Quenching revisited: low level direct current inhibits amygdala-kindled seizures.

We have reported that low frequency stimulation (1 Hz for 15 min), applied after kindling stimulation of the amygdala, inhibited the development and expression of amygdala-kindled seizures, an effect we termed quenching. Subsequently, we discovered that this effect could only be achieved when certain stimulators were used that also emitted a low-level direct current (DC). The studies reported here indicate that DC, applied once daily for 15 min at intensities of 5-15 microA, produced an intensity-related attenuation of kindling development and an increase in the afterdischarge threshold. This effect persisted in some animals for at least 1 month after discontinuation of the DC. In fully kindled animals, a robust increase in seizure threshold and persistent seizure inhibition were also observed using 10 microA of DC administered for 14 days. These results clarify and extend our original findings of a quenching effect; however, the mechanisms by which low level DC induces quenching require further elucidation.