Navegando por Palavras-chave "chemoreceptor"

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    Antihypertensive effects of central ablations in spontaneously hypertensive rats
    (Amer Physiological Soc, 2009-06-01) Moreira, Thiago S.; Takakura, Ana C. [UNIFESP]; Colombari, Eduardo [UNIFESP]; Menani, Jose V.; Universidade de São Paulo (USP); Universidade Federal de São Paulo (UNIFESP); UNESP
    Moreira TS, Takakura AC, Colombari E, Menani JV. Antihypertensive effects of central ablations in spontaneously hypertensive rats. Am J Physiol Regul Integr Comp Physiol 296: R1797-R1806, 2009. First published April 1, 2009; doi:10.1152/ajpregu.90730.2008.-Commissural nucleus of the solitary tract (commNTS) lesions transitorily (first 5 days) reduce mean arterial pressure (MAP) in spontaneously hypertensive rats (SHR), and lesions of the tissue surrounding the anteroventral third ventricle (AV3V region) chronically reduce MAP in other models of hypertension. in the present study, we investigated the effects of combined AV3V+commNTS electrolytic lesions on MAP and heart rate (HR) in conscious SHR. Baseline MAP and HR were recorded in male SHR before and for the next 40 days after sham or AV3V lesions combined with sham or commNTS lesions. the AV3V lesions produced no change in MAP in SHR, while commNTS lesions reduced MAP acutely (121 +/- 2 to 127 +/- 3 mmHg in the 1st and 5th days, respectively, vs. prelesion: 192 4 mmHg) but not chronically (from 10 to 40 days). However, combined AV3V+commNTS lesions reduced MAP of SHR chronically (119 +/- 2 to 161 +/- 4 mmHg, in the 1st and 40th day, respectively, vs. prelesion levels: 186 +/- 4 mmHg) or sham-lesioned SHR (187 +/- 4 to 191 +/- 6 mmHg). Sympathetic and angiotensinergic blockade produced less reduction in MAP in SHR with AV3V+commNTS-lesions, and there was no relationship between changes on water and food intake, body weight, or urinary excretion produced by AV3V+commNTS lesions with the changes in MAP. the present findings suggest that in the absence of the commNTS, the AV3V region contributes to the hypertension observed in SHR by mechanisms that appear to involve enhanced angiotensinergic and sympathetic activity.
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    Cardiovascular responses to microinjection of L-glutamate into the NTS in AV3V-lesioned rats
    (Elsevier B.V., 2004-10-29) Vieira, A. A.; Colombari, E.; De Luca, L. A.; Colombari, DSD; Menani, J. V.; UNESP; Universidade Federal de São Paulo (UNIFESP)
    The excitatory amino acid L-glutamate injected into the nucleus of the solitary tract (NTS) in unanesthetized rats similar to peripheral chemoreceptor activation increases mean arterial pressure (MAP) and reduces heart rate. in this study, we investigated the effects of acute (I day) and chronic (15 days) electrolytic lesions of the preoptic-periventricular tissue surrounding the anteroventral third ventricle (AV3V region) on the pressor and bradycardic responses induced by injections of L-glutamate into the NTS or peripheral chemoreceptor activation in unanesthetized rats. Male Holtzman rats with sham or electrolytic AV3V lesions and a stainless steel cannula implanted into the NTS were used. Differently from the pressor responses (28 +/- 3 mm Hg) produced by injections into the NTS of sham-lesioned rats, L-glutamate (5 nmol/ 100 nl) injected into the NTS reduced MAP (-26 +/- 8 mm Hg) or produced no effect (2 7 turn Hg) in acute and chronic AV3V-lesioned rats, respectively. the bradycardia to L-glutamate into the NTS and the cardiovascular responses to chemoreflex activation with intravenous potassium cyanide or to baroreflex activation with intravenous phenylephrine or sodium nitroprusside were not modified by AV3V lesions. the results show that the integrity of the AV3V region is essential for the pressor responses to L-glutamate into the NTS but not for the pressor responses to chemoreflex activation, suggesting dissociation between the central mechanisms involved in these responses. (C) 2004 Elsevier B.V. All rights reserved.
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    Enhanced pressor response to carotid occlusion in commNTS-lesioned rats: possible efferent mechanisms
    (Amer Physiological Soc, 2000-05-01) Sato, Monica Akemi [UNIFESP]; Menani, Jose Vanderlei; Lopes, Oswaldo Ubriaco [UNIFESP]; Colombari, Eduardo [UNIFESP]; Universidade Federal de São Paulo (UNIFESP); Univ Estadual Paulista
    Bilateral common carotid occlusion (BCO) over a period of 60 s in conscious rats produces a biphasic presser response, consisting of an early (peak) and late (plateau) phase. In this study we investigated 1) the effects of lesions of the commissural nucleus of the solitary tract (commNTS) on the cardiovascular responses produced by BCO in conscious rats and 2) the autonomic and humoral mechanisms activated to produce the presser response to BCO in sham- and commNTS-lesioned rats. Both the peak and plateau of the presser response produced by BCO increased in commNTS-lesioned rats despite the impairment of chemoreflex responses induced by intravenous potassium cyanide. In sham rats sympathetic blockade with intravenous prazosin and metoprolol, but not vasopressin receptor blockade with the Manning compound, reduced both components of BCO. In commNTS-lesioned rats the sympathetic blockade or vasopressin receptor blockade reduced both components of BCO. The results showed 1) the sympathetic nervous system, but not vasopressin, is important for the presser response to BCO during 60 s in conscious sham rats; 2) in commNTS-lesioned rats, despite chemoreflex impairment, BCO produces an increased presser response dependent on sympathetic activity associated with vasopressin release; and 3) the increment in the presser response to BCO in commNTS-lesioned rats seems to depend only on vasopressin secretion.