Extracellular adenosine in the human brain during sleep and sleep deprivation: an in vivo microdialysis study.
Level 4 - case-series / case-control
Case series of patients undergoing invasive intracranial monitoring
PubMed 16676778 · doi:10.1093/sleep/29.4.455
What was done
Seven male patients with medically refractory epilepsy undergoing intracranial depth electrode monitoring were studied during normal sleep, 40 hours of continuous sleep deprivation, and recovery sleep. In vivo microdialysis probes integrated into depth electrodes collected extracellular fluid from the amygdala (n = 8 probes), hippocampus (n = 1), and cortex (n = 1) to measure adenosine levels across sleep-wake states.
What was found
No probe demonstrated an increase in extracellular adenosine during sleep deprivation. A statistically significant but small diurnal oscillation (2.5%) occurred in 5 of the 8 amygdala probes. Epileptogenicity showed no effect on extracellular adenosine patterns.
Why it matters
These findings suggest that extracellular adenosine accumulation during prolonged wakefulness is not a widespread, whole-brain marker of sleep homeostasis, but is likely restricted to specific brain regions such as the basal forebrain.
Limits
The study evaluated a very small sample (n = 7) consisting entirely of male epilepsy patients on clinical monitoring units. Probe locations were clinically dictated, leaving key sleep-regulating areas like the basal forebrain unmeasured and resulting in only single probes for the cortex and hippocampus.
Cited by
- context Adenosine accumulates in the brain and body relative to the number of hours spent awake.