Anatomical correlation. (A) Histologic locations of distal-most aspect of stimulating electrode as shown on necropsy with a representative section shown in the insert. In each instance, the stimulating electrode was located within 1 mm of the area deemed to be most consistent with the LC. Symbols on the left side of the templates represent experiments done in the presence of 7.5 mM PTZ and symbols on the right side of the templates represent experiments done in the presence of 15 mM PTZ. Open circles represent experiments done in the presence of PTZ alone. Filled circles represent experiments done in the presence of PTZ and 10 mM valproic acid. Red dots represent experiments done in the presence of 15 mM PTZ using 0.1 μC of charge (0.5 mM/0.2 milliseconds) per stimulation. All other experiments were performed using 0.01 μC of charge (0.1 mM/0.1 milliseconds) per stimulation. OB, olfactory bulb; TEL, telencephalon; CER, cerebellum; MED, medulla; SC, spinal cord; IL, inferior lobe; LC, locus coeruleus. (B) Reactive hindbrain stimulation using a far caudal stimulation site. Following a latency after PTZ application (down arrow) the scalar entropy (blue) fell and stimulation was triggered (red asterisks). Despite stimulation, an electrographic seizure occurred as evidenced by the increased amplitude of the cerebral field potential (black). A second round of stimulation terminated this seizure. These results imply that more caudal stimulation sites are less effective at attenuating seizures.