Fig. 3.

Combined application of organic Ca²⁺ channel antagonists fails to block bursting.A, Ca²⁺ channel blockers were sequentially added to the ACSF, and the efficacy of Ca²⁺ channel blockade was assessed by the progressive block of the EPSP evoked by orthodromic stimulation of the Schaffer collaterals (Aa₂–Ae₂). Combined application of organic Ca²⁺antagonists did not block bursting (Aa₁–Ad₁) but additional application of 50 μmNi²⁺ did (Ae₁). Blockers were applied for at least 30 min (ω-conotoxin GVIA 1 μm, 62 min; ω-agatoxin TK 300 nm, 40 min; nicardipine 10 μm, 30 min; Ni²⁺ 50 μm, 50 min).