Effects of pressure and the local anesthetic tetracaine on dihexadecylphosphatidylcholine bilayer membrane

Abstract

The temperature ( T)-pressure ( P) phase diagram of ether-linked dihexadecylphosphatidylcholine (DHPC) multilamellar vesicles was constructed by the method of high-pressure transmittance in the presence of the local anesthetic tetracaine hydrochloride (TC HCl). While the temperature of the main transition from the ripple gel (P′ β) phase to the liquid crystal (L α) phase was depressed by the addition of TC HCl and elevated by the pressure, the temperature of the pretransition from the interdigitated gel (L βI) phase to the P′ β phase was elevated by both the addition of TC HCl and pressure. The P′ β phase disappeared at a TC HCl concentration over 10.0 mmol kg −1 at ambient pressure and at pressure above 130 MPa in the absence of TC HCl. The region of the P′ β phase on the phase diagram was narrowed by the effects of both pressure and TC HCl. On the other hand, pressure and TC HCl stabilized the L βI phase, extending its region on the phase diagram. The pressure-anesthetic antagonism for only the main phase transition was confirmed and a synergistic effect of pressure and anesthetic was observed for the pretransition of DHPC bilayer membranes.