INHIBITOR OF LIPOXYGENASES BLOCKS MODULAT ION OF CHOLINORECEPTOR PLASTICITY EVOKED BY 15-HETE

The role of acyclic eicosanoids in the modulation of the plasticity of somatic cholinoreceptors, due to 15(S)-hydroxy-(5Z,8Z,11Z,13E)-eicosa tetraenoic acid (15-HETE), was studied in identified neurons of Helix lucorum. Lypoxigenase inhibitor, nordihydroguaiaretic acid blocks the effects of 15-HETE on the extinction of the inward current, evoked by the rhythmic application of acetylcholine on the neuron. The conclusio n was reached that the short-latency effect of 15-HETE, on the plastic ity of cholinoreceptors is due to the inhibition it produces on the 5- lipoxygenase. This effect leads to a lowering on the level of acyclic eicosanoids which are formed by the action of this enzyme. The potenti ation of the effect of the acyclic eicosanois, whose synthesis is rene wed in the second phase, is a plausible explanation of the long-latenc y modulatory effect of 15-HETE.