Effects of ouabain on neuronal thermosensitivity in hypothalamic tissue slices.
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.
Curras
M C
MC
Department of Physiology, College of Medicine, Ohio State University, Columbus 43210.
Boulant
J A
JA
D000818:Animals; D001833:Body Temperature Regulation / Q000187:drug effects*; D002118:Calcium / Q000378:metabolism; D007031:Hypothalamus / Q000187:drug effects / Q000502:physiology*; D066298:In Vitro Techniques; D008274:Magnesium / Q000494:pharmacology; D008297:Male; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D010042:Ouabain / Q000494:pharmacology*; D011188:Potassium / Q000378:metabolism; D051381:Rats; D011919:Rats, Inbred Strains; D012964:Sodium / Q000378:metabolism
D010042:Ouabain; D012964:Sodium; D008274:Magnesium; D011188:Potassium; D002118:Calcium