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1 School of Medicine of Ribeirao Preto - USP
2 School of Medicine of Ribeirão Preto
3 University of Sao Paulo, School of Medicine of Ribeirao Preto
4 School of Medicine of Ribeirao Preto
* To whom correspondence should be addressed. E-mail: hcsalgad{at}fmrp.usp.br.
The role played by the sympathetic drive in the development of L-NAME - induced hypertension is not firmly established. Therefore, the current study was undertaken in conscious rats in which hypertension was induced by treatment with L-NAME over the course of either two or fourteen days. Mean arterial pressure (MAP) was measured via a catheter placed in the femoral artery, drugs were administered via a cannula placed in the femoral vein, and renal sympathetic nerve activity (RSNA) was monitored using an implanted electrode. Despite the remarkable increase in arterial pressure, heart rate did not change after treatment with L-NAME. RSNA was similar in L-NAME-induced hypertensive rats treated over the course of two days or fourteen days, as well as in normotensive rats. It was also demonstrated that L-NAME-induced hypertensive rats displayed a resetting of the baroreflex control of RSNA to hypertensive levels, with decreased sensitivity over the course of two or fourteen days. Furthermore, the sympathetic-vagal balance examined in the time and frequency domain and the renal and plasma norepinephrine content did not differ between groups. In conclusion, the evaluation of the sympathetic drive in conscious rats demonstrated that the arterial hypertension induced by L-NAME treatment over the course of two and fourteen days does not show sympathetic overactivity.
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