Acute High Fat Diet Consumption Activates the Mesolimbic Circuit and Requires Orexin Signaling in a Mouse Model

Overconsumption of palatable energy-dense foods has negative health implications and it is associated with obesity andseveral eating disorders. Currently, little is known about the neuronal circuitries activated by the acute ingestion of arewarding stimulus. Here, we used a combination of immunohistochemistry, pharmacology and neuronal tracing analysesto examine the role of the mesolimbic system in general, and the orexin neurons in particular, in a simple experimental testin which naı ̈ve mice are allowed to spontaneously eat a pellet of a high fat diet (HFD) for 2 h. We found that acute HFDactivates c-Fos expression in several reward-related brain areas, including the ventral tegmental area (VTA), nucleusaccumbens, central amygdala and lateral hypothalamic area. We also found that: i- HFD-mediated orosensory stimulationwas required for the mesolimbic pathway activation, ii- acute HFD differentially activates dopamine neurons of theparanigral, parabrachial pigmented and interfascicular sub-regions of the VTA, and iii- orexin neurons of the lateralhypothalamic area are responsive to acute HFD. Moreover, orexin signaling blockade, with the orexin 1 receptor antagonistSB-334867, reduces acute HFD consumption and c-Fos induction in the VTA but not in the other mesolimbic nuclei understudy. Finally, we found that most orexin neurons responsive to acute HFD innervate the VTA. Our results show that acuteHFD consumption recruits the mesolimbic system and that the full manifestation of this eating behavior requires theactivation of orexin signaling.Fil: Valdivia Torres, Lesly Spring. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Patrone, Anabela. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Reynaldo, Mirta Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Perello, Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; Argentin

Acute High Fat Diet Consumption Activates the Mesolimbic Circuit and Requires Orexin Signaling in a Mouse Model

Overconsumption of palatable energy-dense foods has negative health implications and it is associated with obesity andseveral eating disorders. Currently, little is known about the neuronal circuitries activated by the acute ingestion of arewarding stimulus. Here, we used a combination of immunohistochemistry, pharmacology and neuronal tracing analysesto examine the role of the mesolimbic system in general, and the orexin neurons in particular, in a simple experimental testin which naı ̈ve mice are allowed to spontaneously eat a pellet of a high fat diet (HFD) for 2 h. We found that acute HFDactivates c-Fos expression in several reward-related brain areas, including the ventral tegmental area (VTA), nucleusaccumbens, central amygdala and lateral hypothalamic area. We also found that: i- HFD-mediated orosensory stimulationwas required for the mesolimbic pathway activation, ii- acute HFD differentially activates dopamine neurons of theparanigral, parabrachial pigmented and interfascicular sub-regions of the VTA, and iii- orexin neurons of the lateralhypothalamic area are responsive to acute HFD. Moreover, orexin signaling blockade, with the orexin 1 receptor antagonistSB-334867, reduces acute HFD consumption and c-Fos induction in the VTA but not in the other mesolimbic nuclei understudy. Finally, we found that most orexin neurons responsive to acute HFD innervate the VTA. Our results show that acuteHFD consumption recruits the mesolimbic system and that the full manifestation of this eating behavior requires theactivation of orexin signaling.Facultad de Ciencias ExactasInstituto Multidisciplinario de Biología Celula

Escalation in high fat intake in a binge eating model differentially engages dopamine neurons of the ventral tegmental area and requires ghrelin signaling

Binge eating is a behavior observed in a variety of human eating disorders. Ad libitum fed rodents daily and time-limited exposed to a high-fat diet (HFD) display robust binge eating events that gradually escalate over the initial accesses. Intake escalation is proposed to be part of the transition from a controlled to a compulsive or loss of control behavior. Here, we used a combination of behavioral and neuroanatomical studies in mice daily and time-limited exposed to HFD to determine the neuronal brain targets that are activated – as indicated by the marker of cellular activation c-Fos – under these circumstances. Also, we used pharmacologically or genetically manipulated mice to study the role of orexin or ghrelin signaling, respectively, in the modulation of this behavior. We found that four daily and time-limited accesses to HFD induce: (i) a robust hyperphagia with an escalating profile, (ii) an activation of different sub-populations of the ventral tegmental area dopamine neurons and accumbens neurons that is, in general, more pronounced than the activation observed after a single HFD consumption event, and (iii) an activation of the hypothalamic orexin neurons, although orexin signaling blockage fails to affect escalation of HFD intake. In addition, we found that ghrelin receptor-deficient mice fail to both escalate the HFD consumption over the successive days of exposure and fully induce activation of the mesolimbic pathway in response to HFD consumption. Current data suggest that the escalation in high fat intake during repeated accesses differentially engages dopamine neurons of the ventral tegmental area and requires ghrelin signaling

Actividad antimicrobiana de germicidas halogenados frente a aislamientos hospitalarios

Antiseptics and disinfectants are extensively used in hospitals and health care settings for a variety of topical and hard-surface applications. In particular, they are essential part of infection control practices and in the prevention of nosocomial infections. Despite this, few is known about the mode of action of these biocides with respect to antibiotics. In general, the antimicrobial activity can be influenced by many factors such as formulation effects, presence of organic matter, synergy, temperature, dilution and test method. The widespread use of antiseptics and disinfectant products has prompted some speculation on the development of microbial resistance, in particular cross-resistance to antibiotics. The aim of this study was to evaluate microbiological resistance to halogenated compounds by studying the behaviour of the grampositive and gramnegative clinical isolates against halogenated biocides usually applied, with and without organic substance and applying distilled water, potable water and water of 300 ppm hardness as dilution means. The results indicate that the hospital microorganisms show a higher resistance to the biocides than the strain Staphylococcus aureus ATCC 6538, although the effective concentration in clean conditions was lesser than the recommended ones, for all the dilution means. In presence of organic matter the antimicrobial activity was reduced in accordance with the bactericidal concentration of each microorganisrn, due to the oxidant action of these disinfectantsLos antisépticos y desinfectantes se emplean en hospitales para una gran variedad de aplicaciones, tanto tópicas como sobre superficies. Estos compuestos son esenciales en el control y la prevención de las infecciones nosocomiales. A pesar de esto, se conoce bastante menos acerca del modo de acción de estos biocidas que de los antibióticos habitualmente empleados en terapéutica. La actividad antimicrobiana puede ser influenciada por muchos factores tales como la formulación, la presencia de materia orgánica, efectos de sinergia, temperatura, dilución e incluso del método de ensayo. El uso tan difundido de productos desinfectantes y antisépticos ha llevado a algunas especulaciones sobre el desarrollo de resistencia microbiana, y particularmente, resistencia cruzada con antibióticos. Con el propósito de estudiar la resistencia microbiana a germicidas halogenados de uso corriente en ,centros asistenciales, se evaluó el comportamiento de aislamientos hospitalarios tanto gram negativos como gram positivos frente a soluciones de hipoclorito de sodio, iodopovidona y tintura de iodo en presencia y ausencia de sustancias interferentes tales como materia orgánica y cationes. Los multados obtenidos indican que los microorganismos hospitalarios presentan mayor resistencia a los bioddas analizados con respecto al microorganismo de ref- erencia Staphylococcus aureus ATCC 6538. Sin embargo, en condiciones limpias este grupe de biocidas posee una alta eficacia, aún muy por debajo de las concentraciones de uso recomendadas, para todos los medios de dilución estudiados. Con la presencia de materia orgánica la actividad germicida disminuyó en todos los casos en relación directamente proporcional a la concentración, debido a la naturaleza predominantemente oxidante de estos compuestos

Neuroanatomical and functional characterization of CRF neurons of the amygdala using a novel transgenic mouse model

The corticotropin-releasing factor (CRF)-producing neurons of the amygdala have been implicated in behavioral and physiological responses associated with fear, anxiety, stress, food intake and reward. To overcome the difficulties in identifying CRF neurons within the amygdala, a novel transgenic mouse line, in which the humanized recombinant Renilla reniformis green fluorescent protein (hrGFP) is under the control of the CRF promoter (CRF-hrGFP mice), was developed. First, the CRF-hrGFP mouse model was validated and the localization of CRF neurons within the amygdala was systematically mapped. Amygdalar hrGFP-expressing neurons were located primarily in the interstitial nucleus of the posterior limb of the anterior commissure, but also present in the central amygdala. Secondly, the marker of neuronal activation c-Fos was used to explore the response of amygdalar CRF neurons in CRF-hrGFP mice under different experimental paradigms. C-Fos induction was observed in CRF neurons of CRF-hrGFP mice exposed to an acute social defeat stress event, a fasting/refeeding paradigm or lipopolysaccharide (LPS) administration. In contrast, no c-Fos induction was detected in CRF neurons of CRF-hrGFP mice exposed to restraint stress, forced swimming test, 48-h fasting, acute high-fat diet (HFD) consumption, intermittent HFD consumption, ad libitum HFD consumption, HFD withdrawal, conditioned HFD aversion, ghrelin administration or melanocortin 4 receptor agonist administration. Thus, this study fully characterizes the distribution of amygdala CRF neurons in mice and suggests that they are involved in some, but not all, stress or food intake-related behaviors recruiting the amygdala

Growth hormone secretagogue receptor in dopamine neurons controls appetitive and consummatory behaviors towards high-fat diet in ad-libitum fed mice

Growth hormone secretagogue receptor (GHSR), the receptor for ghrelin, is expressed in key brain nuclei that regulate food intake. The dopamine (DA) pathways have long been recognized to play key roles mediating GHSR effects on feeding behaviors. Here, we aimed to determine the role of GHSR in DA neurons controlling appetitive and consummatory behaviors towards high fat (HF) diet. For this purpose, we crossed reactivable GHSR-deficient mice with DA transporter (DAT)-Cre mice, which express Cre recombinase under the DAT promoter that is active exclusively in DA neurons, to generate mice with GHSR expression limited to DA neurons (DAT-GHSR mice). We found that DAT-GHSR mice show an increase of c-Fos levels in brain areas containing DA neurons after ghrelin treatment, in a similar fashion as seen in wild-type mice; however, they did not increase food intake or locomotor activity in response to systemically- or centrally-administered ghrelin. In addition, we found that satiated DAT-GHSR mice displayed both anticipatory activity to scheduled HF diet exposure and HF intake in a binge-like eating protocol similar to those in wild-type mice, whereas GHSR-deficient mice displayed impaired responses. We conclude that GHSR expression in DA neurons is sufficient to both mediate increased anticipatory activity to a scheduled HF diet exposure and fully orchestrate binge-like HF intake, but it is insufficient to restore the acute orexigenic or locomotor effects of ghrelin treatment. Thus, GHSR in DA neurons affects appetitive and consummatory behaviors towards HF diet that take place in the absence of caloric needs.Fil: Cornejo, María Paula. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Barrile, Franco. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Cassano, Daniela Alejandra. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Aguggia, Julieta Paola. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Garcia Romero, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Reynaldo, Mirta Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Andreoli, Maria Florencia. Provincia de Buenos Aires. Ministerio de Salud. Hospital de Niños "Sor María Ludovica" de La Plata. Instituto de Desarrollo e Investigaciones Pediátricas; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata; ArgentinaFil: de Francesco, Pablo Nicolás. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; ArgentinaFil: Perello, Mario. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - La Plata. Instituto Multidisciplinario de Biología Celular. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Instituto Multidisciplinario de Biología Celular. Universidad Nacional de La Plata. Instituto Multidisciplinario de Biología Celular; Argentin

Circulating ghrelin acts on GABA neurons of the area postrema and mediates gastric emptying in male mice

Ghrelin is known to act on the area postrema (AP), a sensory circumventricular organ located in the medulla oblongata that regulates a variety of important physiological functions. However, the neuronal targets of ghrelin in the AP and their potential role are currently unknown. In this study, we used wild-type and genetically modified mice to gain insights into the neurons of the AP expressing the ghrelin receptor [growth hormone secretagogue receptor (GHSR)] and their role. We show that circulating ghrelin mainly accesses the AP but not to the adjacent nucleus of the solitary tract. Also, we show that both peripheral administration of ghrelin and fasting induce an increase of c-Fos, a marker of neuronal activation, in GHSR-expressing neurons of the AP, and that GHSR expression is necessary for the fasting-induced activation of AP neurons. Additionally, we show that ghrelin-sensitive neurons of the AP are mainly γ-aminobutyric acid (GABA)ergic, and that an intact AP is required for ghrelin-induced gastric emptying. Overall, we show that the capacity of circulating ghrelin to acutely induce gastric emptying in mice requires the integrity of the AP, which contains a population of GABA neurons that are a target of plasma ghrelin.Instituto Multidisciplinario de Biología CelularFacultad de Ciencias Veterinaria

Ghrelin receptor signaling targets segregated clusters of neurons within the nucleus of the solitary tract

Ghrelin is a stomach-derived hormone that regulates a variety of biological functions such as food intake, gastrointestinal function and blood glucose metabolism, among others. Ghrelin acts via the growth hormone secretagogue receptor (GHSR), a G-protein-coupled receptor located in key brain areas that mediate specific actions of the hormone. GHSR is highly expressed in the nucleus of the solitary tract (NTS), which is located in the medulla oblongata and controls essential functions, including orofacial, autonomic, neuroendocrine and behavioral responses. Here, we used a mouse model, in which the expression of enhanced green fluorescent protein (eGFP) is controlled by the promoter of GHSR (GHSR-eGFP mice), to gain neuroanatomical and functional insights of the GHSR-expressing neurons of the NTS. We found that GHSR-expressing neurons of the NTS are segregated in clusters that were symmetrically distributed to the midline: (1) a pair of rostral clusters, and (2) a caudal and medially located cluster. We also identified that a subset of GHSR neurons of the caudal NTS are GABAergic. Finally, we found that rostral NTS GHSR neurons increase the levels of the marker of neuronal activation c-Fos in mice exposed to fasting/refeeding or high-fat diet bingeing protocols, while caudal NTS GHSR neurons increase the levels of c-Fos in mice exposed to gastric distension or LiCl-induced malaise protocols. Thus, current data provide evidence that ghrelin receptor signaling seems to target segregated clusters of neurons within the NTS that, in turn, may be activated by different stimuli.Instituto Multidisciplinario de Biología CelularFacultad de Ciencias Veterinaria

Circulating ghrelin acts on GABA neurons of the area postrema and mediates gastric emptying in male mice

Ghrelin is known to act on the area postrema (AP), a sensory circumventricular organ located in the medulla oblongata that regulates a variety of important physiological functions. However, the neuronal targets of ghrelin in the AP and their potential role are currently unknown. In this study, we used wild-type and genetically modified mice to gain insights into the neurons of the AP expressing the ghrelin receptor [growth hormone secretagogue receptor (GHSR)] and their role. We show that circulating ghrelin mainly accesses the AP but not to the adjacent nucleus of the solitary tract. Also, we show that both peripheral administration of ghrelin and fasting induce an increase of c-Fos, a marker of neuronal activation, in GHSR-expressing neurons of the AP, and that GHSR expression is necessary for the fasting-induced activation of AP neurons. Additionally, we show that ghrelin-sensitive neurons of the AP are mainly γ-aminobutyric acid (GABA)ergic, and that an intact AP is required for ghrelin-induced gastric emptying. Overall, we show that the capacity of circulating ghrelin to acutely induce gastric emptying in mice requires the integrity of the AP, which contains a population of GABA neurons that are a target of plasma ghrelin.Instituto Multidisciplinario de Biología CelularFacultad de Ciencias Veterinaria