Figure 2.

DRN 5-HT responses to inescapable tail-shock stress with either Safe or Random signals. A, Mean (±SEM) levels of extracellular 5-HT expressed as percentage of baseline. Samples were collected at 20 min intervals before shock (B1–4), during shock (S1–4) and after shock (P1–4). The black bar indicates the duration of the 100 tail shocks. B, 10× photomicrograph of the caudal DRN (Bregma −8.30 mm). Solid line illustrates the border of the DRN and the dashed box represents the field magnified on the right. C, 20× photomicrograph within the DRN illustrating neuronal soma stained positive for 5-HT (enclosed in a diamond), Fos (enclosed in a circle) and double-labeled Fos and 5-HT (enclosed in a square). D, Mean (+SEM) percentage of neurons double-labeled for Fos and 5-HT in the caudal DRN. Filled circles/bar indicate stress with safety signals and open circles/bar indicate stress with random signals.