Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
10835134 | Nitric Oxide | 2012 | 8 Pages |
Abstract
Hypertension is associated to an increase in central oxidative stress and an attenuation of the baroreflex control of arterial pressure. The present study evaluated the effect of alterations in the levels of nitric oxide (NO) and superoxide anion in the caudal ventrolateral medulla (CVLM), a key area of the brainstem for the baroreflex control of arterial pressure, in renovascular hypertensive rats (2K1C). Baseline mean arterial pressure (MAP), heart rate (HR), and reflex bradycardia were evaluated 30Â days after renal artery occlusion in anesthetized (urethane, 1.2Â g/kg, i.p.) 2K1C or normotensive (SHAM) rats. The MAP, HR, and baroreflex control of HR were evaluated before and after CVLM microinjections of the non-selective NOS inhibitor l-NAME (10Â nmol), the NO precursor l-ARG (50Â nmol), or the antioxidant ascorbic acid, Vit C (10Â nmol). In both 2K1C and SHAM animals, CVLM microinjection of l-NAME produced a decrease in MAP, whereas l-ARG induced a significant increase in MAP. However, microinjection of Vit C into the CVLM produced a decrease in MAP and HR only in 2K1C and not in SHAM rats. Cardiovascular effects produced by microinjection of l-ARG into the CVLM were abolished by prior microinjection of l-NAME in the CVLM of 2K1C and SHAM rats. Microinjection of l-NAME into the CVLM increased the sensitivity of reflex bradycardia in 2K1C animals. In contrast, the CVLM microinjection of l-ARG reduced reflex bradycardia only in SHAM rats. Vit C in the CVLM did not change reflex bradycardia in either 2K1C or in SHAM rats. These results suggest that increased oxidative stress in the CVLM during hypertension contributes to the reduced baroreflex sensitivity and to maintain hypertension in the 2K1C model.
Keywords
NTSSNS2K1CPulse intervalCVLMVLMNOSRVLMROSrostral ventrolateral medullal-argininesuperoxide anionl-ArgCNSsympathetic nervous systemcentral nervous systemParasympathetic nervous systemShamShrHeart ratemean arterial pressureBlood pressurePVNventrolateral medullacaudal ventrolateral medullanormotensive ratsspontaneous hypertensive ratsmillisecondmapNitric oxidenitric oxide synthasenucleus of the solitary tractparaventricular nucleus of the hypothalamusVit CPNSReactive oxygen species
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Authors
Uberdan Guilherme Mendes de Castro, Graziele Galdino de Sousa, Raquel do Pilar Machado, Mauro César Isoldi, Marcelo Eustáquio Silva, Ana Paula Nadu, Luiz Eduardo Sousa, Robson Augusto Souza dos Santos, Maria José Campagnole-Santos,