneutria nigriventer. The venom of this spider is comprised of many toxins, and the majority has been shown to affect excitable ion channels, mainly sodium (Na+) channels. It has been demonstrated that PnTx2-6, a peptide extracted from the venom of P. nigriventer, causes erection in anesthetized rats and mice. Aim. We investigated the mechanism by which PnTx2-6 evokes relaxation in rat corpus cavernosum. Main Outcome Measures. PnTx2-6 toxin potentiates nitric oxide (NO)-dependent cavernosal relaxation. Methods. Rat cavernosal strips were incubated with bretylium (3 x 10-5 M) and contracted with phenylephrine (PE; 10-5 M). Relaxation responses were evoked by electrical field stimulation (EFS) or sodium nitroprusside (SNP) before and after 4 minutes of incubation with PnTx2-6 (10-8 M). The effect of PnTx2-6 on relaxation induced by EFS was also tested in the presence of atropine (10-6 M), a muscarinic receptor antagonist, N-type Ca2+ channel blockers (omega-conotoxin GVIA, 10-6 M) and sildenafil (3 x 10-8 M). Technetium99m radiolabeled PnTx2-6 subcutaneous injection was administrated in the penis. Results. Whereas relaxation induced by SNP was not affected by PnTx2-6, EFS-induced relaxation was significantly potentiated by this toxin as well as PnTx2-6 plus SNP. This potentiating effect was further increased by sildenafil, not altered by atropine, however was completely blocked by the N-type Ca2+ channels. High concentrated levels of radiolabeled PnTx2-6 was specifically found in the cavernosum tissue, suggesting PnTx2-6 is an important toxin responsible for P. nigriventer spider accident-induced priapism. Conclusion. We show that PnTx2-6 slows Na+ channels inactivation in nitrergic neurons, allowing Ca2+ influx to facilitate NO/cGMP signalling, which promotes increased NO production. In addition, this relaxation effect is independent of phosphodiesterase enzyme type 5 inhibition. Our data displays PnTx2-6 as possible pharmacological tool to study alternative treatments for erectile dysfunction. Nunes KP, Cordeiro MN, Richardson M, Borges MN, Diniz SOF, Cardoso VN, Tostes R, De Lima ME, Webb RC, and Leite R. Nitric oxide-induced vasorelaxation in response to PnTx2-6 toxin from Phoneutria nigriventer spider in rat cavernosal tissue. J Sex Med 2010;7:3879-3888.

Lipoxin A(4) attenuates zymosan-induced arthritis by modulating endothelin-1 and its effects

BACKGROUND AND PURPOSE Lipoxin A(4) (LXA(4)) is a lipid mediator involved in the resolution of inflammation. Increased levels of LXA(4) in synovial fluid and enhanced expression of the formyl peptide receptor 2/lipoxin A(4) receptor (FPR2/ALX) in the synovial tissues of rheumatoid arthritis patients have been reported. Endothelins (ETs) play a pivotal pro-inflammatory role in acute articular inflammatory responses. Here, we evaluated the anti-inflammatory role of LXA(4), during the acute phase of zymosan-induced arthritis, focusing on the modulation of ET-1 expression and its effects. EXPERIMENTAL APPROACH The anti-inflammatory effects of LXA(4), BML-111 (agonist of FPR2/ALX receptors) and acetylsalicylic acid (ASA) pre- and post-treatments were investigated in a murine model of zymosan-induced arthritis. Articular inflammation was assessed by examining knee joint oedema; neutrophil accumulation in synovial cavities; and levels of prepro-ET-1 mRNA, leukotriene (LT)B(4), tumour necrosis factor (TNF)-alpha and the chemokine KC/CXCL1, after stimulation. The direct effect of LXA(4) on ET-1-induced neutrophil activation and chemotaxis was evaluated by shape change and Boyden chamber assays respectively. KEY RESULTS LXA(4), BML-111 and ASA administered as pre- or post-treatment inhibited oedema and neutrophil influx induced by zymosan stimulation. Zymosan-induced preproET-1 mRNA, KC/CXCL1, LTB(4) and TNF-alpha levels were also decreased after LXA(4) pretreatment. In vitro, ET-1-induced neutrophil chemotaxis was inhibited by LXA4 pretreatment. LXA(4) treatment also inhibited ET-1-induced oedema formation and neutrophil influx into mouse knee joints. CONCLUSION AND IMPLICATION LXA(4) exerted anti-inflammatory effects on articular inflammation through a mechanism that involved the inhibition of ET-1 expression and its effects.

Involvement of the prelimbic prefrontal cortex on cannabidiol-induced attenuation of contextual conditioned fear in rats

Rationale: Systemic administration of cannabidiol (CBD), a non-psychotomimetic component of Cannabis sativa, is able to attenuate cardiovascular and behavioral (freezing) changes induced by re-exposure to a context that had been previously paired with footshocks. The brain sites mediating this effect, however, remain unknown. The medial prefrontal cortex (mPFC) has been related to contextual fear conditioning. Objectives: (1) To verify, using c-Fos immunocytochemistry, if the mPFC is involved in the attenuation of contextual fear induced by systemic administration of CBD; (2) to investigate if direct microinjections of CBD into mPFC regions would also attenuate contextual fear. Results: Confirming previous results systemic administration of CBD (10 mg/kg) decreased contextual fear and associated c-Fos expression in the prefrontal cortex (prelimbic and infralimbic regions). The drug also attenuated c-Fos expression in the bed nucleus of the stria terminalis (BNST). Direct CBD (30 nmol) microinjection into the PL prefrontal cortex reduced freezing induced by re-exposure to the aversively conditioned context. In the infralimbic (IL) prefrontal cortex, however, CBD (30 nmol) produced an opposite result, increasing the expression of contextual fear conditioning. This result was confirmed by an additional experiment where the conditioning session was performed under a less aversive protocol. Conclusion: These results suggest that the PL prefrontal cortex may be involved in the attenuation of contextual fear induced by systemic injection of CBD. They also support the proposition that the IL and PL play opposite roles in fear conditioning. A possible involvement of the BNST in CBD effects needs to be further investigated. (C) 2009 Elsevier B.V. All rights reserved.

Uridine adenosine tetraphosphate-induced contraction is increased in renal but not pulmonary arteries from DOCA-salt hypertensive rats

Matsumoto T, Tostes RC, Webb RC. Uridine adenosine tetraphosphate-induced contraction is increased in renal but not pulmonary arteries from DOCA-salt hypertensive rats. Am J Physiol Heart Circ Physiol 301: H409-H417, 2011. First published May 6, 2011; doi:10.1152/ajpheart.00084.2011.-Uridine adenosine tetraphosphate (Up(4)A) was reported as a novel endothelium-derived contracting factor. Up(4)A contains both purine and pyrimidine moieties, which activate purinergic (P2)X and P2Y receptors. However, alterations in the vasoconstrictor responses to Up(4)A in hypertensive states remain unclear. The present study examined the effects of Up(4)A on contraction of isolated renal arteries (RA) and pulmonary arteries (PA) from DOCA-salt rats using isometric tension recording. RA from DOCA-salt rats exhibited increased contraction to Up(4)A versus arteries from control uninephrectomized rats in the absence and presence of N(G)-nitro-L-arginine (nitric oxide synthase inhibitor). On the other hand, the Up(4)A-induced contraction in PA was similar between the two groups. Up(4)A-induced contraction was inhibited by suramin (nonselective P2 antagonist) but not by diinosine pentaphosphate pentasodium salt hydrate (Ip5I; P2X(1) antagonist) in RA from both groups. Furthermore, 2-thiouridine 5`-triphosphate tetrasodium salt (2-Thio-UTP; P2Y(2) agonist)-, uridine-5`-(gamma-thio)-triphosphate trisodium salt (UTP gamma S; P2Y(2)/P2Y(4) agonist)-, and 5-iodouridine-5`-O-diphosphate trisodium salt (MRS 2693; P2Y(6) agonist)-induced contractions were all increased in RA from DOCA-salt rats. Protein expression of P2Y(2)-, P2Y(4)-, and P2Y(6) receptors in RA was similar between the two groups. In DOCA-salt RA, the enhanced Up(4)A-induced contraction was reduced by PD98059, an ERK pathway inhibitor, and Up(4)Astimulated ERK activation was increased. These data are the first to indicate that Up(4)A-induced contraction is enhanced in RA from DOCA-salt rats. Enhanced P2Y receptor signaling and activation of the ERK pathway together represent a likely mechanism mediating the enhanced Up(4)A-induced contraction. Up(4)A might be of relevance in the pathophysiology of vascular tone regulation and renal dysfunction in arterial hypertension.

GABA(A) receptor blockade in dorsomedial and ventromedial nuclei of the hypothalamus evokes panic-like elaborated defensive behaviour followed by innate fear-induced antinociception

Dysfunction in the hypothalamic GABAergic system has been implicated in panic syndrome in humans. Furthermore, several studies have implicated the hypothalamus in the elaboration of pain modulation. Panic-prone states are able to be experimentally induced in laboratory animals to study this phenomenon. The aim of the present work was to investigate the involvement of medial hypothalamic nuclei in the organization of panic-like behaviour and the innate fear-induced oscillations of nociceptive thresholds. The blockade of GABA(A) receptors in the neuronal substrates of the ventromedial. or dorsomedial hypothalamus was followed by elaborated defensive panic-like reactions. Moreover, innate fear-induced antinociception was consistently elicited after the escape behaviour. The escape responses organized by the dorsomedial and ventromedial hypothalamic nuclei were characteristically more elaborated, and a remarkable exploratory behaviour was recorded during GABA(A) receptor blockade in the medial hypothalamus. The motor characteristic of the elaborated defensive escape behaviour and the patterns of defensive alertness and defensive immobility induced by microinjection of the bicuculline either into the dorsomedial. or into the ventromedial hypothalamus were very similar. This was followed by the same pattern of innate fear-induced antinociceptive response that lasted approximately 40 min after the elaborated defensive escape reaction in both cases. These findings suggest that dysfunction of the GABA-mediated neuronal system in the medial hypothalamus causes panic-like responses in laboratory animals, and that the elaborated escape behaviour organized in both dorsomedial and ventromedial hypothalamic nuclei are followed by significant innate-fear-induced antinociception. Our findings indicate that the GABA(A) receptor of dorsomedial and ventromedial hypothalamic nuclei are critically involved in the modulation of panic-like behaviour. (C) 2009 Elsevier B.V. All rights reserved.

Anxiolytic-like effects induced by blockade of transient receptor potential vanilloid type 1 (TRPV1) channels in the medial prefrontal cortex of rats

The endocannabinoid anandamide, in addition to activating cannabinoid type 1 receptors (CB1), may act as an agonist at transient receptor potential vanilloid type 1 (TRPV1) channels. In the periaqueductal gray, CB1 activation inhibits, whereas TRPV1 increases, anxiety-like behavior. In the medial prefrontal cortex (mPFC), another brain region related to defensive responses, CB1 activation induces anxiolytic-like effects. However, a possible involvement of TRPV1 is still unclear. In the present study, we tested the hypothesis that TRPV1 channel contributes to the modulation of anxiety-like behavior in the mPFC. Male Wistar rats (n = 5-7 per group) received microinjections of the TRPV1 antagonist capsazepine (1-60 nmol) in the ventral portion of the mPFC and were exposed to the elevated plus maze (EPM) or to the Vogel conflict test. Capsazepine increased exploration of open arms in the EPM as well as the number of punished licks in the Vogel conflict test, suggesting anxiolytic-like effects. No changes in the number of entries into the enclosed arms were observed in the EPM, indicating that there were no changes in motor activity. Moreover, capsazepine did not interfere with water consumption or nociceptive threshold, discarding potential confounding factors for the Vogel conflict test. These data suggest that TRPV1 in the ventral mPFC tonically inhibits anxiety-like behavior. TRPV1 could facilitate defensive responses opposing, therefore, the anxiolytic-like effects reported after local activation of CB1 receptors.

Leptin resistance and desensitization of hypophagia during prolonged inflammatory challenge

Leptin resistance and desensitization of hypophagia during prolonged inflammatory challenge. Am J Physiol Endocrinol Metab 300: E858-E869, 2011. First published February 22, 2011; doi: 10.1152/ajpendo.00558.2010.-Acute exposure to bacterial lipopolysaccharide (LPS) is a potent inducer of immune response as well as hypophagia. Nevertheless, desensitization of responses to LPS occurs during long-term exposure to endotoxin. We induced endotoxin tolerance, injecting repeated (6LPS) LPS doses compared with single (1LPS) treatment. 1LPS, but not 6LPS group, showed decreased food intake and body weight, which was associated with an increased plasma leptin and higher mRNA expression of OB-Rb, MC4R, and SOCS3 in the hypothalamus. Hypophagia induced by 1LPS was associated with lower levels of 2-arachidonoylglycerol (2-AG), increased number of p-STAT3 neurons, and decreased AMP-activated protein kinase (AMPK) activity. Desensitization of hypophagia in the 6LPS group was related to high 2-AG, with no changes in p-STAT3 or increased p-AMPK. Leptin decreased food intake, body weight, 2-AG levels, and AMPK activity and enhanced p-STAT3 in control rats. However, leptin had no effects on 2-AG, p-STAT3, or p-AMPK in the 1LPS and 6LPS groups. Rats treated with HFD to induce leptin resistance showed neither hypophagia nor changes in p-STAT3 after 1LPS, suggesting that leptin and LPS recruit a common signaling pathway in the hypothalamus to modulate food intake reduction. Desensitization of hypophagia in response to repeated exposure to endotoxin is related to an inability of leptin to inhibit AMPK phosphorylation and 2-AG production and activate STAT3. SOCS3 is unlikely to underlie this resistance to leptin signaling in the endotoxin tolerance. The present model of prolonged inflammatory challenge may contribute to further investigations on mechanisms of leptin resistance.

Cholecystokinin and hypothalamic corticotrophin-releasing factor participate in endotoxin-induced hypophagia

Cholecystokinin (CCK) provides a meal-related signal that activates brainstem neurons, which have reciprocal interconnections with the hypothalamic paraventricular nucleus. Neurons that express corticotrophin-releasing factor (CRF) in the hypothalamus possess anorexigenic effects and are activated during endotoxaemia. This study investigated the effects of CCK(1) receptor blockade on lipopolysaccharide (LPS)-induced hypophagia and hypothalamic CRF neuronal activation. Male Wistar rats were pretreated with a specific CCK(1) receptor antagonist (devazepide; 1 mg kg(-1); I.P.) or vehicle; 30 min later they received LPS (100 mu g kg(-1); I.P.) or saline injection. Food intake, corticosterone responses and Fos-CRF and Fos-alpha-melanocyte-stimulating hormone (alpha-MSH) immunoreactivity in the hypothalamus and Fos-tyrosine hydroxylase immunoreactivity in the nucleus of the solitary tract (NTS) were evaluated. In comparison with saline treatment, LPS administration decreased food intake and increased plasma corticosterone levels, as well as the number of Fos-CRF and Fos-tyrosine hydroxylase double-labelled neurons in vehicle-pretreated rats; no change in Fos-alpha-MSH immunoreactivity was observed after LPS injection. In saline-treated animals, devazepide pretreatment increased food intake, but it did not modify other parameters compared with vehicle-pretreated rats. Devazepide pretreatment partly reversed LPS-induced hypophagia and Fos-CRF and brainstem neuronal activation. Devazepide did not modify the corticosterone and Fos-alpha-MSH responses in rats treated with LPS. In conclusion, the present data suggest that LPS-induced hypophagia is mediated at least in part by CCK effects, via CCK(1) receptor, on NTS and hypothalamic CRF neurons.