Figure 2:

Role of SER and polyribosomes in supporting synaptic growth after LTP. A) Electron micrographs and A’) 3DEMs of dendritic spines without SER, with a simple tubule of SER, or a fully elaborated spine apparatus (SA). B) Following LTP in adults, the frequency of SER containing spines does not change; however, there is a significant shift from a single tubule (T) to the SA form of SER (*, p<0.5, n= number of spines in each condition). C) Electron micrograph and C’) 3DEM of spine containing a polyribosome, but no SER. D) The LTP-related synapse enlargement is minimal in spines lacking PR or SER, is greater on spines that retain PR, and is greatest on spines containing SER. Each graph illustrates the actual PSD areas, controlled for head diameter, and plotted on a log-normal scale, with correlation values (R²), and results of ANCOVA (p values and effect sizes, η²). E) At P15, most of the new spines produced 2 hours after LTP induction have small synapses and contain no SER. F) 3DEM of dendritic segment from P15 illustrating secretory compartments increase in spines after LTP. G) At P15, the increased secretory elements are primarily small vesicles (sv) or recycling compartments (RC) while some are also coated pits (cp) coated vesicles (cv) or large clear vesicles (LV). Amorphous vesicles and degradative structures are not elevated significantly.