Effect of anesthesia on membrane fluidity and acetylcholinesterase activity in rat brain synaptosomes

Anesthesia by means of ketamine induces an increase of fluidity in the hydrophobic area of rat brain synaptic membranes, as proved by the spin label 16-doxyl stearate, in contrast with no change induced in the order parameter of 5-doxylstearate that probes the membrane surface. These effects are qualitatively similar to those observed by ketamine addition in vitro. On the contrary, acetylcholinesterase from synaptic membranes, although inhibited in vitro by ketamine, is activated in ketamine-anesthetised rats suggested that metabolic changes are at the basis of the effects observed in vivo.