FIGURE 8.

Presynaptic expression of mGlu3 in layers II/III and V of rat PFC. (A,B) In layer II/III, a moderate presynaptic component of mGlu3 is captured in glutamatergic-like axons terminals establishing asymmetric synapses both near the synaptic active zone (A), and extrasynaptically near a mitochondrion (B). One of the two spines in (B) is also labeled. The synaptic cleft is magnified and highlighted with light green shading in (A) to better show the location of mGlu3 labeling in relationship to the synapse. (C–F) Bundled preterminal axons typically express mGlu3 at the plasma membrane. (G–K) In layer V, presynaptic mGlu3 can be visualized perisynaptically on membranes flanking the synapse (G,H), and near presynaptic vesicles (G–I), with an additional component in preterminal axons (J,K). Preterminal axons are shown both in cross-section (e.g., C), and in longitudinal section (e.g., D) for comparison. Synapses are between arrows. Red arrowheads point to mGlu3 immunoreactivity on axons; yellow arrowheads in (B) indicate additional mGlu3 labeling on a spine. Profiles are pseudocolored for clarity. as, astrocyte; ax, axon; den, dendrite; mit, mitochondrion; sp, spine. Scale bar: 200 nm.