title: Astrocytes modulate a postsynaptic NMDA-GABAA-receptor crosstalk in hypothalamic neurosecretory neurons.
abstract: A dynamic balance between the excitatory and inhibitory neurotransmitters glutamate and GABA is critical for maintaining proper neuronal activity in the brain. This balance is partly achieved via presynaptic interactions between glutamatergic and GABA(A)ergic synapses converging into the same targets. Here, we show that in hypothalamic magnocellular neurosecretory neurons (MNCs), a direct crosstalk between postsynaptic NMDA receptors (NMDARs) and GABA(A) receptors (GABA(A)Rs) contributes to the excitatory/inhibitory balance in this system. We found that activation of NMDARs by endogenous glutamate levels controlled by astrocyte glutamate transporters, evokes a transient and reversible potentiation of postsynaptic GABA(A)Rs. This inter-receptor crosstalk is calcium-dependent and involves a kinase-dependent phosphorylation mechanism, but does not require nitric oxide as an intermediary signal. Finally, we found the NMDAR-GABA(A)R crosstalk to be blunted in rats with heart failure, a pathological condition in which the hypothalamic glutamate-GABA balance is tipped toward an excitatory predominance. Together, our findings support a novel form of glutamate-GABA interactions in MNCs, which involves crosstalk between NMDA and GABA(A) postsynaptic receptors, whose strength is controlled by the activity of local astrocytes. We propose this inter-receptor crosstalk to act as a compensatory, counterbalancing mechanism to dampen glutamate-mediated overexcitation. Finally, we propose that an uncoupling between NMDARs and GABA(A)Rs may contribute to exacerbated neuronal activity and, consequently, sympathohumoral activation in such disease conditions as heart failure.
authors.affiliation: Department of Physiology, Georgia Health Sciences University, Augusta, Georgia 30912, USA.
authors.forename: Evgeniy S
authors.initials: ES
authors.lastname: Potapenko
authors.forename: Vinicia C
authors.initials: VC
authors.lastname: Biancardi
authors.forename: Yiqiang
authors.initials: Y
authors.lastname: Zhou
authors.forename: Javier E
authors.initials: JE
authors.lastname: Stern
mesh_terms: D000818:Animals; D001253:Astrocytes / Q000187:drug effects / Q000502:physiology*; D020013:Calcium Signaling / Q000502:physiology; D055724:Electrophysiological Phenomena; D027342:Excitatory Amino Acid Transporter 2 / Q000235:genetics / Q000502:physiology; D018755:GABA Agonists / Q000494:pharmacology; D005971:Glutamates / Q000502:physiology; D006333:Heart Failure / Q000503:physiopathology; D007031:Hypothalamus / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D008297:Male; D009118:Muscimol / Q000494:pharmacology; D009474:Neurons / Q000187:drug effects / Q000502:physiology*; D009490:Neurosecretory Systems / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D009569:Nitric Oxide / Q000502:physiology; D018408:Patch-Clamp Techniques; D011494:Protein Kinases / Q000502:physiology; D051381:Rats; D017208:Rats, Wistar; D020239:Receptor Cross-Talk / Q000187:drug effects / Q000502:physiology*; D011963:Receptors, GABA-A / Q000187:drug effects / Q000502:physiology*; D016194:Receptors, N-Methyl-D-Aspartate / Q000187:drug effects / Q000502:physiology*; D013569:Synapses / Q000502:physiology
chemical_list: D027342:Excitatory Amino Acid Transporter 2; D018755:GABA Agonists; D005971:Glutamates; D011963:Receptors, GABA-A; D016194:Receptors, N-Methyl-D-Aspartate; C493395:Slc1a2 protein, rat; D009118:Muscimol; D009569:Nitric Oxide; D011494:Protein Kinases