INTERLEUKIN-6 INHIBITS LONG-TERM POTENTIATION IN RAT HIPPOCAMPAL SLICES

The effects of recombinant human interleukin-6 (rhIL-6) on long-term p otentiation (LTP) induced in the Schaffer collateral/commissural-CA1 p athway were examined using rat hippocampal slices. Field excitatory po stsynaptic potential was recorded in the stratum radiatum of the CA1 r egion. Ten-min applications of rhIL-6 (50-2000 U/ml), started 5 min be fore the tetanus, significantly inhibited the induction of LTP, and in high doses of rhIL-6 also inhibited short-term potentiation (over 200 U/ml) and post-tetanic potentiation (over 500 U/ml). The effects of r hIL-6 (500 U/ml) were completely abolished by the preincubation of the slices with monoclonal anti-IL-6 receptor antibody (16 mu g/ml) for 2 h. Heat-inactivated rhIL-6 had no effect on the synaptic potentiation . RhIL-6 affected neither the previously established LTP nor the basal synaptic transmission. These findings indicated that rhIL-6 modulated synaptic potentiation through the IL-6 receptor-mediated process in t he hippocampus, probably by affecting post- and presynaptic sites in t he CAI region. The possible mechanisms of the IL-6-induced suppression of the synaptic potentiation were discussed.