Incorporation of Phosphate Into Rat Brain During Sleep and Wakefulness

Abstract

Labelled inorganic phosphate (32PI) was administered intraventricularly to unrestrained sleeping and waking adult rats. After about 20 min of sleep or a comparable period of wakefulness, as monitored by EEG and EMG, the animals were frozen in liquid nitrogen and the brains were analysed. One group of animals (A) was not previously acclimatized to the apparatus. A second group (B) was acclimatized. The specific radioactivity of a phosphoprotein fraction was elevated during sleep in group A but not in group B. The specific radioactivity of the phosphatides of group B was depressed in sleeping as compared with waking animals. This effect was not observed in group A. No significant difference was detected between the EEG patterns of sleeping animals in groups A and B, as evaluated by standard criteria. These observations suggest that the physiological conditions attributable to environmental, emotional or other determinants can influence shifts in brain metabolism during the sleepwakefulness cycle.THE SEARCH for biochemical changes in the brain that are related to the sleepwakefulness cycle has been intensified in recent years (BOBILLIER, SAKAI, SEQUIN and JOUVET, 1971 ; VAN DEN NOORT and BRINE, 1970). We have previously reported observations on the incorporation of inorganic phosphate into a chemical fraction of the brains of immature (21-day-old) rats during sleep (REICH, DRIVER and KARNOVSKY, 1967). A two-to three-fold increase in the specific radioactivity of phosphate was detected in the hot trichloracetic acid (TCA) extract of the brains of sleeping animals in comparison to those from waking controls. The phosphorus in this extract was present as inorganic phosphate that had been split by hot TCA from a more complex substance in the residue that remained after we had removed lipids, nucleotides and other phosphorus-containing substances of the brain. In a second study we found that brain levels of carbohydrate metabolites varied with sleep and wakefulness and that the results were dependent upon the acclimatization of animals to the experimental apparatus (REICH, GEYER and KARNOVSKY, 1972).The work we now report had several aims. The first was to extend from baby rats to mature rats the earlier study on the incorporation of inorganic phosphate into brain fractions. The second was to perform the experiments under conditions in which the physiological state of the animals (sleeping vs waking) was rigorously monitored-a situation not possible with the 21 -day-old animals. The third aim was to investigate the influence of prior treatment of the rats on the incorporation of inorganic phosphate into brain fractions. Acclimatization to the test situation was chosen. A fourth objective was to obtain additional information on the nature of the acid-labile phosphatecontaining substance(s) affected by sleep. These experiments have been made possible by the use of a preparation that enables us to infuse labeled substances into the lateral ventricles of unanaesthetized, freely-moving adult rats while monitoring the electroe...

Influence of Synchronized Sleep on the Biosynthesis of RNA in Two Nuclear Classes Isolated from Rabbit Cerebral Cortex

“…At the appropriate time the precursor was injected at a rate of 25-50 pl/min. This procedure was adapted from Reich et al (1973).…”