Respostas do sistema MCHérgico à privação e restrição de sono em ratos
Data
2014-07-30
Autores
Agamme, Ana Luiza Dias Abdo 
Orientadores
Almeida, Vania D'Almeida
Tipo
Dissertação de mestrado
Título da Revista
ISSN da Revista
Título de Volume
Resumo
No hipotálamo existem neurônios que utilizam MCH (hormônio concentrador de melanina) como neuromoduladores. Esses neurônios projetam-se através do sistema nervoso central e possuem funções fisiológicas importantes; diversos estudos experimentais sugerem que o MCH atue na promoção do sono. Sendo assim, tivemos como objetivo investigar os efeitos da privação de sono, rebote e restrição de sono sobre o sistema MCHérgico em dois momentos do ciclo claro/escuro (ZT0 e ZT8).Para isso, nós quantificamos os níveis de MCH no líquor em ratos após privação de sono paradoxal (PS), rebote (RB) e restrição de sono (RS) durante o dia subjetivo (Zeitgeber time – ZT8, quando ocorrem maiores concentrações de sono ) e no final da noite subjetiva (ZT0, horário em que acendem as luzes do biotério, final da fase escura). Na condição controle (sono e vigília ad libitum), não houve diferença nos níveis de MCH no líquor entre ZT8 e ZT0. Entretanto, quando o sono foi perturbado, uma diferença significante foi observada. Além disso, quando o líquor foi coletado em ZT0, os níveis de MCH aumentaram significantemente no grupo RB 96 comparado ao CT. Quando as coletas de líquor foram realizadas em ZT8, o grupo RS apresentou aumento significante nos níveis de MCH em comparação ao CT, PS 96 e PS 120. A fim de obter informações sobre a relação entre os níveis de MCH no líquor (proteína circulante) e a expressão de genes a ele relacionados no cérebro, nós investigamos a expressão do precursor de MCH (Pmch) no hipotálamo e do receptor 1 (Mchr1) no córtex frontal e hipocampo. A expressão do Pmch não se alterou após PS, RB ou RS em ZT8 nem em ZT0. Porém, houve diferenças na expressão do receptor Mchr1 no córtex frontal e no hipotálamo em ZT0. No córtex frontal, houve uma diminuição nos níveis de expressão nos grupos PS 96 e PS 120 comparados ao controle e no hipocampo houve um aumento nos grupos RB 96 e RS comparados ao PS 96. Ao comparar os níveis de expressão gênica entre ZT0 e ZT8, observamos que a expressão do Pmch não difere entre esses dois ZTs no grupo CT, porém há um aumento em ZT8, em comparação a ZT0 nos grupos PS (96 e 120) e RB (96 e 120). Quanto ao Mchr1, há aumento em ZT8 em comparação a ZT0 nos grupos CT, RB (96 e 120) e RS. Nós concluímos que os níveis de MCH no líquor são regulados tanto por um fator circadiano, quanto pelo ciclo sono/vigília Em relação à expressão gênica, a expressão do Pmch não se alterou nos dois ZTs analisados, entretanto, a expressão gênica do Mchr1 foi alterada apenas em ZT0, e teve uma diminuição nos grupos privados de sono, com inatividade desses neurônios durante a vigília. Esses resultados demonstram que o sistema MCHérgico é controlado pelo ciclo sono/vigília e que quando o sono é perturbado, o sistema MCHérgico responde diferencialmente em dois momentos do dia.
Within the hypothalamus there are neurons that utilize melanin concentrating hormone (MCH) as neuromodulators. These neurons project throughout the central nervous system and have important physiological functions; several experimental studies have suggested that MCH promotes sleep. So the objective of this study was investigate the effects of sleep deprivation, rebound and sleep restriction on the MCHergic system in twoo moments of the ligth-dark cycle (ZT0 and ZT8). For this we quantified the level of MCH in the cerebrospinal fluid (CSF) in rats after paradoxical sleep deprivation (SD), rebound (RB) and sleep restriction (SR) during subjective day (Zeitgeber time - ZT8, period of greater amount of sleep) and at the end of the subjective night (ZT0, time when the lights of the experimental room turn on). In the control condition (CT - waking and sleep ad libitum), there was no difference in the CSF MCH levels between ZT8 and. However, when sleep was disturbed, a significant difference was observed. Furthermore, when CSF was collected at ZT0, the MCH levels significantly increased in the RB 96 group compared to CT. When CSF collections were performed at ZT8, the SR group presented significantly increased levels of MCH compared to CT, SD 96 and SD 120.In order to know the dynamic relationship between MCH levels in the CSF (circulating protein) and its gene expression in the brain, we also investigated the MCH precursor (Pmch) expression in the hypothalamus and the receptor 1 (Mchr1) in the frontal cortex and hippocampus. The Pmch did not change after SD, RB or SR neither in ZT8 nor in ZT0. However, there were differences in the receptor Mchr1 expression in the frontal cortex and in the hypotalamus in ZT0. In the frontal cortex, there was a reduction of the expression levels in the SD 96 and SD 120 group compared to the CT and in the hippocampus there was an increase in the RB 96 and SR groups compared to SD 96. When we compared the gene expression levels between ZT0 and ZT8, we observed that Pmch expression did not differ between these two ZTs in the CT group, however, there was an increase in ZT8 compared to ZT0 in the SD (96 and 120) and RB (96 and 120). Considering the Mchr1, there was an increase in ZT8 compared to ZT0 in the CT, RB (96 and 120) and SR. We concluded that the MCH levels in the CSF are regulated by both a circadian factor and by the sleep-waking cycle Concerning gene expression, Pmch expression did not changed in the two ZTs analyzed, however, Mchr1 expression was altered only in ZT0, and has a decrease in SD groups in tandem with the inactivity of these neurons during wakefulness.
Within the hypothalamus there are neurons that utilize melanin concentrating hormone (MCH) as neuromodulators. These neurons project throughout the central nervous system and have important physiological functions; several experimental studies have suggested that MCH promotes sleep. So the objective of this study was investigate the effects of sleep deprivation, rebound and sleep restriction on the MCHergic system in twoo moments of the ligth-dark cycle (ZT0 and ZT8). For this we quantified the level of MCH in the cerebrospinal fluid (CSF) in rats after paradoxical sleep deprivation (SD), rebound (RB) and sleep restriction (SR) during subjective day (Zeitgeber time - ZT8, period of greater amount of sleep) and at the end of the subjective night (ZT0, time when the lights of the experimental room turn on). In the control condition (CT - waking and sleep ad libitum), there was no difference in the CSF MCH levels between ZT8 and. However, when sleep was disturbed, a significant difference was observed. Furthermore, when CSF was collected at ZT0, the MCH levels significantly increased in the RB 96 group compared to CT. When CSF collections were performed at ZT8, the SR group presented significantly increased levels of MCH compared to CT, SD 96 and SD 120.In order to know the dynamic relationship between MCH levels in the CSF (circulating protein) and its gene expression in the brain, we also investigated the MCH precursor (Pmch) expression in the hypothalamus and the receptor 1 (Mchr1) in the frontal cortex and hippocampus. The Pmch did not change after SD, RB or SR neither in ZT8 nor in ZT0. However, there were differences in the receptor Mchr1 expression in the frontal cortex and in the hypotalamus in ZT0. In the frontal cortex, there was a reduction of the expression levels in the SD 96 and SD 120 group compared to the CT and in the hippocampus there was an increase in the RB 96 and SR groups compared to SD 96. When we compared the gene expression levels between ZT0 and ZT8, we observed that Pmch expression did not differ between these two ZTs in the CT group, however, there was an increase in ZT8 compared to ZT0 in the SD (96 and 120) and RB (96 and 120). Considering the Mchr1, there was an increase in ZT8 compared to ZT0 in the CT, RB (96 and 120) and SR. We concluded that the MCH levels in the CSF are regulated by both a circadian factor and by the sleep-waking cycle Concerning gene expression, Pmch expression did not changed in the two ZTs analyzed, however, Mchr1 expression was altered only in ZT0, and has a decrease in SD groups in tandem with the inactivity of these neurons during wakefulness.
Descrição
Citação
AGAMME, Ana Luiza Dias Abdo. Respostas do sistema MCHérgico à privação e restrição de sono em ratos. 2014. 67 f. Dissertação (Mestrado) - Escola Paulista de Medicina, Universidade Federal de São Paulo (UNIFESP), São Paulo, 2014.