Persistent firing recorded with perforated patch clamp method. A, An example of no persistent firing response in normal ACSF. A current injection (1 s, 100 pA; shown in B, bottom trace) drove spiking during stimulation but did not induce persistent firing. B, An example of long-lasting persistent firing induced in Cch (2.5 μM). C, Frequency of persistent firing in different pharmacological conditions. D, Plateau potential in different pharmacological conditions.