title: Influence of age on BDNF modulation of hippocampal synaptic transmission: interplay with adenosine A2A receptors.
abstract: We previously reported that adenosine, through A(2A) receptor activation, potentiates synaptic actions of brain-derived neurotrophic factor (BDNF) in the hippocampus of infant (3-4 weeks) rats. Since A(2A)-receptor-mediated actions are more evident in old than in young rats and since the therapeutic potential for BDNF-based strategies is greater in old subjects, we now evaluated synaptic actions of BDNF and the levels of TrkB receptors and of adenosine A(2A) receptors in the hippocampus of three groups of adult rats: young adults (10-16 weeks), old adults (36-38 weeks), and aged (70-80 weeks), as well as in one group of infant (3-4 weeks) rats. BDNF (20 ng/ml) enhances field excitatory postsynaptic potentials recorded from the hippocampus of young adults and aged rats, an action triggered by adenosine A(2A) receptor activation, since it was blocked by the A(2A) receptor antagonist, ZM 241385. In the other groups of animals BDNF (20 ng/ml) was virtually devoid of action on synaptic transmission. Western blot analysis of receptor density shows decreased amounts of TrkB receptors in old adults and aged rats, whereas A(2A) receptor levels assayed by ligand binding are enhanced in the hippocampus of old adults and aged rats. It is concluded that age-related changes in the density of TrkB receptors and of adenosine A(2A) receptors may be responsible for a nonmonotonous variation of BDNF actions on synaptic transmission in the hippocampus.
authors.affiliation: Institute of Pharmacology and Neurosciences, Faculty of Medicine, University of Lisbon, Lisbon, Portugal.
authors.forename: Maria J
authors.initials: MJ
authors.lastname: Diógenes
authors.forename: Natália
authors.initials: N
authors.lastname: Assaife-Lopes
authors.forename: António
authors.initials: A
authors.lastname: Pinto-Duarte
authors.forename: Joaquim A
authors.initials: JA
authors.lastname: Ribeiro
authors.forename: Ana M
authors.initials: AM
authors.lastname: Sebastião
mesh_terms: D000241:Adenosine / Q000378:metabolism; D058908:Adenosine A2 Receptor Agonists; D000375:Aging / Q000502:physiology*; D000818:Animals; D001667:Binding, Competitive / Q000502:physiology; D019208:Brain-Derived Neurotrophic Factor / Q000378:metabolism* / Q000494:pharmacology; D015536:Down-Regulation / Q000187:drug effects / Q000502:physiology; D019706:Excitatory Postsynaptic Potentials / Q000187:drug effects / Q000502:physiology; D006624:Hippocampus / Q000187:drug effects / Q000254:growth & development* / Q000378:metabolism*; D008297:Male; D009434:Neural Pathways / Q000187:drug effects / Q000254:growth & development / Q000378:metabolism; D009924:Organ Culture Techniques; D017729:Presynaptic Terminals / Q000378:metabolism; D011869:Radioligand Assay; D051381:Rats; D017208:Rats, Wistar; D043705:Receptor, Adenosine A2A / Q000378:metabolism*; D020813:Receptor, trkB / Q000819:agonists / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology*; D015854:Up-Regulation / Q000187:drug effects / Q000502:physiology
chemical_list: D058908:Adenosine A2 Receptor Agonists; D019208:Brain-Derived Neurotrophic Factor; D043705:Receptor, Adenosine A2A; D020813:Receptor, trkB; D000241:Adenosine