Fig. 1. Experiment timeline. Before the onset of data acquisition the desflurane concentration sufficient for the loss of righting reflex was tested in each rat; this concentration was held constant throughout the rest of the experiment. Spontaneous electroencephalographic and behavioral responses were recorded throughout the experiment. Infusion cannulae were inserted after 20 min of baseline recordings. Drugs were infused in five consecutive 1-min blocks over the course of 10 min (start of infusion, vertical arrow ). Electroencephalogram recording continued for 1 h after completion of the infusion sequence. The total duration of each experiment was approximately 120 min. LORR = loss of righting reflex; EEG = electroencephalogram.