Lauand F, Ruginsk S G, Rodrigues H L P, Reis W L, de Castro M, Elias L L K, Antunes-Rodrigues J
Department of Physiology, School of Medicine of Ribeirao Preto, University of Sao Paulo, Avenida dos Bandeirantes, 3900 Monte Alegre, CEP 14049-900 Ribeirao Preto, SP, Brazil.
Neuroscience. 2007 Jun 15;147(1):247-57. doi: 10.1016/j.neuroscience.2007.04.021. Epub 2007 May 23.
The regulation of fluid and electrolyte homeostasis involves the participation of several neuropeptides and hormones that utilize hypothalamic cholinergic, alpha-adrenergic and angiotensinergic neurotransmitters and pathways. Additionally, it has been suggested that hypothalamus-pituitary-adrenal axis activity modulates hormonal responses to blood volume expansion. In the present study, we evaluated the effect of dexamethasone on atrial natriuretic peptide (ANP), oxytocin (OT) and vasopressin (AVP) responses to i.c.v. microinjections of 0.15 M and 0.30 M NaCl, angiotensin-II (ANG-II) and carbachol. We also evaluated the Fos protein immunoreactivity in the median preoptic (MnPO), paraventricular (PVN) and supraoptic (SON) nuclei. Male Wistar rats received an i.p. injection of dexamethasone (1 mg/kg) or vehicle (0.15 M NaCl) 2 h before the i.c.v. microinjections. Blood samples for plasma ANP, OT, AVP and corticosterone determinations were collected at 5 and 20 min after stimulus. Another set of rats was perfused 120 min after stimulation. A significant increase in plasma ANP, OT, AVP and corticosterone levels was observed at 5 and 20 min after each central stimulation compared with isotonic saline-injected group. Pre-treatment with dexamethasone decreased plasma corticosterone and OT levels, with no changes in the AVP secretion. On the other hand, dexamethasone induced a significant increase in plasma ANP levels. A significant increase in the number of Fos immunoreactive neurons was observed in the MnPO, PVN and SON after i.c.v. stimulations. Pre-treatment with dexamethasone induced a significant decrease in Fos immunoreactivity in these nuclei compared with the vehicle. These results indicate that central osmotic, cholinergic, and angiotensinergic stimuli activate MnPO, PVN and SON, with a subsequent OT, AVP, and ANP release. The present data also suggest that these responses are modulated by glucocorticoids.
体液和电解质平衡的调节涉及多种神经肽和激素的参与，这些神经肽和激素利用下丘脑胆碱能、α-肾上腺素能和血管紧张素能神经递质及信号通路。此外，有研究表明下丘脑-垂体-肾上腺轴的活动可调节机体对血容量增加的激素反应。在本研究中，我们评估了地塞米松对心房利钠肽（ANP）、催产素（OT）和血管加压素（AVP）对脑室内注射0.15 M和0.30 M氯化钠、血管紧张素II（ANG-II）和卡巴胆碱的反应的影响。我们还评估了视前正中核（MnPO）、室旁核（PVN）和视上核（SON）中Fos蛋白的免疫反应性。雄性Wistar大鼠在脑室内微量注射前2小时腹腔注射地塞米松（1 mg/kg）或溶剂（0.15 M氯化钠）。在刺激后5分钟和20分钟采集血样，用于测定血浆ANP、OT、AVP和皮质酮水平。另一组大鼠在刺激后120分钟进行灌注。与注射等渗盐水的组相比，每次中枢刺激后5分钟和20分钟时，血浆ANP、OT、AVP和皮质酮水平均显著升高。地塞米松预处理可降低血浆皮质酮和OT水平，而AVP分泌无变化。另一方面，地塞米松可使血浆ANP水平显著升高。脑室内刺激后，MnPO、PVN和SON中Fos免疫反应性神经元数量显著增加。与溶剂组相比，地塞米松预处理可使这些核团中的Fos免疫反应性显著降低。这些结果表明，中枢渗透压、胆碱能和血管紧张素能刺激可激活MnPO、PVN和SON，随后释放OT、AVP和ANP。目前的数据还表明，这些反应受糖皮质激素的调节。
