AGT and Hypernatremia: Similar to the OVLT, the SFO is the main brain region where ANG II affects cardiovascular function, and electrophysiological recordings have shown that ANG II injection or plasma hypernatremia increases the firing rate of half of the SFO neurons and that electrical stimulation of the SFO leads to an increase in blood pressure via sympathetic pathways (Ferguson and Renaud, 1984; Gutman et al., 1988).