Figure 3.

Effect of prior application of apamin on the duration of LTP when the pre-LTP induction duration was as long as 2 h 30 min (after the recovery period). Each part of the figure compares the time course of the fEPSP slope 2 h 15 min before and 3 h after the delivery of a single train of HFS. (A) When Mg²⁺ concentration was 1 mM, an application of apamin lasting 1 h 15 min and ending 45 min before LTP induction did not modify the characteristics of LTP. In fact, the control LTP was improved as a result of the longer duration of the baseline. Compare this control LTP with that displayed in Fig. 1A. (B) When Mg²⁺ concentration was 1.3 mM, the duration of LTP was increased by prior application of apamin (with respect to the control LTP recorded at that Mg²⁺ concentration). (C) When Mg²⁺ concentration was 1.3 mM and when application of apamin was stopped 1 h before LTP induction (instead of 45 min in B), prior application of apamin no longer had any influence on LTP.