Effects of Electrical Stimulation by A. M. Pumphrey

1. The incorporation of [32P]phosphate into phospholipids was measured in slices cut from the pial surface of guinea-pig cerebral cortex; incorporation into the phosphorus of some water-soluble precursors of phospholipid was measured under similar conditions. 2. Slices subjected to overall electrical stimulation at a frequency of 5pulses/sec. differed from control slices in their pattern ofphospholipid labelling. After 1 hr. ofstimulation, incorporation of[32P]phosphate into phosphatidylcholine, ethanolamine phospholipid and cardiolipin was respectively 54, 55 and 58% of the control value, and that into phosphatidylinositol was 186% ofcontrol. Phosphatidic acid labelling tended to increase with electrical stimulation, but the statistical significance of this change was marginal. Labelling of phosphatidylglycerol and diand tri-phosphoinositides was not affected significantly by electrical stimulation. 3. Electrical stimulation of the tissue altered the specific radioactivities of watersoluble precursors of phospholipid. 4. The turnover rates of the phosphate groups of phospholipids were estimated approximately from the specific radioactivities of phospholipids and their precursors. Phosphatidylinositol (and its lipid-soluble precursors) showed the largest change in turnover rate in response to electrical stimulation of the tissue; the turnover rates of other lipids were also affected. Changes in the specific radioactivity ofphospholipids did not correspond to changes in turnover in these experiments.