Sympathetic activation in rats with L-NAME-induced hypertension

Abstract

We evaluated the hemodynamic pattern and the contribution of the sympathetic nervous system in conscious and anesthetized (1.4 g/kg urethane, iv) Wistar rats with L-NAME-induced hypertension (20 mg/ kg daily). The basal hemodynamic profile was similar for hypertensive animals, conscious (N = 12) or anesthetized (N = 12) treated with L-NAME for 2 or 7 days: increase of total peripheral resistance associated with a decrease of cardiac output (CO) compared to normotensive animals, conscious (N = 14) or anesthetized (N = 14). Sympathetic blockade with hexamethonium essentially caused a decrease in total peripheral resistance in hypertensive animals (conscious, 2 days: from (means ± SEM) 2.47 ± 0.08 to 2.14 ± 0.07; conscious, 7 days: from 2.85 ± 0.13 to 2.07 ± 0.33; anesthetized, 2 days: from 3.00 ± 0.09 to 1.83 ± 0.25 and anesthetized, 7 days: from 3.56 ± 0.11 to 1.53 ± 0.10 mmHg mL -1 min -1 ) with no change in CO in either group. However, in the normotensive group a fall in CO (conscious: from 125 ± 4.5 to 96 ± 4; anesthetized: from 118 ± 1.5 to 104 ± 5.5 mL/min) was observed. The responses after hexamethonium were more prominent in the hypertensive anesthetized group. However, no difference was observed between conscious and anesthetized normotensive rats in response to sympathetic blockade. The present study shows that the vasoconstriction in response to L-NAME was mediated by the sympathetic drive. The sympathetic tone plays an important role in the initiation and maintenance of hypertension.

Brain, Heart and Kidney Correlate for the Control of Blood Pressure and Water Balance: Role of Angiotensinases

“…3), the correlations between HT and VT were similar in control, L -NAME- or propranolol-treated groups, with no clear positive or negative influence in both locations. This fits with the suggestion that the L -NAME-induced increase in blood pressure is mainly due to an increased peripheral resistance and not to an increased volume output [37]. In the kidney, L -NAME induced a positive correlation mainly between HT and RC, which also suggests an increased sympathetic activation, therefore leading to an increased renin secretion and thus contributing to the increase in peripheral resistance.…”

Effects of Gmelina arborea, Roxb (Verbenaceae) aqueous extract on arterial pressure of Wistar rats

“…Although in rats, many authors have used administration of doses higher than 20 mg/kg/day (Santos de Araujo et al, 2013;Sung et al, 2013), in this study, 7-days treatment of rats at this dose was sufficient to induce a significant increase in blood pressure. These data are in agreement with those of Biancardi where significant increase of blood pressure was observed after 2 and 7 days L-NAME administration (Biancardi et al, 2007). Moreover the increased pressure induced by L-NAME in the present work was enough higher for at least 7additional days from the end of the hypertension induction protocol when compared with control group.…”

Effects of aerobic exercise training in animal models of hypertension.

“…(68) The direct effect of L-NAME preventing endothelial synthesis of NO and reducing the tonic vasodilation is an important mechanism in the genesis of this model experimental hypertension. (69) The pressure in this experimental model was also associated with kidney damage, characterized by glomerulosclerosis, glomerular ischemia and renal interstitial infiltrate. (65,66) Studies from our group showed that 10 weeks of APT mildmoderate intensity treadmill in hypertensive rats by L-NAME administration did not induce reduction in BP.…”

“…(65,66) Studies from our group showed that 10 weeks of APT mildmoderate intensity treadmill in hypertensive rats by L-NAME administration did not induce reduction in BP. (70) However, an improvement of peripheral insulin sensitivity occurred (69) and reduction of blood pressure levels (unpublished data) after a training session in the L-NAME trained animals compared to the sedentary group.…”