Rapid eye movement sleep deprivation induces changes in the high-affinity binding of [ 3H]-ouabain to the rat cortical membranes

Abstract

Rapid eye movement sleep (REMS) suppresses seizures. On the other hand, REMS deprivation (REMSD) increases brain susceptibility to seizures. Sodium–postassium/ATPase is involved in the control of brain excitability. Ouabain, a cardiotonic glycoside, binds to a regulatory extracellular allosteric site in the sodium–potassium/ATPase inhibiting/stimulating its activity depending on its concentration. Endogenous ouabain-like substances exist in the brain; therefore, changes in the ouabain binding site may be involved in the increased brain excitability induced by REMSD. Adult, Wistar male rats were deprived of REMS for 96 hours by the flower-pot method (REMSD). A stress control group was kept in the same environment on a larger platform (LP). A third group of rats was kept in the same room in their home-cages (CONTROL). After REMSD all rats were sacrificed by decapitation and their cerebral cortex dissected. High-affinity [ 3H]-ouabain binding was carried out in cortical crude membrane preparation using 8 concentrations of [ 3H]-ouabain (1–24 nM). The results show a statistically significant increase of KD in the REMSD rats compared to both CONTROL and LP groups. There were no statistically significant differences in th B max among the experimental groups. There was also no change either in cortical activity of K + stimulated p-nitrophenylphosphatase, the dephosphorylation reaction of phosphorylated sodium–potassium/ATPase or in Mg 2+-stimulated p-nitrophenylphosphatase. An increase in the KD of [ 3H]-ouabain binding to the sodium–potassium/ATPase in REMSD rats indicates a lower affinity to the endogenous inhibitors/stimulators of the enzyme. Therefore, this decreased affinity of the endogenous ouabain-like substances may be involved in the increased excitability induced by REMSD.