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(Referência obtida automaticamente do Web of Science, por meio da informação sobre o financiamento pela FAPESP e o número do processo correspondente, incluída na publicação pelos autores.)

Sympathetic-mediated hypertension of awake juvenile rats submitted to chronic intermittent hypoxia is not linked to baroreflex dysfunction

Texto completo
Autor(es):
Zoccal, Daniel B. [1] ; Bonagamba, Leni G. H. [1] ; Paton, Julian F. R. [2] ; Machado, Benedito H. [1]
Número total de Autores: 4
Afiliação do(s) autor(es):
[1] Univ Sao Paulo, Sch Med, Dept Physiol, BR-14049900 Ribeirao Preto, SP - Brazil
[2] Univ Bristol, Sch Med Sci, Bristol Heart Inst, Dept Physiol & Pharmacol, Bristol BS8 1TD, Avon - England
Número total de Afiliações: 2
Tipo de documento: Artigo Científico
Fonte: Experimental Physiology; v. 94, n. 9, p. 972-983, SEP 1 2009.
Citações Web of Science: 71
Resumo

In the present study, we evaluated the mechanisms underpinning the hypertension observed in freely moving juvenile rats submitted to chronic intermittent hypoxia (CIH). Male juvenile Wistar rats (20-21 days old) were submitted to CIH (6% O(2) for 40 s every 9 min, 8 h day(-1)) for 10 days while control rats were maintained in normoxia. Prior to CIH, baseline systolic arterial pressure (SAP), measured indirectly, was similar between groups (86 +/- 1 versus 87 +/- 1 mmHg). After exposure to CIH, SAP recorded directly was higher in the CIH (n = 28) than in the control group (n = 29; 131 +/- 3 versus 115 +/- 2 mmHg, P < 0.05). This higher SAP of CIH rats presented an augmented power of oscillatory components at low (10.05 +/- 0.91 versus 5.02 +/- 0.63 mmHg(2), P < 0.05) and high (respiratory-related) frequencies (12.42 +/- 2.46 versus 3.28 +/- 0.61 mmHg(2), P < 0.05) in comparison with control animals. In addition, rats exposed to CIH also exhibited an increased cardiac baroreflex gain (-3.11 +/- 0.08 versus -2.1 +/- 0.10 beats min(-1) mmHg(-1), P < 0.0001), associated with a shift to the right of the operating point, in comparison with control rats. Administration of hexamethonium (ganglionic blocker, i.v.), injected after losartan (angiotensin II type 1 receptor antagonist) and {[}beta-mercapto-beta,beta-cyclopenta-methylenepropionyl(1), O-Me-Tyr(2), Arg(8)]-vasopressin (vasopressin type 1a receptor antagonist), produced a larger depressor response in the CIH (n = 8) than in the control group (n = 9; -49 +/- 2 versus -39 +/- 2 mmHg, P < 0.05). Fifteen days after the cessation of exposure to CIH, the mean arterial pressure of CIH rats returned to normal levels. The data indicate that the sympathetic-mediated hypertension observed in conscious juvenile rats exposed to CIH is not secondary to a reduction in cardiac baroreflex gain and exhibits a higher respiratory modulation, indicating that an enhanced respiratory-sympathetic coupling seems to be the major factor contributing to hypertension in rats exposed to CIH. (AU)

Processo FAPESP: 04/03285-7 - Mecanismos centrais da excitação simpática promovida pela hipóxia
Beneficiário:Benedito Honorio Machado
Linha de fomento: Auxílio à Pesquisa - Temático
Processo FAPESP: 06/51159-6 - Aspectos da neurotransmissão glutamatérgica e purinérgica no núcleo do trato solitário de ratos jovens submetidos à hipóxia intermitente
Beneficiário:Daniel Breseghello Zoccal
Linha de fomento: Bolsas no Brasil - Doutorado