Browsing by Author "Lemunao, Yordan"
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Item GABAergic Regulation of Astroglial Gliotransmission through Cx43 Hemichannels(2022) Jiménez, Ivanka; Reyes, Rachel; Lemunao, Yordan; Cárdenas, Kevin; Castro, Raimundo; Peña, Francisca; Lucero, Claudia; Prieto, Juan; Retamal, Mauricio; Orellana, Juan; Stehberg, JimmyGamma-Aminobutyric acid (GABA) is the primary inhibitory neurotransmitter in the brain. It is produced by interneurons and recycled by astrocytes. In neurons, GABA activates the influx of Cl- via the GABAA receptor or efflux or K+ via the GABAB receptor, inducing hyperpolarization and synaptic inhibition. In astrocytes, the activation of both GABAA and GABAB receptors induces an increase in intracellular Ca2+ and the release of glutamate and ATP. Connexin 43 (Cx43) hemichannels are among the main Ca2+-dependent cellular mechanisms for the astroglial release of glutamate and ATP. However, no study has evaluated the effect of GABA on astroglial Cx43 hemichannel activity and Cx43 hemichannel-mediated gliotransmission. Here we assessed the effects of GABA on Cx43 hemichannel activity in DI NCT1 rat astrocytes and hippocampal brain slices. We found that GABA induces a Ca2+-dependent increase in Cx43 hemichannel activity in astrocytes mediated by the GABAA receptor, as it was blunted by the GABAA receptor antagonist bicuculline but unaffected by GABAB receptor antagonist CGP55845. Moreover, GABA induced the Cx43 hemichannel-dependent release of glutamate and ATP, which was also prevented by bicuculline, but unaffected by CGP. Gliotransmission in response to GABA was also unaffected by pannexin 1 channel blockade. These results are discussed in terms of the possible role of astroglial Cx43 hemichannel-mediated glutamate and ATP release in regulating the excitatory/inhibitory balance in the brain and their possible contribution to psychiatric disorders.Publication The role of astrocytes in depression, its prevention and treatment by targeting astroglial gliotransmitter release(2024) Duarte, Yorley; Quintana, Daisy; Moraga-Amaro, Rodrigo; Dinamarca, Ivanka; Lemunao, Yordan; Cárdenas, Kevin; Bahamonde, Tamara; Barrientos, Tabita; Olivares, Pedro; Navas, Camila; Carvajal, Francisco J.; Santibáñez, Yessenia; Castro, Raimundo; Meza, María Paz; Jorquera, Ramón; Gómez, Gonzalo I.; Henke, Marina; Alarcón, Rodrigo; Gabriel, Laureen A.; Schiffmann, Susanne; Cerpa, Waldo; Retamal, Mauricio A.; Simon, Felipe; Linsambarth, Sergio; González Nilo, Fernando; Stehberg, JimmyThe role of ventral hippocampus (vHipp) astroglial gliotransmission in depression was studied using chronic restraint stress (CRS) and chronic unpredictable mild stress (CUMS) rodent models. CRS increased Cx43 hemichannel activity and extracellular glutamate levels in the vHipp and blocking astroglial Cx43 hemichannel-dependent gliotransmission during CRS prevented the development of depression and glutamate buildup. Moreover, the acute blockade of Cx43 hemichannels induced antidepressant effects in rats previously subjected to CRS or CUMS. This antidepressant effect was prevented by coinjection of glutamate and D-serine. Furthermore, Cx43 hemichannel blockade decreased postsynaptic NMDAR currents in vHipp slices in a glutamate and D-serine-dependent manner. Notably, chronic microinfusion of glutamate and D-serine, L-serine, or the NMDAR agonist NMDA, into the vHipp induced depressive-like symptoms in nonstressed rats. We also identified a small molecule, cacotheline, which blocks Cx43 hemichannels and its systemic administration induced rapid antidepressant effects, preventing stress-induced increases in astroglial Cx43 hemichannel activity and extracellular glutamate in the vHipp, without sedative or locomotor side effects. In conclusion, chronic stress increases Cx43 hemichannel-dependent release of glutamate and D-/L-serine from astrocytes in the vHipp, overactivating postsynaptic NMDARs and triggering depressive-like symptoms. This study highlights the critical role of astroglial gliotransmitter release in chronic stress-induced depression and suggests it can be used as a target for the prevention and treatment of depression.