Synaptic Reorganization of the Perisomatic Inhibitory Network in Hippocampi of Temporal Lobe Epileptic Patients

Figure 3

High magnification light micrographs (a–d) show the somata (upper panels) and the axonal cloud (lower panels) of PV-positive cells in the human control (a) and epileptic (b–d) CA1 region. The number of PV-positive elements decreased with the degree of cell loss in the human epileptic CA1 region. PV-stained axons (lower panels) formed a dense network in the stratum pyramidale of the CA1 region as long as their postsynaptic targets, that is, pyramidal cells, are present (b, c). Note the basket-like formation on (a)–(c) (arrowheads) and chandelier-like formation on (b) (double arrowheads). In the sclerotic CA1 region lacking principal cells hardly any PV-positive axons can be seen (d). Scale bar: (a–d) 20 μm. Electron micrographs show PV-stained axonal boutons contacting pyramidal cell somata (e, f) in the control (e) and epileptic (f) CA2 region. Axon initial segments (AISs, (g) and (h)) were the other main targets of PV-positive axons in the human control (g) and epileptic (h) CA1 region. Scale bars: (a)–(d) 20 μm; (e)–(h) 1 μm.

(a) Control

(b) Epileptic (mild)

(c) Epileptic (patchy)

(d) Epileptic (Sclerotic)

(e) Control (CA2)

(f) Epileptic (CA2)

(g) Control (CA1)

(h) Epileptic (CA1)