Desipramine treatment does not block MEND, whereas BEL treatment blocks MEND but not exocytosis. (A) ATP-dependent MEND in response to a Ca transient is unchanged by the pretreatment of cells with 100 µM desipramine for 1 h in serum-free media, followed by further incubation with 100 µM desipramine for 1 h and execution of experiments with 100 µM desipramine in both cytoplasmic and extracellular solutions. (B) Similar treatment with desipramine fails to inhibit spermidine-dependent MEND in the absence of ATP. (C) Same solutions as in A. BHK-NCX1 cells, which were pretreated with 50 µM BEL for 1 h in serum-free media, show robust Ca-activated exocytosis, with Cm doubling over three Ca influx episodes while endocytic responses are potently inhibited. (D) Same solutions as in B, with BEL treatment as in C. BEL treatment does not block exocytic responses that occur in the absence of ATP and presence of cytoplasmic spermidine (1 mM). However, endocytic responses are completely suppressed.