Lactate in the brain of the freely moving rat: voltammetric monitoring of the changes related to the sleep-wake states.
Cortical lactate was monitored voltammetrically in freely moving rats equipped with polygraphic electrodes. Differential normal pulse voltammetric measurements were carried out using a lactate biosensor coated with lactate oxidase and cellulose acetate. Changes occurring in lactate level were in keeping with sleep-wake states. During slow wave sleep (SWS), the lactate level decreased significantly (-16.2%) vs. the spontaneous waking state (W) referenced to as 100%. During paradoxical sleep (PS), and still vs. W, it remained low (-9.0%) but this variation was not statistically significant. However, when this PS change was compared to the SWS variation, a significant increase in lactate level was then revealed (+8.5%). Finally, during the active waking (aW) triggered by a water puff stress, lactate level rose significantly in accordance with the animal activity (+53% compared to W). Long-term monitoring also allowed the determination of a circadian component in lactate production, the lowest and highest values being monitored during light and dark periods, respectively. The acrophasis of the circadian change occurred during the dark period, about 3 h after the light-off (+89%). It is suggested that during wakefulness astrocyte metabolism allows the transformation of the blood-borne glucose into lactate. The increase in this substrate observed during PS may fulfil the oxidative phosphorylation in order to supply the important ATP need of PS.
Shram
Nataliya
N
INSERM Unit 480, Claude Bernard University, 8 av. Rockefeller, 69373 Lyon cedex 08, France.
Netchiporouk
Larissa
L
Cespuglio
Raymond
R
D000818:Animals; D015374:Biosensing Techniques; D002540:Cerebral Cortex / Q000378:metabolism*; D002940:Circadian Rhythm / Q000502:physiology; D003624:Darkness; D004734:Energy Metabolism / Q000502:physiology*; D005110:Extracellular Space / Q000378:metabolism*; D019344:Lactic Acid / Q000378:metabolism*; D008297:Male; D009068:Movement / Q000502:physiology; D009474:Neurons / Q000378:metabolism*; D010085:Oxidative Phosphorylation; D010775:Photic Stimulation; D051381:Rats; D017208:Rats, Wistar; D012890:Sleep / Q000502:physiology*; D013312:Stress, Physiological / Q000378:metabolism / Q000503:physiopathology; D014851:Wakefulness / Q000502:physiology*
D019344:Lactic Acid