Approximate locations of the PVN neurons. Top: △, units antidromically activated from the RVLM only; ▲, units activated by ARN stimulation and by RVLM stimulation. Bottom: ○, units not antidromically activated from the RVLM; ●, units activated by ARN stimulation but not by RVLM stimulation. The distance (in mm) posterior to bregma is shown for each section. AH, anterior hypothalamic nucleus; f, fornix; 3V, 3rd ventricle; OX, optic tract; SO, supraoptic nucleus.