Envolvimento do núcleo pré-óptico mediano na regulação autonômica e cardiovascular
Nenhuma Miniatura disponível
Data
2015-02-25
Autores
Título da Revista
ISSN da Revista
Título de Volume
Editor
Universidade Federal de Goiás
Resumo
Studies have demonstrated that neurons in the median pre-optic nucleus (MnPO) play a key role in the organization of cardiovascular responses induced by changes in circulating volume mostly through their projections to the paraventricular nucleus (PVN) of the hypothalamus. PVN in turn, projects to the rostroventrolateral medulla (RVLM) one of the main generators nucleus of vascular sympathetic, renal and cardiac activity. However, the autonomic response of blocked of the MnPO and central pathways and / or mechanisms involved in these responses remains unknown. The present study sought to determine the involvement of the MnPO in cardiovascular and autonomic regulation in Wistar (WT) and spontaneously hypertensive rats (SHR). For these, rats of the lineages WT (n = 6) and SHR (n = 6), weighing between 250 and 300g were anesthetized with urethane (1.2 g / kg, iv.) after induction with halothane (2% in O2 100%). The right femoral artery and vein were cannulated for recording of mean arterial pressure (MAP), and infusion of drugs, respectively. Heart rate (HR) was calculated as instantaneous frequency signal electrocardiogram (ECG). The animals were positioned in a stereotaxic apparatus, and instrumented for recording renal sympathetic nerve activity (RSNA). The nanoinjections of saline (NaCl; 150 mM), kynurenic acid (glutamate receptor antagonist; 50 mM) and muscimol (GABA agonist; 4 mM) were also performed. As expected, saline nanoinjections did not change the values of MAP (WT: 0.4 ± 0.2 mmHg; SHR: 0.2 ± 0.4 mmHg), HR (WT: 0.7 ± 0.9 bpm; SHR, 1.1 ± 1.4 bpm) and RSNA (WT: 0.4 ± 0.2%; SHR: 0.2 ± 1.3%). In WT (n=6) rats, the blockade of the MnPO with muscimol promoted fall in MAP (-17.0 ± 1.2 mmHg), bradycardia (-55,4 ± 12,3 bpm) and reduces in RSNA (-37.5 ± 3.9 %). The muscimol nanoinjections into the MnPO in SHR (n=6) promoted hypotension (-31.6 ± 5.0 mmHg), bradycardia (-18.3 ± 7.2 bpm), and renal sympathoinhibition (-54.4 ± 6.2 %). The changes in cardiovascular and autonomic parameters were evaluated in WT and SH rats submitted to sinoartic denervation. In normotensive rats, the inhibition of the MnPO by muscimol promoted decrease of MAP in innervated rats (n=6) and denervated (-19.4 ± 1.9 vs. 20.9 ± 4.3 mmHg, respectively; 3min; n=6), which was maintained throughout the experimental period (13.5 ± 2.0 vs. 22.5 ± 4.3 mmHg, 30 min). Also did not evidenced differences in RSNA in WT innervated (-23.0 ± 1.5%; 3min) and denervated (-21.0 ± 4.9%; 3min) rats. In denervated hypertensive rats (n=5), the blocked of MnPO resulted in progressive decrease in MAP (-31.1 ± 6.7, ± 9.7 and -38.7 ± 7.1 -44.7 mmHg, respectively 3, 15 and 30 min after MnPO blockade). The changes observed in the HR (-1.3 ± 3.3; -21.5 ± 12.6 and -24.9 ± 12.2 bpm, respectively 3, 15 and 30 min after MnPO blockade) and RSNA (-16.4 ± 8.8; -37.3 ± 10.1 and -45.1 ± 8.7%, respectively 3, 15 and 30 min after MnPO blockade) also followed this pattern of response. Finally to identify the involvement of glutamatergic neurotransmission in the MnPO on the cardiovascular and autonomic control, nanoinjections of kynurenic acid were performed in this nucleus. The glutamatergic blockade promoted decrease in MAP (WT: -18.2 ± 4.1 mmHg; SHR: -21.0 ± 2.5 mmHg), bradycardia (WT: -7.1 ± 1, 9 bpm; SHR: -9.0 ± 6.0 bpm) and renal simpathoinhibition (WT: -19.7 ± 2.4%; SHR: -24.7 ± 2.4%) in normotensive and hypertensive rats. In summary, the results obtained on this study demonstrated that acute blockade of MnPO reduces blood pressure (BP), confirming recent data that indicate that this nucleus participates of tonic control on BP. Our data suggest the involvement of MnPO the tonic regulation of sympathetic activity in WT and SHR. In addition, suggest the participation of this nucleus in increased sympathetic activity and consequent arterial blood pressure in SHR. The results demonstrated that aortic and carotid afferent participates in the modulation of autonomic and cardiovascular responses induced by blockade the MnPO in SHR. Furthermore, our data suggest that glutamatergic neurotransmission in the MnPO is important for the tonic regulation of BP, HR and RSNA thus, bringing new evidence that this nucleus participates of the autonomic and cardiovascular control.
Descrição
Palavras-chave
Citação
MORÃO, A. A. Envolvimento do núcleo pré-óptico mediano na regulação autonômica e cardiovascular. 2015. 66 f. Dissertação (Mestrado em Biologia) - Universidade Federal de Goiás, Goiânia, 2015.