Figure 1.

Evaluating synapses using unbiased stereology and electron microscopy (physical disector). a, Set of four electron micrographs overlaid with counting frames and taken from corresponding areas of four ultramicrotome serial sections in the BLA. Blue asterisks mark the tops of synapses. Tops were counted if they were within the counting frame or on the inclusion (green lines) but not the exclusion lines (red lines). Each micrograph was used as the reference and the look-up section with its matching pair. Tops of synapses are labeled according to their membrane specialization [asymmetric (as)] and their postsynaptic target [spine (sp)]. The scale bar in the lower right panel equals 1 μm and is valid for all four panels. b, High-power view of the area within the black box drawn on the left side of each of four sections in a. In panel 2, an asymmetric axospinous synapse is considered a top of a synapse because a synaptic cleft, postsynaptic density, and neurotransmitter vesicles are apparent in panel 2 but not 1. Similarly, in panel 3, an asymmetric axospinous synapse is considered a top of a synapse because a synaptic cleft, postsynaptic density, and neurotransmitter vesicles are apparent in panel 3 but not 2. Scale bar: panel 4 (for panels 1–4), 500 nm.