The effect of arachidonic acid on the A current (I-A) has been studied
in dissociated bullfrog neurons under whole-cell voltage-clamp condit
ions. Arachidonic acid reduced I-A in a dose-dependent and reversible
manner without a shift in the prepulse inactivation voltage-current re
lation. 1.75 mu M inhibited I-A by 50%, and higher concentrations caus
ed a total suppression. In addition, arachidonic acid increased the M-
current (I-M), a different potassium current that does not inactivate.
Neither indomethacin nor nordihydroguaiaretic acid, cyclooxygenase an
d lipoxygenase inhibitors respectively, prevented I-A reduction. In co
ntrast, nordihydroguaiaretic acid prevented I-M enhancement. Eicosatet
raynoic acid, an arachidonic acid analog that cannot be metabolized, a
lso reduced I-A. These results suggest that arachidonic acid metabolis
m is not required to suppress I-A.