AJP - Regulatory, Integrative and Comparative Physiology, Vol 258, Issue 1 175-R181, Copyright © 1990 by American Physiological Society
In vitro osmosensitive hypothalamic neurons from hypertensive and normotensive rats
K. A. Travis and J. A. Boulant
Department of Physiology, College of Medicine, Ohio State University, Columbus 43210.
Single-unit activity was recorded in hypothalamic tissue slices from
spontaneously hypertensive (SH) and normotensive Wistar-Kyoto (WKY) rats to
identify differences in neuronal osmosensitivity between these two strains.
Neurons were characterized according to location, firing rate, temperature
sensitivity, and response to hyposmotic (280 mosmol/kgH2O) and hyperosmotic
(320 mosmol/kgH2O) media. More than half of the thermosensitive neurons
were also osmosensitive. Three groups of osmosensitive neurons were
identified: 1) low-firing neurons excited by hyposmolality and inhibited by
hyperosmolality, 2) high-firing neurons excited by hyposmolality, and 3)
high-firing neurons excited by hyperosmolality. There were no differences
between strains in terms of the proportions of osmosensitive neurons.
Compared with WKY neurons, however, SH osmosensitive neurons displayed
reduced sensitivity to hyperosmotic media. Also, SH osmotically insensitive
neurons displayed lower spontaneous firing rates. These differences in
osmosensitivity and spontaneous activity may provide a neuronal basis to
explain some of the differences in water and sodium regulation observed in
hypertensive rats.
