Fig. 1.

Extracellular adenosine concentrations during spontaneous wakefulness and sleep. (A) Chromatograms of the adenosine reference standard (left) and the basal forebrain microdialysis sample (right), both of which show peaks (arrows) at 8-min retention time. (B) Adenosine concentrations in 10-min consecutive samples from an individual microdialysis probe in the basal forebrain. Labels indicate the predominant behavioral state: W, wakefulness; S, slow wave sleep; and R, REM sleep. (C) Coronal schematic of the basal forebrain showing the sites of the tips of the six probes used for the prolonged wakefulness and NBTI perfusion experiments. All sites are mapped onto this one section, including homotopic mapping for contralateral sites. The most dorsal site is that shown in the photomicrograph in (D). AC, anterior commissure; CA, caudate; IC, internal capsule; OC, optic chiasm; SI, substantia innominata; V3, third ventricle. (D) Photomicrograph showing choline acetyltransferase–positive (ChAT+) neurons (dark spots) surrounding a probe tip site (top); this illustration was selected because the relatively superficial location of the tip in the substantia innominata allows clear visualization of ChAT+ neurons.