Fig. 7.

FFA effect on population spike is blocked by a high Mg²⁺-containing medium. Recording was first made with an FFA-containing pipette (A), followed by a control pipette (Ct). The Mg²⁺-containing pipette (B) produced an increase in population spike, without affecting the slope of the EPSP; however, another pipette containing both Mg²⁺ and FFA was not as effective in increasing population spike as an FFA-containing pipette by itself. In the same brain location, bicuculline produced a marked increase in population spike (C), as seen above. In all of these recordings, made in approximately the same location, the slope of the EPSP was approximately the same. Calibration on the leftis the same for B and C.