Navegando por Palavras-chave "RVLM"

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    Asymmetrical changes in lumbar sympathetic nerve activity following stimulation of the sciatic nerve in rat
    (Elsevier B.V., 2011-05-19) Korim, Willian Seiji; McMullan, Simon; Cravo, Sergio L. [UNIFESP]; Pilowsky, Paul M.; Macquarie Univ; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP)
    Noxious stimulation of the leg increases hind limb blood flow (HBF) to the ipsilateral side and decreases to the contralateral in rat. Whether or not this asymmetrical response is due to direct control by sympathetic terminals or mediated by other factors such as local metabolism and hormones remains unclear. the aim of this study was to compare responses in lumbar sympathetic nerve activity, evoked by stimulation of the ipsilateral and contralateral sciatic nerve (SN). We also sought to determine the supraspinal mechanisms involved in the observed responses. in anesthetized and paralyzed rats, intermittent electrical stimulation (1 mA, 0.5 Hz) of the contralateral SN evoked a biphasic sympathoexcitation. Following ipsilateral SN stimulation, the response is preceded by an inhibitory potential with a latency of 50 ms (N=26). Both excitatory and inhibitory potentials are abolished following cervical Cl spinal transection (N=6) or bilateral microinjections of muscimol (N=6) in the rostral ventrolateral medulla (RVLM). This evidence is suggestive that both sympathetic potentials are supraspinally mediated in this nucleus. Blockade of RVLM glutamate receptors by microinjection of kynurenic acid (N=4) selectively abolished the excitatory potential elicited by ipsilateral SN stimulation. This study supports the physiological model that activation of hind limb nociceptors evokes a generalized sympathoexcitation, with the exception of the ipsilateral side where there is a withdrawal of sympathetic tone resulting in an increase in HBF. Crown Copyright (C) 2011 Published by Elsevier B.V. All rights reserved.
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    Cardiovascular responses to microinjections of GABA or anesthetics into the rostral ventrolateral medulla of conscious and anesthetized rats
    (Associação Brasileira de Divulgação Científica, 2003-09-01) Lacerda, J.e.c. [UNIFESP]; Campos, Ruy Ribeiro [UNIFESP]; Araujo, G.c. [UNIFESP]; Andreatta-van Leyen, S. [UNIFESP]; Lopes, Oswaldo Ubriaco [UNIFESP]; Guertzenstein, P.g. [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    The rostral ventrolateral medulla (RVLM) contains neurons involved in tonic and reflex control of arterial pressure. We describe the effects of gamma-aminobutyric acid (GABA) and anesthetics injected into the RVLM of conscious and urethane (1.2 g/kg, iv) anesthetized Wistar rats (300-350 g). In conscious rats, bilateral microinjection of GABA (50 nmol/200 nl) induced a small but significant decrease in blood pressure (from 130 ± 3.6 to 110 ± 5.6 mmHg, N = 7). A similar response was observed with sodium pentobarbital microinjection (24 nmol/200 nl). However, in the same animals, the fall in blood pressure induced by GABA (from 121 ± 8.9 to 76 ± 8.8 mmHg, N = 7) or pentobarbital (from 118 ± 4.5 to 57 ± 11.3 mmHg, N = 6) was significantly increased after urethane anesthesia. In contrast, there was no difference between conscious (from 117 ± 4.1 to 92 ± 5.9 mmHg, N = 7) and anesthetized rats (from 123 ± 6.9 to 87 ± 8.7 mmHg, N = 7) when lidocaine (34 nmol/200 nl) was microinjected into the RVLM. The heart rate variations were not consistent and only eventually reached significance in conscious or anesthetized rats. The right position of pipettes was confirmed by histology and glutamate microinjection into the RVLM. These findings suggest that in conscious animals the RVLM, in association with the other sympathetic premotor neurons, is responsible for the maintenance of sympathetic vasomotor tone during bilateral RVLM inhibition. Activity of one or more of these premotor neurons outside the RVLM can compensate for the effects of RVLM inhibition. In addition, the effects of lidocaine suggest that fibers passing through the RVLM are involved in the maintenance of blood pressure in conscious animals during RVLM inhibition.
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    Interaction of medullary P2 and glutamate receptors mediates the vasodilation in the hindlimb of rat
    (Springer, 2012-12-01) Korim, Willian Seiji [UNIFESP]; Ferreira-Neto, Marcos L.; Pedrino, Gustavo R.; Pilowsky, Paul M.; Cravo, Sergio L. [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); Macquarie Univ; Universidade Federal de Uberlândia (UFU); Universidade Federal de Goiás (UFG)
    In the nucleus tractus solitarii (NTS) of rats, blockade of extracellular ATP breakdown to adenosine reduces arterial blood pressure (AP) increases that follow stimulation of the hypothalamic defense area (HDA). the effects of ATP on NTS P2 receptors, during stimulation of the HDA, are still unclear. the aim of this study was to determine whether activation of P2 receptors in the NTS mediates cardiovascular responses to HDA stimulation. Further investigation was taken to establish if changes in hindlimb vascular conductance (HVC) elicited by electrical stimulation of the HDA, or activation of P2 receptors in the NTS, are relayed in the rostral ventrolateral medulla (RVLM); and if those responses depend on glutamate release by ATP acting on presynaptic terminals. in anesthetized and paralyzed rats, electrical stimulation of the HDA increased AP and HVC. Blockade of P2 or glutamate receptors in the NTS, with bilateral microinjections of suramin (10 mM) or kynurenate (50 mM) reduced only the evoked increase in HVC by 75 % or more. Similar results were obtained with the blockade combining both antagonists. Blockade of P2 and glutamate receptors in the RVLM also reduced the increases in HVC to stimulation of the HDA by up to 75 %. Bilateral microinjections of kynurenate in the RVLM abolished changes in AP and HVC to injections of the P2 receptor agonist alpha,beta-methylene ATP (20 mM) into the NTS. the findings suggest that HDA-NTS-RVLM pathways in control of HVC are mediated by activation of P2 and glutamate receptors in the brainstem in alerting-defense reactions.
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    Losartan Reduces Oxidative Stress Within the Rostral Ventrolateral Medulla of Rats With Renovascular Hypertension
    (Oxford Univ Press, 2013-07-01) Nishi, Erika E. [UNIFESP]; Bergamaschi, Cassia T. [UNIFESP]; Oliveira-Sales, Elizabeth B. [UNIFESP]; Simon, Karin A. [UNIFESP]; Campos, Ruy R. [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    Previous studies showed that the microinjection of antioxidants or the overexpression of superoxide dismutase within the rostral ventrolateral medulla (RVLM) reduces hypertension and sympathoexcitation in the 2-kidney, 1-clip (2K-1C) model. in this study, we hypothesized that angiotensin II (ANG II) type 1 receptor (AT(1)R) is involved in the oxidative stress within the RVLM and contributes to cardiovascular dysfunction in renovascular hypertension.Losartan (30mg/kg/day, oral gavage) was administered for 7 consecutive days by week 5 after implantation of the clip (gap width 0.2mm). Mean arterial pressure, baroreflex, and renal sympathetic nerve activity (rSNA) were evaluated. Superoxide production was evaluated by dihydroethidium (DHE) staining within the RVLM and within a control area. Systemic oxidative stress was characterized by measurement of thiobarbituric acid reactive substances (TBARS) and total glutathione (tGSH) in the blood.AT(1)R blockade significantly (P < 0.05) reduced hypertension by approximately 20% (n 11) and sympathoexcitation to the kidneys by approximately 41% (n 6) in the 2K-1C rats. Losartan treatment increased the baroreflex sensitivity of rSNA to pressor (67%) and depressor (140%) stimuli in the 2K-1C rats. AT(1)R blockade caused a significant (66%) reduction in DHE staining within the RVLM but not within the control area, reduced plasma TBARS (from 1.60.1 to 1.00.1 nmol/ml), and increased tGSH (from 3.40.4 to 5.20.3 mol/g Hb) in the 2K-1C group only.Our findings suggest that the beneficial effects of ANG II blockade in renovascular hypertension are partly due to preferential reduction of oxidative stress in the RVLM.
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    Stimulation of renal afferent fibers leads to activation of catecholaminergic and non-catecholaminergic neurons in the medulla oblongata
    (Elsevier Science Bv, 2017) Nishi, Erika E.[UNIFESP]; Martins, Beatriz S.[UNIFESP]; Milanez, Maycon I. O.[UNIFESP]; Lopes, Nathalia R.[UNIFESP]; de Melo, Jose F., Jr.[UNIFESP]; Pontes, Roberto B.; Girardi, Adriana C.; Campos, Ruy R.[UNIFESP]; Bergamaschi, Cassia T.[UNIFESP]
    Presympathetic neurons in the rostral ventrolateral medulla (RVLM) including the adrenergic cell groups play a major role in the modulation of several reflexes required for the control of sympathetic vasomotor tone and blood pressure (BP). Moreover, sympathetic vasomotor drive to the kidneys influence natriuresis and diuresis by inhibiting the cAMP/PKA pathway and redistributing the Na+/H+ exchanger isoform 3 (NHE3) to the body of the microvilli in the proximal tubules. In this study we aimed to evaluate the effects of renal afferents stimulation on (1) the neurochemical phenotype of Fos expressing neurons in the medulla oblongata and (2) the level of abundance and phosphorylation of NHE3 in the renal cortex. We found that electrical stimulation of renal afferents increased heart rate and BP transiently and caused activation of tyrosine hydroxylase (TH)-containing neurons in the RVLM and non-TH neurons in the NTS. Additionally, activation of the inhibitory renorenal reflex over a 30-min period resulted in increased natriuresis and diuresis associated with increased phosphorylation of NHE3 at serine 552, a surrogate for reduced activity of this exchanger, in the contralateral kidney. This effect was not dependent of BP changes considering that no effects on natriuresis or diuresis were found in the ipsilateral-stimulated kidney. Therefore, our data show that renal afferents leads to activation of catecholaminergic and non-catecholaminergic neurons in the medulla oblongata. When renorenal reflex is induced, NHE3 exchanger activity appears to be decreased, resulting in decreased sodium and water reabsorption in the contralateral kidney. (C) 2017 Elsevier B.V. All rights reserved.
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    Upregulation of AT(1)R and iNOS in the Rostral Ventrolateral Medulla (RVLM) Is Essential for the Sympathetic Hyperactivity and Hypertension in the 2K-1C Wistar Rat Model
    (Nature Publishing Group, 2010-07-01) Oliveira-Sales, Elizabeth Barbosa de [UNIFESP]; Nishi, Erika Emy [UNIFESP]; Boim, Mirian Aparecida [UNIFESP]; Dolnikoff, Miriam Sterman [UNIFESP]; Bergamaschi, Cassia T. [UNIFESP]; Campos, Ruy R. [UNIFESP]; Universidade Federal de São Paulo (UNIFESP)
    BACKGROUNDWe hypothesized that upregulation of angiotensin type 1 receptor (AT, R) and inducible nitric oxide (NO) synthase (iNOS) within the rostral ventrolateral medulla (RVLM) could contribute to two-kidney, one-clip (2K-1C) hypertension.METHODSThe experiments were performed in male Wistar rats, 6 weeks after the renal surgery. the animals were divided into control (SHAM, n = 18) and hypertensive groups (2K-1C, n = 18). Bilateral tissue punches were taken from sections containing the RVLM to perform iNOS gene expression analyses by the real-time PCR technique, and AT(1)R and iNOS protein expression analyses by western blotting. in addition, we injected losartan (1 nmol), an AT(1)R antagonist, and aminoguanidine (250 pmol), an iNOS inhibitor, bilaterally into the RVLM to analyze the mean arterial pressure (MAP) and renal sympathetic nerve activity (rSNA).RESULTSiNOS mRNA expression levels were greater (P < 0.05) in the 2K-1C group compared to the SHAM group. Furthermore, the AT(1)R and iNOS protein expression were significantly increased in the RVLM of 2K-1C rats compared to SHAM rats. Injection of losartan into the RVLM reduced the MAP (11%) and rSNA (18%) only in the 2K-1C rats, whereas injection of aminoguanidine in the same region decreased the MAP (31%) and rSNA (34%) in hypertensive rats.CONCLUSIONSThe present study suggests that upregulation of AT(1)R and iNOS in the RVLM is important in the maintenance of high blood pressure and renal sympathetic activation in 2K-1C hypertension.