Fig. 5.

Onset of LTD induced by PP stimulation.A–C, Summary plots as described in Results and in Figure 1. A, Data from experiments in which PP stimulation produced no initial potentiation (n = 23). B, Same as in A, but for a heterosynaptic input (n = 26). C, Same as in A, but in the presence of d-AP-5 (50–100 μm) (n = 17). Thevertical lines denote the time of PP stimulation onset, and 1 min thereafter, respectively. Note in A–C that the depression is initiated already within ∼30 sec, i.e., within three or four stimuli.