AJP - Regulatory, Integrative and Comparative Physiology, Vol 257, Issue 1 21-R28, Copyright © 1989 by American Physiological Society
Effects of ouabain on neuronal thermosensitivity in hypothalamic tissue slices
M. C. Curras and J. A. Boulant
Department of Physiology, College of Medicine, Ohio State University, Columbus 43210.
To determine the role of the electrogenic Na+-K+ pump in neuronal
thermosensitivity, single-unit activity was recorded in rat hypothalamic
tissue slices before, during, and after perfusions containing 10(-5) or
10(-6) M ouabain, a specific pump inhibitor. Most neurons were recorded in
the preoptic-anterior hypothalamus. Some neurons were also tested with high
magnesium-low calcium perfusions to determine ouabain's effects on neuronal
activity during synaptic blockade. When the neurons were characterized
according to thermosensitivity, 24% were warm sensitive, 8% were cold
sensitive, and 68% were temperature insensitive. Ouabain increased the
firing rate of 60% of all neurons. Ouabain did not reduce the
thermosensitivity of cold-sensitive and warm-sensitive neurons; however,
temperature-insensitive neurons became more warm sensitive during ouabain
perfusion. This increase in warm sensitivity did not occur with ouabain
plus high Mg2+-low Ca2+ perfusion, suggesting that Ca2+ is important in
this response. These results indicate that the Na-K pump is not responsible
for the thermosensitivity of hypothalamic cold-sensitive or warm-sensitive
neurons; however, this pump may be actively employed by many neurons that
remain insensitive to temperature changes.
