Lactate in the brain of the freely moving rat: voltammetric monitoring of the changes related to the sleep-wake states

• Published in: The European journal of neuroscience 2002-08, Vol.16 (3), p.461-466
• Main Authors: Shram, Nataliya, Netchiporouk, Larissa, Cespuglio, Raymond
• Format: Article
• Language: English
• Subjects: Animals; Biosensing Techniques; biosensor; Cerebral Cortex - metabolism; Circadian Rhythm - physiology; Darkness; Energy Metabolism - physiology; Extracellular Space - metabolism; lactate; Lactic Acid - metabolism; Male; Movement - physiology; Neurons - metabolism; Oxidative Phosphorylation; Photic Stimulation; rat; Rats; Rats, Wistar; Sleep - physiology; sleep-wake cycle; Stress, Physiological - metabolism; Stress, Physiological - physiopathology; voltammetry; Wakefulness - physiology
• ISSN: 0953-816X; 1460-9568
• DOI: 10.1046/j.1460-9568.2002.02081.x

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.