Fig. 1. Hypnotic doses of halothane fail to depress activity of orexinergic neurons as determined by double-label immunohistochemistry. Coronal sections through perifornical hypothalamus reveal characteristic c-Fos protein expression (red nucleus) in orexinergic neurons (green cytoplasm) of ( A ) a nonanesthetized oxygen control mouse or ( B ) a halothane-anesthetized mouse. Arrows mark double-labeled neurons (examples shown as insets A-1 and B-1 ). Arrowheads mark orexinergic neurons lacking c-Fos nuclear expression (examples shown as A-2 and B-2 ).