Sciatic Nerve Stimulation Does Not Increase Endogenous Adenosine Production in Sensory-Motor Cortex

Adenosine participates in the coupling of cerebral blood flow to oxygen consumption in the brain during such stimuli as hypoxia, ischemia, and seizures. It has been suggested that it also participates in the regulation of cerebral blood flow during somatosensory stimulation, a condition during which cerebral blood flow and oxygen consumption appear to be uncoupled. Interstitial adenosine was estimated by the microdialysis technique and cerebral blood flow was measured by hydrogen clearance in the hindlimb sensory-motor cortex during sciatic nerve stimulation. Cerebral blood flow increased from 102 to 188 ml min⁻¹ 100 g⁻¹ (p < 0.001) in the cortex contralateral to the stimulated leg without an associated increase in interstitial adenosine (baseline 0.624 μM, stimulation 0.583 μM). Infusion of the adenosine antagonist 8-sulfophenyltheophylline failed to block an increase in cerebral blood flow during central sciatic nerve stimulation, but decreased basal cerebral blood flow (69 ml min⁻¹ 100 g⁻¹). These results suggest that adenosine does not mediate changes in cerebral blood flow during somatosensory stimulation, but may participate in the regulation of cerebral blood flow in the basal state.