The effects of halothane and enflurane on rat brain synaptosomal sodium-potassium-activated adenosine triphosphatase

Synaptosomes, or nerve-ending particles, were isolated from the cerebral cortices of young rats by homogenization, differential centrifugation, and density-gradient centrifugation. The sodium-potassium-activated adenosine triphosphatase enzyme system [(Na+ plus K+)-ATPase] of these particles is believed to represent in vitro the sodium-potassium pump of the nerve terminal. Suspensions of synpatosomes were equilibrated with air containing various concentrations of halothane and enflurane, as determined by gas chromatography. Clinical concentrations of the anesthetics had no effect on (Na+ plus K+)-ATPase activity. Fourteen per cent halothane and 14.8 per cent enflurane in the gas phase resulted in 12 and 10 per cent inhibition, respectively, of (Na+ plus K+)-ATPase activity. These data confirm that interference with active cation transport by inhibition of neuronal (Na+ plus K+)-ATPase is not related to the mechanism of halothane or enflurane anesthesia. (Key words: Anesthetics, volatile, halothane; Anesthetics, volatile, enflurane; Metabolism, enzymes, ATPase; Nerve, synaptosomal ATPase; Theories of anesthesia, ATPase.).