Fig. 11.

Pharmacologically blocking voltage-gated Ca²⁺ channels blocked Ca²⁺ influx and endocytosis. A bipolar cell was superfused first with an extracellular saline containing 100 nmCa²⁺ and then three times with FM1–43 and high Ca²⁺ and K⁺ saline. Each application was a sequence of 20 μm FM1–43 in control saline for 4 sec, FM1–43 in high Ca²⁺ and K⁺ saline for 4 sec, and finally FM1–43 in control saline for 12 sec. Nisoldipine (50 μm) was added to the extracellular salines during the second and third applications.T_n (measured as illustrated in Fig. 10) for the three sequential applications was 0.08, 0.006, and 0.003 MEq.