Fig. 7.

Model for the control of endocytosis by VDCCs in nerve terminals. Upon VDCC activation, exocytosis is stimulated and endocytosis is blocked by high localized [Ca²⁺]_i concentrations at the active zone. Vesicle membrane can be retrieved once it clears the active zone, because the block of endocytosis is relieved and endocytosis is stimulated by lower [Ca²⁺]_i levels in the nonactive zone. Once stimulation is terminated and [Ca²⁺]_i decreases, endocytosis can occur from either location within the nerve terminal.