THAPSIGARGIN BLOCKS LONG-TERM POTENTIATION INDUCED BY WEAK, BUT NOT STRONG TETANISATION IN RAT HIPPOCAMPAL CA1 NEURONS

To elucidate the role of calcium release from internal stores during d ifferent paradigms of tetanisation in long-term potentiation (LTP), we have investigated the effects of thapsigargin on the elevation of the excitatory postsynaptic field potential (fEPSP) and the population sp ike (PS) after tetanisation. We found no effect on the duration of fEP SP potentiation if thapsigargin was perfused before strong (triple) te tanisation. However, the potentiation was reduced significantly from c ontrol experiments if thapsigargin was applied before weak (single) te tanisation. Surprisingly, we did not find any reduction of PS potentia tion, which could be due to changes in the recurrent inhibition. We co nclude that the involvement of internal calcium release in the mechani sms of LTP induction will be reduced if multiple tetanisation is used.