Fig. 10.

Electron micrographs showing immunoreactivity for mGluR2/3 (A, C, D, E) and mGluR2 (B) in CA1 stratum lacunosum moleculare (A–C), CA3 stratum lucidum (D), and CA1 stratum radiatum (E) as detected by preembedding immunoperoxidase (A, B, D, E) and immunogold (C) methods. A, Peroxidase reaction product for mGluR2/3 is accumulated intracellularly in a preterminal axon (arrows), which is continuous to an unlabeled axon terminal making asymmetrical synapses (arrowheads).B, Peroxidase reaction product for mGluR2 is accumulated extracellularly along axons and axon terminals (double arrowheads), but not in the synaptic clefts of asymmetrical synapses (arrowheads). C1, C2, andC3 were taken from three serial sections. Silver-enhanced immunogold particles for mGluR2/3 are found along a preterminal axon (arrows), which is continuous to an axon terminal making unlabeled asymmetrical synapses (arrowheads).Open and closed stars indicate corresponding regions in the serial sections. D, Peroxidase labeling for mGluR2/3 is observed in mossy fibers (arrows), one of which (asterisk) is continuous to a giant mossy fiber terminal (MT) making unlabeled asymmetrical synapses (arrowhead) with spines of CA3 pyramidal cells. E, Glial processes are also labeled for mGluR2/3. Scale bar, 0.5 μm.