Alterations of plasma membrane fatty acid composition modify the kinetics of Na + current in cultured rat diencephalic neurons

Abstract

Properties of inward Na ++ currents (I Na) were examined in dissociated diencephalic neurons whose plasma membrane fatty acid composition had been altered. These neurons were grown in a defined medium supplemented with essential fatty acids (EFA) of either the w3 class (linolenic acid, 18:3w3) or the w6 class (linoleic acid, 18:2w6), which resulted in a two-fold increase in the plasma membrane phospholipid polyunsaturated fatty acid (PUFA) concentration. The properties of the inward I Na of these neurons were compared with those of control neurons grown in the absence of any supplemented fatty acids. The I Na of neuronssupplemented with a non-essential fatty acid (NFA) of w9 class (oleic acid, 18:1w9) was also examined. Several properties have been modified to different degrees. The ratio of the amplitudes between the fast and the slow decay components as well as the time constant of the fast decay component changed consistently and reversibly with the membrane phospholipid PUFA composition. The current-voltage relationships, channel selectivity, rates of inactivation and recovery from inactivation did not change. Other parameters, such as time-to-peak and steady-state inactivation curves, have changed in EFA- and NFA-supplemented cultures and did not reverse completely. These findings demonstrate that the kinetics of I Na can be modified by fatty acid supplementation. These effects can be correlated, in part, with alterations in plasma membrane phospholipid fatty acid composition.