Summary and schematic model. (A) Summary of the multiplicity data obtained in Figures 1-3. ANOVA and Bonferroni post hoc test shows a significant difference between AMPA multiplicity in pyramidal cells from young adult animals and AMPA multiplicity in interneurons of both P7-18 rats and young adult rats (P = 0.004 and P = 0.02, respectively, left panel), but no significant differences between the groups of the right panel. (B) Schematic model illustrating the development of connectivity onto pyramidal cells and interneurons in stratum radiatum. Inhibitory (red) axons form multiple connections already in the P7-18 rats, whereas the excitatory (green) axons start out with single release site connections (left panel). During development excitatory axons grow multi release site connections onto pyramidal cells, but not to interneurons in stratum radiatum (right panel).