Fig. 2.

Facilitation activated by paired action potentials with prolonged duration. A₁,A₂, and A₃illustrate IPSCs, presynaptic Ca²⁺ transients, and presynaptic action potentials, respectively. B, The first (dotted line) and second (solid line) IPSCs (B₁), Ca²⁺ transients (B₂), and action potentials (B₃) are superimposed and displayed at a higher time resolution. Although the second IPSC is facilitated, the duration of the second action potential is shorter than that of the first one. The Ca²⁺ transient activated by the second action potential also has a lower amplitude. This experiment was performed in the presence of 1 mm 4-AP and 20 mm TEA. Each trace represents the average of 100 trials.