Do general anaesthetics perturb lipid membranes? The role of cholesterol.

The effect of enflurane and methoxyflurane on the permeability of liposomes to H+ was rested. Liposomes were prepared with phospholipids alone or as mixtures of cholesterol and phospholipids having the ratios of 1:2 or 1:1. Both anaesthetic drugs facilitated the release of H+ from pure phospholipid liposomes and from those with a 1:2 ratio. The facilitated release of H+ was prevented by the presence of high concentrations of cholesterol. As the cholesterol:phospholipid ratio in synaptic vesicles is of the order 1:2, it is expected that their permeability might be affected by volatile anaesthetics, leading to a modification of synaptic transmission.