Figure 8.

CB₁-positive GABAergic axon terminals are intact in the epileptic human hippocampus. A–C, The electron micrographs show striking CB₁ immunoreactivity within GABAergic axon terminals (b_GABA) forming symmetric synapses (open arrowheads) in the inner third of stratum moleculare of the dentate gyrus. Dense accumulation of the end product of immunoperoxidase reaction (DAB) indicates that these GABAergic axon terminals are fully equipped with CB₁ receptors in both the control and the epileptic hippocampi. Glutamatergic boutons terminate on dendritic spine heads with typical asymmetric synapses (closed arrowheads), which is characterized by broad postsynaptic density. In the control sample, the glutamatergic axon terminal (b_GLU) is positive for CB₁ (A), whereas CB₁-negative boutons (asterisks) forming asymmetric synapses are shown in electron micrographs taken from the nonsclerotic (B) and sclerotic (C) samples. Note that CB₁-positive axon terminals forming inhibitory synapses are larger than those giving excitatory synapses. Scale bars, 0.5 μm.