EFFECTS OF CARBAMYLCHOLINE AND ATROPINE 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 carbamylcholine and atropine on the incorporation in vivo of ³³P_i into individual phospholipids of rat brain were studied at 5, 15 and 30 minutes after intracisternal injection of the radionuclide. After five minutes, carbamylcholine, simultaneously injected with the ³³P_i, stimulated the labeling of phosphatidic acid (PA) and phosphatidyl inositol (PI). After 15 and 30 minutes, there was a marked stimulation of the turnover of phosphatidyl choline (PC) in contrast to the percent stimulation of PI which decreased and the stimulation of PA which was no longer evident. Carbamylcholine did not affect the labeling of any of the remaining phospholipids. Atropine, injected i.p. 15 minutes before the ³³P_i, blocked completely the carbamylcholine-stimulated labeling of PA, PI and PC. These studies suggest that the metabolism of PA and PI in rat brain are associated with rapid membrane changes sensitive to cholinergic mechanisms and that the metabolism of PC, also affected by cholinergic mechanisms, is related to slower membrane processes.