Figure 9.
NO-synthase signaling pathway is necessary for the expression of the metaplastic effect of apamin on LTP. (A) When L-NAME, an inhibitor of NO-synthase, was applied 20 min before and 20 min after LTP induction, it prevented prior application of apamin from transforming the S-LTP usually triggered by a single stimulation train into an L-LTP. In this case, the time course of the increase in the slope of the fEPSP triggered by one train of HFS delivered after prior application of apamin (○) was not different from that observed when no drug was applied (●). (B) When L-NAME was coapplied with apamin, it did not prevent apamin from having a metaplastic effect on LTP. In this case, the time course of the increase in the slope of the fEPSP triggered by a single stimulation train corresponded to the profile of an L-LTP whether apamin was applied 45 min before LTP induction with L-NAME (◽) or without (○).