No abstract

The orexin-immunoreactive neurons are part of an important arousal-promoting hypothalamic population. Several groups have investigated these neurons during the lactation period, when numerous physiological alterations occur in the dam's body to cope with the newly acquired metabolic needs of the litter. Although those studies have probed this population during the early and intermediate stages of lactation, few works have examined its response to weaning, including the cessation of the tactile suckling stimulus as the litter stops nursing. Using double immunohistochemistry for orexin and FOS combined with three-dimensional reconstruction techniques, we investigated orexin-synthesizing neurons and their activation at different times during weaning, in addition to the role played by the suckling stimulus. We report here that weaning promoted a decline in the anterior population of orexin-immunoreactive neurons and decreased the number of double orexin-FOS neurons labeled in the central dorsomedial hypothalamus, in addition to reducing the overall number of FOS-immunoreactive cells in the whole tuberal hypothalamus. Disruption of the suckling stimulus from the pups impaired the decrease in the number of anteriorly located orexin-immunoreactive neurons, attenuated the activation of orexin-synthesizing cells in the dorsomedial hypothalamus and reduced the number of FOS-immunoreactive neurons across the tuberal hypothalamus. When taken together, our data suggest that the weaning period is necessary to restore neurochemical pathways altered during the lactation period and that the suckling stimulus plays a significant role in this process.

The present work investigated the possible relationship between central and peripheral oxytocin (OT) release during milking in experimental ewes. Ten multiparous ewes were divided into four groups according to milk ejection stimuli: exclusive machine milking (EM), mixed-management milking and suckling, lambs separated during the night and reunited with their mother after morning milking (MMS); mixed-management with manual milking (MMM), and exclusive suckling (ES) lambs also separated during the night. Simultaneous sampling of cerebrospinal fluid (CSF) and blood was performed during milking. The means, standard deviations, variation coefficients, and minimum and maximum CSF and plasma OT concentrations were the following, respectively: 257.88 ± 265.90 pg/ml, 103.11%, and 11.70 and 1000.00 pg/ml. No statistically significant correlations were found between OT concentrations in the CSF and plasma samples (EM: -0.26; ES: -0.19; MMM: 0.05; MMS: 0.04). The OT concentration in CSF was not influenced by milk ejection stimuli, although plasma OT was higher in the MMM (679.80 ± 25.63) and MMS (591.82 ± 30.56) groups compared with the EM and ES groups. Additionally, plasma OT concentrations were higher in the OME group (381.04 ± 22.09) compared with the AE group (218.82 ± 27.04). In conclusion, no positive correlations were found between central and peripheral OT concentrations during milking and suckling. Plasma OT concentrations differed as a function of milking management and had consequences for both milk ejection and production. Plasma but not CSF oxytocin concentrations were influenced by different milk ejection stimuli.Keywords: Catheterization. Milk ejection. Cerebrospinal fluid. Sheep. Lactation. ResumoFoi investigada a possível relação entre as concentrações de ocitocina no líquido cefalorraquidiano e no soro em diferentes formas de ordenha em ovinos. Foram utilizadas dez ovelhas multíparas, divididas em quatro grupos de acordo com o estímulo para ejeção do leite: ordenha exclusivamente mecânica (EM), ordenha mista mecânica e mamada com os carneiros separados das mães durante a noite e reunidos a elas pela manhã para amamentação (MMS); ordenha mista com ordenha manual (MMS); apenas amamentação natural (ES). Foram coletadas amostras de fluido cerebroespinhal e de sangue, simultaneamente, durante as ordenhas. A média, o coeficiente de variação e os valores máximos e mínimos de ocitocina do plasma foram respectivamente 257,88 ± 265,90 pg/ml, 103,11%, e 11,70 e 1000,00 pg/ml. Não foram encontradas correlações entre as concentrações centrais e plasmáticas de ocitocina (EM: -0,26; ES: -0,19; MMM: 0,05; MMS: 0,04). Não foi evidenciada influência do tipo de estímulo para ejeção do leite nas concentrações centrais de ocitocina. Entretanto, as concentrações plasmáticas de ocitocina foram maiores nos grupos MMM (679,80 ± 25,63) e MMS (591,82 ± 30,56), quando comparadas às dos grupos EM e ES. Além disso, as concentrações plasmáticas de ocitocina foram maiores no grupo de OME (381,04 ± 22,09) em relação ao grupo AE (...

(FAPESP) pelo fornecimento da bolsa de mestrado (2010/14469-2), fundamental para o desenvolvimento técnico e intelectual deste projeto. "Saber muito não lhe torna inteligente. A inteligência se traduz na forma que você recolhe, julga, maneja e, sobretudo, onde e como aplica esta informação."

The present work investigated the possible relationship between central and peripheral oxytocin (OT) release during milking in experimental ewes. Ten multiparous ewes were divided into four groups according to milk ejection stimuli: exclusive machine milking (EM), mixed-management milking and suckling, lambs separated during the night and reunited with their mother after morning milking (MMS); mixed-management with manual milking (MMM), and exclusive suckling (ES) lambs also separated during the night. Simultaneous sampling of cerebrospinal fluid (CSF) and blood was performed during milking. The means, standard deviations, variation coefficients, and minimum and maximum CSF and plasma OT concentrations were the following, respectively: 257.88 ± 265.90 pg/ml, 103.11%, and 11.70 and 1000.00 pg/ml. No statistically significant correlations were found between OT concentrations in the CSF and plasma samples (EM: -0.26; ES: -0.19; MMM: 0.05; MMS: 0.04). The OT concentration in CSF was not influenced by milk ejection stimuli, although plasma OT was higher in the MMM (679.80 ± 25.63) and MMS (591.82 ± 30.56) groups compared with the EM and ES groups. Additionally, plasma OT concentrations were higher in the OME group (381.04 ± 22.09) compared with the AE group (218.82 ± 27.04). In conclusion, no positive correlations were found between central and peripheral OT concentrations during milking and suckling. Plasma OT concentrations differed as a function of milking management and had consequences for both milk ejection and production. Plasma but not CSF oxytocin concentrations were influenced by different milk ejection stimuli.Keywords: Catheterization. Milk ejection. Cerebrospinal fluid. Sheep. Lactation. ResumoFoi investigada a possível relação entre as concentrações de ocitocina no líquido cefalorraquidiano e no soro em diferentes formas de ordenha em ovinos. Foram utilizadas dez ovelhas multíparas, divididas em quatro grupos de acordo com o estímulo para ejeção do leite: ordenha exclusivamente mecânica (EM), ordenha mista mecânica e mamada com os carneiros separados das mães durante a noite e reunidos a elas pela manhã para amamentação (MMS); ordenha mista com ordenha manual (MMS); apenas amamentação natural (ES). Foram coletadas amostras de fluido cerebroespinhal e de sangue, simultaneamente, durante as ordenhas. A média, o coeficiente de variação e os valores máximos e mínimos de ocitocina do plasma foram respectivamente 257,88 ± 265,90 pg/ml, 103,11%, e 11,70 e 1000,00 pg/ml. Não foram encontradas correlações entre as concentrações centrais e plasmáticas de ocitocina (EM: -0,26; ES: -0,19; MMM: 0,05; MMS: 0,04). Não foi evidenciada influência do tipo de estímulo para ejeção do leite nas concentrações centrais de ocitocina. Entretanto, as concentrações plasmáticas de ocitocina foram maiores nos grupos MMM (679,80 ± 25,63) e MMS (591,82 ± 30,56), quando comparadas às dos grupos EM e ES. Além disso, as concentrações plasmáticas de ocitocina foram maiores no grupo de OME (381,04 ± 22,09) em relação ao grupo AE (...