Membrane-Mediated Effect on Ion Channels Induced by the Anesthetic Drug Ketamine

Abstract

Anesthetic drugs have been in use for over 160 years in surgery, but their mode of action remains largely unresolved. We have studied the effect of (R)-(-)-ketamine on the biophysical properties of lipid model membranes composed of palmitoyloleoylphosphatidylcholine by a combination of X-ray diffraction and all-atom molecular dynamics simulations. In agreement with several previous studies, we do not find significant changes to the membrane thickness and lateral area per lipid up to 8 mol % ketamine content. However, we observed that the insertion of ketamine within the lipid/water interface caused significant changes of lateral pressure and a pressure shift toward the center of the bilayer. The changes are predicted to be large enough to affect the opening probability of ion channels as derived for two protein models. Depending on the protein model, we found inhibition values of IC(50) = 2 mol % and 18 mol % ketamine, corresponding to approximately 0.08 and 0.9 muM concentrations in the blood circulation, respectively. This compares remarkably well with clinical applied concentrations. We thus provide evidence for a lateral pressure mediated mode of anesthesia, first proposed more than 10 years ago.

Lipid Simulations: A Perspective on Lipids in Action

“…In this way, they activate membrane receptors that in turn initiate a signaling pathway (Escriba 2006). Interestingly, the idea of lipid therapy is similar in spirit to the recent idea discussed by Cantor for the mechanism of general anesthetics (Cantor 1997;Jerabek et al 2010). He proposed that anesthetic molecules could play a role in the activation of membrane proteins by changing the pressure profile of a lipid membrane.…”

Fullerene up-take alters bilayer structure and elasticity: A small angle X-ray study

“…during the formation of protein complexes; compare section 3.4), and (iii) expected changes in the lateral pressure profile of membranes may influence negatively the function of embedded membrane proteins (e.g. the opening and closing probability of membrane pores can get altered (Jerebek et al, 2010)). …”

Thermodynamic study of benzocaine insertion into different lipid bilayers

“…In this context, even when the argument for a lipid site action might be revived based on recent developments and research, 9 almost a century ago Meyer and Overton 10, 11 associated the potency of anesthetics with their solubility in a lipid bilayer, at a time in which the lipid bilayer structure had not even been described. It has been suggested that the solubility of anaesthetics in a lipid bilayer may cause a disturbance in membrane fluidity [12][13][14][15][16][17] that could affect the protein structure of sodium channel formation, and as a consequence of this perturbance, a conformational change in the ion channel could take place, resulting in the blockage of ion transduction.…”