title: Developmental up-regulation of KCC2 in the absence of GABAergic and glutamatergic transmission.
abstract: Postsynaptic gamma-aminobutyric acid (GABA)A-mediated responses switch from depolarizing to hyperpolarizing during postnatal development of the rodent hippocampus. This is attributable to a decrease in the concentration of intracellular chloride set by the expression of the neuron-specific K+-Cl- co-transporter, KCC2. A recent in vitro study [Ganguly et al. (2001) Cell, 105, 521-532] showed that KCC2 expression may be under the trophic control of GABAA receptor-mediated transmission. Here we have studied the developmental expression of KCC2 protein in mouse hippocampal dissociated cultures as well as organotypic cultures. A low somatic expression level was found in neurons prior to the formation of the first synapses, as detected by synaptophysin immunoreactivity. Thereafter, KCC2 expression was strongly up-regulated during neuronal maturation. The developmental up-regulation of KCC2 expression was not altered by a chronic application (throughout the culturing period; 2-15 days in vitro) of the action-potential blocker TTX or the N-methyl-d-aspartate (NMDA) and non-NMDA antagonists APV and NBQX. Blockade of GABAA-mediated transmission with picrotoxin did not affect the expression levels of KCC2 protein either. These data show that neither neuronal spiking nor ionotropic glutamatergic and GABAergic transmission are required for the developmental expression of KCC2 in mouse hippocampal neurons in vitro.
authors.affiliation: Institute of Biotechnology, FIN-00014, University of Helsinki, Finland.
authors.forename: Anastasia
authors.initials: A
authors.lastname: Ludwig
authors.forename: Hong
authors.initials: H
authors.lastname: Li
authors.forename: Mart
authors.initials: M
authors.lastname: Saarma
authors.forename: Kai
authors.initials: K
authors.lastname: Kaila
authors.forename: Claudio
authors.initials: C
authors.lastname: Rivera
mesh_terms: D000200:Action Potentials / Q000187:drug effects / Q000502:physiology; D000818:Animals; D000831:Animals, Newborn; D000918:Antibody Specificity; D002454:Cell Differentiation / Q000187:drug effects / Q000502:physiology; D002478:Cells, Cultured; D018691:Excitatory Amino Acid Antagonists / Q000494:pharmacology; D005333:Fetus; D018756:GABA Antagonists / Q000494:pharmacology; D018698:Glutamic Acid / Q000378:metabolism; D006624:Hippocampus / Q000196:embryology / Q000254:growth & development / Q000378:metabolism*; D007150:Immunohistochemistry; D051379:Mice; D008869:Microtubule-Associated Proteins / Q000378:metabolism; D009474:Neurons / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D009924:Organ Culture Techniques; D011963:Receptors, GABA-A / Q000378:metabolism*; D026941:Sodium Channel Blockers / Q000494:pharmacology; D027981:Symporters / Q000378:metabolism*; D013569:Synapses / Q000187:drug effects / Q000378:metabolism; D009435:Synaptic Transmission / Q000187:drug effects / Q000502:physiology; D016708:Synaptophysin / Q000378:metabolism; D015854:Up-Regulation / Q000502:physiology*; D005680:gamma-Aminobutyric Acid / Q000378:metabolism; D000096922:K Cl- Cotransporters
chemical_list: D018691:Excitatory Amino Acid Antagonists; D018756:GABA Antagonists; D018698:Glutamic Acid; D008869:Microtubule-Associated Proteins; D011963:Receptors, GABA-A; D026941:Sodium Channel Blockers; D027981:Symporters; D016708:Synaptophysin; D005680:gamma-Aminobutyric Acid; D000096922:K Cl- Cotransporters