(A) Timeline.
(B1) Schematic of the hippocampal trisynaptic circuit showing the potential pathways for the spread of seizure activity (dashed arrows).
(B2) 473 nm of light was aimed at the IML, and extracellular field potentials were recorded in the IML, CA3, CA1, and subiculum cell layers (Xs).
(C1) A brief light pulse (2 ms; blue arrow) evoked a field EPSP in the IML (black arrow). Epileptiform discharges were recorded at increasingly longer delays in CA3, CA1, and the subiculum (see black arrows and C2), suggesting propagation along the trisynaptic circuit.
(D1) Epileptiform activity in CA3 and the subiculum was blocked by DCG-IV (2 μM), an antagonist of mossy fiber transmission (D2), which was reversed after 30 min in DCG-IV-free conditions (D3).
See also Figures S4 and S5.