Figure 11. Model depicting the acquisition of release heterogeneity over three days of NMJ development.

(A) Presynaptically, Ca²⁺ channels (yellow) and BRP (blue) are added over time to increase release probability. Postsynaptically, GluRIIA and GluRIIB are added during maturation and eventually segregate at high releasing sites. (B) The number of AZs roughly doubles every 24 hr, with all new AZs having low release probability (blue dot). AZs increase in release probability over time and eventually reach high P_r status (red dot).