Figure 4.

Postsynaptic expression of mGluR2 in monkey dlPFC. (A,B) mGluR2 is weakly expressed in dendritic spines perisynaptically. Its association with the glutamatergic-like synapse is selective to stubby (A) and mushroom-type (B) spines; in B, the obliquely sectioned synaptic disk is marked with oval. (C,D). However, mGluR2 in spines is primarily an extrasynaptic receptor. Remarkably, mGluR2 was distinctly associated with the plasma membrane facing the spine apparatus. This is best appreciated in the edited images C and D, where the synaptic cleft is marked in green and the apparatus is pink-pseudocolored. Note also the astrocytic as well as axonal labeling for mGluR2. Labeled axons (ax), dendrites (den), spines (sp), and astrocytes (as) are pseudocolored for clarity; color-coded arrowheads point to mGluR2; synapses are between arrows. Scale bars, 200 nm.