Figure 4.

“Kiss and run” in normal synaptic transmission. (A) Predicted and observed percentage of “kiss and run” events as a function of hypertonicity. Theoretical function is , where h is the hypertonicity in osmolars, with a = 2.3 and h₀ = 0.65. Experimental points are derived from those in Fig. 1. Note that p(0) = 18.3%, which corresponds to the percentage of action potential-evoked exocytotic events that are “kiss and run.” (B) Cartoon of three pathways. (1) “Kiss and run,” in which the fusion pore opens and then closes to return the vesicle to its docked state intact; (2) rapid endocytosis that requires dynamin to pinch the vesicle membrane off from the surface membrane, but not clathrin; and (3) the classical endocytic pathway that requires both dynamin and a clathrin coat that is removed after endocytosis.