n-6 polyunsaturated fatty acids increase the neurite length of PC12 cells and embryonic chick motoneurons.

We have tested the action of three n-6 polyunsaturated fatty acids, either free or in the form of ethyl esters, on the neurite outgrowth in two neuronal models: a rat pheochromocytoma cell line (PC12) and embryonic chick motoneurons, after 7 days in culture. An inverted microscope coupled with the 'VIDS 4' software was used for measuring the neurite length. Free fatty acids were found to be cytotoxic at 10(-3) M and the maximal increase of the neurite length was obtained at 10(-5) M. In contrast, fatty acids in the form of ethylesters were not cytotoxic and at 10(-3) M induced the maximal increase in the neurite length. This increase (1.2 to 2 fold) significantly differed from the control and was dose-dependent. These results were discussed in relation to the action of fatty acids on enzyme activation and membrane fluidity.