Osmosensitive neurons in the rat's preoptic area: medial-lateral comparison.

For the first time, brain-recording data were brought to bear directly on the question of a critical osmosensitive zone in the lateral preoptic area as specifically delimited in the rat by Blass and Epstein, and in the rabbit by Peck and Novin. Our data clearly showed that this critical zone in the lateral preoptic area of the rat contains cells that are osmosensitive. Simultaneous recording from cell populations (a) inside the critical zone and (b) in a zone medial to it showed that the net acceleratory response to challenge for the former was much greater than it was for the latter. These findings constitute new evidence for the critical importance of the lateral preoptic area in cellular dehydration thirst.