Sympathetic activity is not increased in L-NAME hypertensive rats.
The role played by the sympathetic drive in the development of N(G)-nitro-l-arginine methyl ester (l-NAME)-induced hypertension is not firmly established. Therefore, the present study was undertaken in conscious rats in which hypertension was induced by treatment with l-NAME over the course of either 2 or 14 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 2 or 14 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 2 or 14 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 2 and 14 days does not show sympathetic overactivity.
Dos Santos
Fernanda Machado
FM
Dept. of Physiology, School of Medicine of Ribeirão Preto, Univ. of São Paulo, Av. Bandeirantes, 3900, 14048-900 Ribeirão Preto-SP, Brazil.
Martins Dias
Daniel Penteado
DP
da Silva
Carlos Alberto Aguiar
CA
Fazan
Rubens
R
Salgado
Helio Cesar
HC
D000818:Animals; D017704:Baroreflex / Q000502:physiology; D001794:Blood Pressure / Q000502:physiology; D003243:Consciousness / Q000502:physiology; D004195:Disease Models, Animal; D004791:Enzyme Inhibitors / Q000009:adverse effects; D006339:Heart Rate / Q000502:physiology; D006973:Hypertension / Q000378:metabolism / Q000503:physiopathology*; D007668:Kidney / Q000294:innervation* / Q000378:metabolism; D008297:Male; D019331:NG-Nitroarginine Methyl Ester / Q000494:pharmacology*; D009638:Norepinephrine / Q000378:metabolism; D051381:Rats; D017208:Rats, Wistar; D013564:Sympathetic Nervous System / Q000503:physiopathology*; D013997:Time Factors
D004791:Enzyme Inhibitors; D019331:NG-Nitroarginine Methyl Ester; D009638:Norepinephrine