Changes in redox potential in rat brain tissue developing during episodes of paradoxical sleep

Paradoxical sleep is regarded by many authors as consisting of episodes of integrative brain activity, this view being based on data relating to changes in overall brain electrical activity (depression of electrocorticograms or the appearance in electrocorticograms of oscillations at the theta rhythm) and increases in neuron activity, data showing negative changes in the potential of the direct current, and data demonstrating increases in brain temperature and local brain blood flow, increases in glucose utilization, and increases in the levels of free oxygen in brain tissue. We have previously observed that episodes of paradoxical sleep are accompanied by increases in the redox potential of brain tissue (E) by several millivolts. In these experiments, we used a direct current amplifier with a low input resistance (1 Mohm), which decreased the true magnitudes of changes in E accompanying episodes of paradoxical sleep. One of the aims of the present work was to determine more accurate measures of the functional changes of this type of sleep, by using a direct current amplifier with a high input resistance (1 Gohm). The second aim of the present work was to obtain more accurate data on differences in changes in oxidative metabolism in different parts of the brain during episodes of paradoxical sleep, by making simultaneous recordings of E from two points of the brain, using several different combinations of pairs of points.