Fig. 3.

The decrease in the efficiency of exocytosis was dependent on the amount of the RRP released. A, Capacitance responses to paired-pulse stimuli lasting 2 msec. Theleft trace shows responses to depolarizations to −28 mV, and the right trace shows responses to depolarizations to −15 mV from the same terminal. The interval between pulses was 100 msec, and each pair was followed by an emptying stimulus delivered after 200 msec. B, The relationship between the decrease in the efficiency of exocytosis and depletion of the rapidly releasable pool of vesicles. Results collected from 16 terminals. The paired stimuli were 2–20 msec in duration, and interpulse intervals were 50–200 msec. The decreased efficiency of exocytosis reached a maximal value of ∼76% (dashed line) when >40% of the RRP was released.