Extracellular adenosine in the human brain during sleep and sleep deprivation: An in vivo microdialysis study

Study Objectives: To examine the pattern of extracellular adenosine in the human brain during sleep deprivation, sleep, and normal wake. Design: Following recovery from implantation of clinical depth electrodes, epilepsy patients remained awake for 40 continuous hours, followed by a recovery sleep episode. Setting: Neurology ward at UCLA Medical Center. Patients or Participants: Seven male epilepsy patients undergoing depth electrode localization of pharmacologically refractory seizures. Interventions: All subjects were implanted with depth electrodes, a subset of which were customized to contain microdialysis probes. Microdialysis samples were collected during normal sleep, sleep deprivation, and recovery sleep from human amygdalae (n=8), hippocampus (n=1), and cortex (n=1). Measurements and Results: In none of the probes did we observe an increase in extracellular adenosine during the sleep deprivation. There was a significant, though very small, diurnal oscillation (2.5%) in 5 of the 8 amygdalae. There was no effect of epileptogenicity on the pattern of extracellular adenosine. Conclusions: Our observations, along with those in animal studies, indicate that the role of extracellular adenosine in regulating sleep pressure is not a global brain phenomenon but is likely limited to specific basal forebrain areas. Thus, if energy homeostasis is a function of sleep, an increased rate of adenosine release into the extracellular milieu of the amygdala, cortex, or hippocampus is unlikely to be a marker of such a process