We have shown that intracellular superoxide (O(2)(*-)) production in CNS neurons 
plays a key role in the pressor, bradycardic, and dipsogenic actions of Ang II 
in the brain. In this study, we tested the hypothesis that a Rac1-dependent 
NADPH oxidase is a key source of O(2)(*-) in Ang II-sensitive neurons and is 
involved in these central Ang II-dependent effects. We performed both in vitro 
and in vivo studies using adenoviral (Ad)-mediated expression of 
dominant-negative Rac1 (AdN17Rac1) to inhibit Ang II-stimulated Rac1 activation, 
an obligatory step in NADPH oxidase activation. Ang II induced a time-dependent 
increase in Rac1 activation and O(2)(*-) production in Neuro-2A cells, and this 
was abolished by pretreatment with AdN17Rac1 or the NADPH oxidase inhibitors 
apocynin or diphenylene iodonium. AdN17Rac1 also inhibited Ang II-induced 
increases in NADPH oxidase activity in primary neurons cultured from central 
cardiovascular control regions. In contrast, overexpression of wild-type Rac1 
(AdwtRac1) caused more robust NADPH oxidase-dependent O(2)(*-) production to Ang 
II. To extend the in vitro studies, the pressor, bradycardic, and drinking 
responses to intracerebroventricularly (ICV) injected Ang II were measured in 
mice that had undergone gene transfer of AdN17Rac1 or AdwtRac1 to the brain. 
AdN17Rac1 abolished the increase in blood pressure, decrease in heart rate, and 
drinking response induced by ICV injection of Ang II, whereas AdwtRac1 enhanced 
these physiological effects. The exaggerated physiological responses in 
AdwtRac1-treated mice were abolished by O(2)(*-) scavenging. These results, for 
the first time, identify a Rac1-dependent NADPH oxidase as the source of central 
Ang II-induced O(2)(*-) production, and implicate this oxidase in cardiovascular 
diseases associated with dysregulation of brain Ang II signaling, including 
hypertension.