EFFECTS OF SYMPATHOMIMETIC DRUGS ON INCORPORATION IN VIVO OF INTRACISTERNALLY INJECTED ³³P_i INTO PHOSPHOLIPIDS OF RAT BRAIN

¹ Departments of Psychiatry and Pharmacology, Duke University Medical Center, Durham, North Carolina

The effects of norepinephrine, phenylephrine, isoproterenol, phenoxybenzamine and carbamylcholine on the incorporation in vivo of ³³P_i into phospholipids of rat brain were studied at 5 aumd 30 minutes after intracisternai injection of the radionuclide. Norepinephrine, an alpha and beta adrenergic stimulator, and phcnylephrine, an alpha adrenergic stimulator, enhaneed the labeling of phosphatidic acid and phosphatidyl inositol at both times, whereas isoproterenol. a beta adrenergic stimulator, had no effect. Phenoxyhenzamine, an alpha adrenergic blocking agent, blocked the stimulatory effect of norepinephrine and phenylephrine. The pattern of stimulatin of individual phospholipids by norepinephrine was different from that of carbamylcholine, a cholinomimetic agent, in that norepinephrine had a sigimificantly greater effect on the labeling of phosphatidic acid and had no effect on the labeling of phosphatidyl choline, a phospholipid markedly stimulated by carbamylcholine. These studies suggest that time metabolism of phosphatidie acid and phosphatidyl inositol in rat brain is associated with rapid membrane processes controlled in part by alpha adrenergic mechanisms and differ from the effects on phospholipid metabolism which are produced by cholinergic mechanisms. The data also indicate that the metabolism of phosphatidyl choline may be related to slower menmbrane Processes controlled by cholinergic mechanisms.