NITROUS-OXIDE AND XENON ENHANCE PHOSPHOLIPID-N-METHYLATION IN RAT-BRAIN SYNAPTIC PLASMA-MEMBRANES

Halothane and isoflurane increase the rate of phospholipid methylation (PLM) in rat brain synaptosomal membranes, a process linked to the co upling of neuronal excitation to neurotransmitter release. In contrast , synaptic plasma membrane (SPM) Ca2+ ATPase (PMCA) pumping is reduced by exposure to halothane, isoflurane, xenon and nitrous oxide (N2O). To examine further the relationship between PLM, PMCA and anesthetic a ction, we investigated the effect of clinically relevant concentration s of two less potent anesthetic gases, N2O and xenon, on PLM in SPM. B iochemical assays were performed on SPM exposed to 1.3 MAC of N2O (2 a tm), 1.3 MAC of xenon (1.23 atm) or an equivalent pressure of helium f or control. N2O or xenon exposure increased PLM to 115% or 113%, respe ctively, of helium control (p < 0.02). Similar exposures to N2O or xen on depressed PMCA activity to 78% and 85% of control (p < 0.05). Obser vations that PLM and PMCA are both altered by a wide variety of inhala tion anesthetic agents at clinically relevant partial pressures lend s upport to a possible involvement and interaction of these processes in anesthetic action.