Some
anesthetics bind and potentiate γ-
aminobutyric-acid-type receptors, but no universal mechanism for
general anesthesia is known. Furthermore, often encountered complications such as
anesthesia induced
amnesia are not understood.
General anesthetics are hydrophobic molecules easily dissolving into
lipid bilayers. Recently, it was shown that
general anesthetics perturb phase separation in vesicles extracted from fixed cells. Unclear is whether under physiological conditions
general anesthetics induce perturbation of the
lipid bilayer, and whether this contributes to the transient
loss of consciousness or
anesthesia side effects. Here we show that
propofol perturbs
lipid nanodomains in the outer and inner leaflet of the plasma membrane in intact cells, affecting membrane nanodomains in a concentration dependent manner: 1 μM to 5 μM
propofol destabilize nanodomains; however,
propofol concentrations higher than 5 μM stabilize nanodomains with time. Stabilization occurs only at physiological temperature and in intact cells. This process requires ARP2/3 mediated actin nucleation and
Myosin II activity. The rate of nanodomain stabilization is potentiated by GABAA receptor activity. Our results show that active nanodomain homeostasis counteracts the initial disruption causing large changes in cortical actin. SIGNIFICANCE STATEMENT:
General anesthesia is a routine medical procedure with few complications, yet a small number of patients experience side-effects that persist for weeks and months. Very young children are at risk for effects on brain development. Elderly patients often exhibit subsequent
amnesia. Here, we show that the
general anesthetic propofol perturbs the ultrastructure of the
lipid bilayer of the cell membrane in intact cells. Initially
propofol destabilized
lipid nanodomains. However, with increasing incubation time and
propofol concentration, the effect is reversed and nanodomains are further stabilized. We show that this stabilization is caused by the activation of the actin cortex under the membrane. These perturbations of membrane bilayer and cortical actin may explain how
propofol affects neuronal plasticity at synapses.