Beta2- and beta3-adrenoceptors activate glucose uptake in chick astrocytes by distinct mechanisms: a mechanism for memory enhancement?
Isoprenaline, acting at beta-adrenoceptors (ARs), enhances memory formation in single trial discriminated avoidance learning in day-old chicks by mechanisms involving alterations in glucose and glycogen metabolism. Earlier studies of memory consolidation in chicks indicated that beta3-ARs enhanced memory by increasing glucose uptake, whereas beta2-ARs enhance memory by increasing glycogenolysis. This study examines the ability of beta-ARs to increase glucose uptake in chick forebrain astrocytes. The beta-AR agonist isoprenaline increased glucose uptake in a concentration-dependent manner, as did insulin. Glucose uptake was increased by the beta2-AR agonist zinterol and the beta3-AR agonist CL316243, but not by the beta1-AR agonist RO363. In chick astrocytes, reverse transcription-polymerase chain reaction studies showed that beta1-, beta2-, and beta3-AR mRNA were present, whereas radioligand-binding studies showed the presence of only beta2- and beta3-ARs. beta-AR or insulin-mediated glucose uptake was inhibited by phosphatidylinositol-3 kinase and protein kinase C inhibitors, suggesting a possible interaction between the beta-AR and insulin pathways. However beta2- and beta3-ARs increase glucose uptake by two different mechanisms: beta2-ARs via a Gs-cAMP-protein kinase A-dependent pathway, while beta3-ARs via interactions with Gi. These results indicate that activation of beta2- and beta3-ARs causes glucose uptake in chick astrocytes by distinct mechanisms, which may be relevant for memory enhancement.
Hutchinson
Dana S
DS
Department of Pharmacology, Monash University, Victoria, Australia. dana.hutchinson@med.monash.edu.au
Summers
Roger J
RJ
Gibbs
Marie E
ME
D058666:Adrenergic beta-2 Receptor Agonists; D058667:Adrenergic beta-3 Receptor Agonists; D000318:Adrenergic beta-Agonists / Q000494:pharmacology; D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000378:metabolism*; D001921:Brain / Q000166:cytology / Q000378:metabolism*; D002478:Cells, Cultured; D002642:Chick Embryo; D004149:Dioxoles / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D004983:Ethanolamines / Q000494:pharmacology; D019206:GTP-Binding Protein alpha Subunits, Gi-Go / Q000187:drug effects / Q000378:metabolism; D019205:GTP-Binding Protein alpha Subunits, Gs / Q000187:drug effects / Q000378:metabolism; D005947:Glucose / Q000378:metabolism* / Q000493:pharmacokinetics; D007328:Insulin / Q000378:metabolism / Q000494:pharmacology; D007545:Isoproterenol / Q000494:pharmacology; D008568:Memory / Q000187:drug effects / Q000502:physiology*; D019869:Phosphatidylinositol 3-Kinases / Q000378:metabolism; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism; D012333:RNA, Messenger / Q000187:drug effects / Q000378:metabolism; D018343:Receptors, Adrenergic, beta-2 / Q000235:genetics / Q000378:metabolism*; D022702:Receptors, Adrenergic, beta-3 / Q000235:genetics / Q000378:metabolism*; D015398:Signal Transduction / Q000187:drug effects / Q000502:physiology
D058666:Adrenergic beta-2 Receptor Agonists; D058667:Adrenergic beta-3 Receptor Agonists; D000318:Adrenergic beta-Agonists; D004149:Dioxoles; D004791:Enzyme Inhibitors; D004983:Ethanolamines; D019206:GTP-Binding Protein alpha Subunits, Gi-Go; D019205:GTP-Binding Protein alpha Subunits, Gs; D005947:Glucose; D007328:Insulin; D007545:Isoproterenol; D019869:Phosphatidylinositol 3-Kinases; D000081082:Phosphoinositide-3 Kinase Inhibitors; D011493:Protein Kinase C; D012333:RNA, Messenger; D018343:Receptors, Adrenergic, beta-2; D022702:Receptors, Adrenergic, beta-3; C076126:disodium (R,R)-5-(2-((2-(3-chlorophenyl)-2-hydroxyethyl)-amino)propyl)-1,3-benzodioxole-2,3-dicarboxylate; C002904:zinterol