Unveiling Ketamine's Influence on Astrocytic Kir4.1 Channels Through Multimodal Analysis: Confocal Microscopy,...

Understanding the elusive mechanisms responsible for the therapeutic efficacy of ketamine in major depressive disorder (MDD) is crucial. Astrocytes play a vital role in regulating extracellular potassium concentration ([K⁺]_o), which is essential for maintaining proper neuronal excitability and overall brain function. Dysregulation of [K⁺]_o can lead to significant changes in neuronal activity, potentially contributing to the pathophysiology of various neurological and psychiatric conditions, including depression. To this end, we conducted a multifaceted investigation to elucidate the effects of ketamine on the inwardly rectifying K⁺ channel Kir4.1, which is critical for neuronal excitability and K⁺ homeostasis. Using cultured rat cortical astrocytes expressing fluorescently labeled Kir4.1 (Kir4.1-EGFP), we followed the dynamics of Kir4.1-EGFP vesicles after ketamine exposure. In addition, using live cell immunolabeling and patch-clamp assays in cultured mouse astrocytes, we investigated the effects of ketamine on Kir4.1 surface density and voltage-activated currents, similar to Ba²⁺ inhibition. This comprehensive methodological approach sheds light on the modulation of Kir4.1 dynamics by ketamine and thus provides valuable insights into its therapeutic mechanisms in MDD.