Figure 1. Experimental schedule, probe tip locations, and immunohistochemistry. A, Experimental schedule. EEG and EMG were recorded continuously. On the control day before SD, aCSF perfusion began just after lights-on; perfusion stopped, and the animals were disconnected from the microdialysis tubing 30 min before lights-off. The SD experiment was similar to the control day, except for the 6 h SD by gentle handling (Franken et al., 1991), which began 2.5 h after lights-on. Microdialysis samples (flow 1 μl/min) were collected every 30 min. On the 24 h control day and during subsequent drug perfusion experiments, aCSF perfusion began 22–24 h before the control day began. Histamine perfusions were performed from ZT 3–6 (light period), and histamine receptor 1 antagonist perfusions took place between ZT 15 and 18 (dark period), after which aCSF perfusion remained continuous. B, Probe tip locations were marked with ink injected through a modified microdialysis probe. All probe tips were located between −0.26 and −0.80 mm from bregma (Paxinos and Watson, 1998). Black squares indicate the location of the probe tip; if more than one tip was located in the same place, only one representative square is depicted. A representative coronal brain section showing the microdialysis probe track is shown in the lower right corner. C, ChAT- positive neurons in the BF of a control animal (top) and after a local 192IgG-saporin lesion (bottom); 20× magnification. Ctrl, control; SAP, 192IgG-saporin lesion.