Fig. 10.

Endocytosis was induced by depolarization and Ca²⁺ influx. A bipolar cell was superfused with an extracellular saline containing 100 nmCa²⁺. Timing traces indicate an 18 sec application of 20 μm FM1–43, an 18 sec application of 20 μm FM4–64, and 6 sec applications of a high Ca²⁺ and K⁺ saline.s is the fluorescence intensity of the surface membrane.v_n is the fluorescence of endocytosed vesicles that remain trapped in the cytoplasm. Transient endocytosis was measured as T_n = ρv_n/s. After superfusion with the high Ca²⁺ and K⁺ saline,T_n was 0.08 MEq. Insets, Images of the terminal taken at the times marked a andb are shown. The gain in b is eight times the gain in a. Scale bar, 10 μm.