title: Lactate produced by glycogenolysis in astrocytes regulates memory processing.
abstract: When administered either systemically or centrally, glucose is a potent enhancer of memory processes. Measures of glucose levels in extracellular fluid in the rat hippocampus during memory tests reveal that these levels are dynamic, decreasing in response to memory tasks and loads; exogenous glucose blocks these decreases and enhances memory. The present experiments test the hypothesis that glucose enhancement of memory is mediated by glycogen storage and then metabolism to lactate in astrocytes, which provide lactate to neurons as an energy substrate. Sensitive bioprobes were used to measure brain glucose and lactate levels in 1-sec samples. Extracellular glucose decreased and lactate increased while rats performed a spatial working memory task. Intrahippocampal infusions of lactate enhanced memory in this task. In addition, pharmacological inhibition of astrocytic glycogenolysis impaired memory and this impairment was reversed by administration of lactate or glucose, both of which can provide lactate to neurons in the absence of glycogenolysis. Pharmacological block of the monocarboxylate transporter responsible for lactate uptake into neurons also impaired memory and this impairment was not reversed by either glucose or lactate. These findings support the view that astrocytes regulate memory formation by controlling the provision of lactate to support neuronal functions.
authors.affiliation: Neuroscience Program, University of Illinois at Urbana-Champaign, Champaign, Illinois, United States of America. lanewman@illinois.edu
authors.forename: Lori A
authors.initials: LA
authors.lastname: Newman
authors.forename: Donna L
authors.initials: DL
authors.lastname: Korol
authors.forename: Paul E
authors.initials: PE
authors.lastname: Gold
mesh_terms: D000818:Animals; D001089:Arabinose; D001253:Astrocytes / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000378:metabolism; D006003:Glycogen / Q000378:metabolism; D050261:Glycogenolysis / Q000187:drug effects; D050113:Imino Furanoses; D019344:Lactic Acid / Q000096:biosynthesis* / Q000378:metabolism; D008297:Male; D008568:Memory / Q000187:drug effects; D027501:Monocarboxylic Acid Transporters / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D051381:Rats; D017207:Rats, Sprague-Dawley; D013037:Spatial Behavior / Q000187:drug effects / Q000502:physiology; D013402:Sugar Alcohols / Q000494:pharmacology
chemical_list: D050113:Imino Furanoses; D027501:Monocarboxylic Acid Transporters; C091633:Slc16a7 protein, rat; D013402:Sugar Alcohols; C058137:1,4-dideoxy-1,4-iminoarabinitol; D019344:Lactic Acid; D006003:Glycogen; D001089:Arabinose; D005947:Glucose