Prolonged NOS inhibition in the brain elevates blood pressure in normotensive rats

Systemic inhibition of nitric oxide synthase (NOS) evokes hypertension, which is enhanced by salt loading, partly via augmented sympathetic activity. We investigated whether inhibition of brain NOS elevates blood pressure (BP) in normotensive rats and, if so, whether the BP elevation is enhanced by salt loading. After a 2-wk low-salt (0.3%) diet, male Sprague-Dawley (SD) rats were divided into four groups. Groups 1 and2 received a chronic intracerebroventricular infusion of 0.5 mg ⋅ kg−1 ⋅ day−1ofN G-monomethyl-l-arginine (l-NMMA), andgroups 3 and4 were given artificial cerebrospinal fluid (aCSF). Groups 1 and3 were placed on a high-salt (8%) diet, whereas groups 2 and4 were on a low-salt diet. Onday 9or 10,group 1 showed significantly higher mean arterial pressure (MAP) in a conscious unrestrained state (129 ± 3 mmHg vs. 114 ± 3, 113 ± 1, and 108 ± 3 mmHg ingroups 2, 3, and 4, respectively,P < 0.05). On a high-salt diet, response of renal sympathetic nerve activity but not of BP to air-jet stress was sig...