Hypovolaemic and osmotic stimuli induce distinct patterns of c-Fos expression in the rat subfornical organ

Investigation of the effects of osmotic and hypovolaemic stimuli on the pattern of subfornical organ (SFO) c-fos expression yielded three distinct distributions of activated neurons. Hypertonic saline induced c-fos expression in peripheral SFO only. PEG/water induced c-fos in the central core of SFO and PEG/saline induced c-fos in both the central and peripheral regions. Isotonic saline failed to induce SFO c-fos expression. These results are consistent with the notion of functional segregation within the SFO.