Figure 1.

Dopaminergic but not serotoninergic neurons in the vPAG contain Fos protein during wakefulness but not sleep. Immunohistochemical dual labeling of TH (brown) and Fos (black) is shown in animals that are spontaneously awake (A), kept awake by 2 h of environmental stimulation (B), and are spontaneously asleep (C). Fos-positive TH-ir neurons were seen only during wakefulness (arrows). In contrast, no double-labeled neurons were seen in immunohistochemical dual-labeling of serotonin (5-HT; brown) and Fos (black) in a spontaneously awake rat (D). Aq, Cerebral aqueduct; F wake, forced wakefulness. Scale bar: (in C) A, B, 200 μm; C, D, 100 μm. Arrows point to double-labeled neurons; arrowheads mark single-labeled neurons. An asterisk (*) marks the reference location in the inset box.