RESUMO
Water deprivation (WD) induces changes in plasma volume and osmolality, which in turn activate several responses, including thirst, the activation of the renin-angiotensin system (RAS) and vasopressin (AVP) and oxytocin (OT) secretion. These systems seem to be influenced by oestradiol, as evidenced by the expression of its receptor in brain areas that control fluid balance. Thus, we investigated the effects of oestradiol treatment on behavioural and neuroendocrine changes of ovariectomized rats in response to WD. We observed that in response to WD, oestradiol treatment attenuated water intake, plasma osmolality and haematocrit but did not change urinary volume or osmolality. Moreover, oestradiol potentiated WD-induced AVP secretion, but did not alter the plasma OT or angiotensin II (Ang II) concentrations. Immunohistochemical data showed that oestradiol potentiated vasopressinergic neuronal activation in the lateral magnocellular PVN (PaLM) and supraoptic (SON) nuclei but did not induce further changes in Fos expression in the median preoptic nucleus (MnPO) or subfornical organ (SFO) or in oxytocinergic neuronal activation in the SON and PVN of WD rats. Regarding mRNA expression, oestradiol increased OT mRNA expression in the SON and PVN under basal conditions and after WD, but did not induce additional changes in the mRNA expression for AVP in the SON or PVN. It also did not affect the mRNA expression of RAS components in the PVN. In conclusion, our results show that oestradiol acts mainly on the vasopressinergic system in response to WD, potentiating vasopressinergic neuronal activation and AVP secretion without altering AVP mRNA expression.
Assuntos
Desidratação/fisiopatologia , Estradiol/uso terapêutico , Estrogênios/uso terapêutico , Neurônios/efeitos dos fármacos , Núcleo Hipotalâmico Paraventricular/efeitos dos fármacos , Núcleo Supraóptico/efeitos dos fármacos , Desequilíbrio Hidroeletrolítico/prevenção & controle , Animais , Arginina Vasopressina/agonistas , Arginina Vasopressina/análise , Arginina Vasopressina/metabolismo , Comportamento Animal/efeitos dos fármacos , Desidratação/terapia , Ingestão de Líquidos/efeitos dos fármacos , Terapia de Reposição de Estrogênios , Feminino , Hidratação , Regulação da Expressão Gênica/efeitos dos fármacos , Proteínas do Tecido Nervoso/genética , Proteínas do Tecido Nervoso/metabolismo , Neurônios/metabolismo , Neurônios/patologia , Ovariectomia/efeitos adversos , Núcleo Hipotalâmico Paraventricular/metabolismo , Núcleo Hipotalâmico Paraventricular/patologia , Área Pré-Óptica/efeitos dos fármacos , Área Pré-Óptica/metabolismo , Área Pré-Óptica/patologia , Ratos Wistar , Órgão Subfornical/efeitos dos fármacos , Órgão Subfornical/metabolismo , Órgão Subfornical/patologia , Núcleo Supraóptico/metabolismo , Núcleo Supraóptico/patologia , Núcleo Vestibular Lateral/efeitos dos fármacos , Núcleo Vestibular Lateral/metabolismo , Núcleo Vestibular Lateral/patologia , Desequilíbrio Hidroeletrolítico/sangue , Desequilíbrio Hidroeletrolítico/etiologia , Desequilíbrio Hidroeletrolítico/fisiopatologiaRESUMO
Our aim was to investigate the effect of central NOS inhibition on hypothalamic arginine vasopressin (AVP) gene expression, hormone release and on the cardiovascular response during experimental sepsis. Male Wistar rats were intracerebroventricularly injected with the non-selective NO synthase (NOS) inhibitor (L-NAME) or aminoguanidine, a selective inhibitor of the inducible isoform (iNOS). After 30 min, sepsis was induced by cecal ligation and puncture (CLP) causing an increase in heart rate (HR), as well as a reduction in median arterial pressure (MAP) and AVP expression ratio (AVP(R)), mainly in the supraoptic nucleus. AVP plasma levels (AVPp) increased in the early but not in the late phase of sepsis. L-NAME pretreatment increased MAP but did not change HR. It also resulted in an increase in AVPp at all time points, except 24h, when it returned to basal levels. AVP(R), however remained reduced in both nuclei. Aminoguanidine pretreatment resulted in increased MAP in the early phase and higher AVP(R) in the supraoptic, but not in the paraventricular nucleus, while AVPp remained elevated at all time points. We suggest that increased central NO production, mainly inducible NOS-derived, reduces AVP gene expression differentially in supraoptic and paraventricular nuclei, and that this may contribute to low AVP plasma levels and hypotension in the late phase of sepsis.