Effects of the monoamine oxidase inhibitors on [3H]CDP-diacylglycerol accumulation and phosphatidylinositide synthesis. Cortical slices were tested with indicated concentrations of phenelzine or hydralazine. CDP-diacylglycerol (CDP-DG) levels were analyzed as outlined under Figure 1, while phosphatidylinositide (PI) synthesis was measured as the total pool of extractable [3H]inositol-labeled phospholipids as in Figure 2. Each point is the mean ± SEM (N = 9). Each drug stimulated significant concentration-dependent accumulations of CDP-diacylglycerol (ANOVA, p < 0.001 for each drug) and phosphatidylinositide synthesis (ANOVA, p < 0.001 for each drug). Note that if individually compared to the corresponding control measure, each of the tested concentrations from 0.1 – 300 μM gave statistically significant effects on CDP-DG and PIs. Note also the greater relative accumulation of PIs compared to the accumulation of CDP-DG.