Eicosapentaenoic acid inhibits vasoconstrictor- and noradrenaline-potentiating effects of neuropeptide Y in the isolated rabbit ear.

The vasoconstrictor effect of neuropeptide Y (NPY) was compared with that of noradrenaline (NA) in the isolated perfused rabbit ear. Phentolamine at a concentration which completely abolished the effect of NA, did not diminish the effect of NPY. The combined vasoconstrictor effect of NPY and NA was significantly stronger than the calculated effect of an additive interaction, but not significantly stronger than an independent combination. This can be interpreted as an overadditive effect, and may be an indication for different points of attack with independent actions of these two transmitters in the vessels of the rabbit ear. Eicosapentaenoic acid (EPA) dose-dependently antagonized the effect of NPY to a similar degree as that of NA. In the presence of indomethacin (8.6 mumol/l), neither the effect of NPY nor that of EPA was changed. Moreover, EPA (33 mumol/l) diminished the combined vasoconstrictor effect of NA and NPY. These findings indicate that EPA is a non-selective antagonist of sympathetic transmitters in small peripheral vessels and excludes an interaction at specific receptors.