Rapid turnover of glycogen in memory formation.
The influence of noradrenaline acting at α(2)-AR and β(2)-ARs on the turnover of glycogen after learning has been investigated. The role of glycogen turnover in memory formation was examined using weakly-reinforced, single trial bead discrimination training in day-old domestic chickens. This study follows our previous work that focused on the need for glycogen breakdown (glycogenolysis) during learning. Inhibition of glycogenolysis by 1,4-dideoxy-1,4-imino-D-arabinitol (DAB) prevented the consolidation of strongly-reinforced learning and inhibited memory. The action of DAB could be prevented by stimulating glycogenolysis with the selective β(2)-AR agonist, zinterol. Stimulation of α(2)-ARs has been shown to lead to an increase in the turnover and synthesis of glycogen. In the present study, we examined the effect of inhibition of α(2)-AR stimulated glycogen turnover (measured as(14)C-glucose incorporation into glycogen) on the ability of zinterol to promote the consolidation of weakly reinforced memory. In astrocytes, the selective α(2)-AR agonist clonidine stimulated (14)C-glucose incorporation into glycogen in chick astrocytes and this was inhibited by the selective α(2)-AR antagonist, ARC239. The critical importance of the timing of ARC239 injection relative to training and intracerebral administration of zinterol was examined. It is concluded that our data provides evidence for a readily accessible labile pool of glycogen in brain astrocytes. If glycogen synthesis is inhibited, the can be depleted within 10 min, thus preventing zinterol from promoting consolidation.
Monash Institute of Pharmaceutical Sciences, Parkville, VIC 3052, Australia. marie.gibbs@monash.edu
Marie E
ME
Gibbs
Dana S
DS
Hutchinson
D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000378:metabolism; D002478:Cells, Cultured; D002642:Chick Embryo; D002645:Chickens; D003000:Clonidine / Q000494:pharmacology; D004983:Ethanolamines / Q000494:pharmacology; D006003:Glycogen / Q000378:metabolism*; D007546:Isoquinolines / Q000494:pharmacology; D008297:Male; D008568:Memory / Q000187:drug effects; D010879:Piperazines / Q000494:pharmacology
D000318:Adrenergic beta-Agonists; D004983:Ethanolamines; D007546:Isoquinolines; D010879:Piperazines; C002904:zinterol; D006003:Glycogen; C032994:AR-C239; D003000:Clonidine