Astrocyte-interneuron interplay tunes neuronal excitability by enhancing the slow Ca^2 + -activated K⁺ current

Neurons have the unique ability to integrate synaptic information by modulating the function of the voltage-gated membrane ion channels, which govern their excitability. Astrocytes play active roles in synaptic function, from synapse formation and maturation to plasticity processes. However, it remains elusive whether astrocytes can impact the neuronal activity by regulating membrane ionic conductances that control the intrinsic firing properties. Here, we found that astrocytes enhance the slow Ca²⁺-activated K⁺ current (sIAHP) in CA1 hippocampal pyramidal neurons through the release of adenosine. Remarkably, our results indicate that interneuron activity plays a crucial role in this astrocyte-mediated modulation of sIAHP. Specifically, optogenetically stimulated hippocampal interneurons were found to evoke coordinated signaling between astrocytes and pyramidal neurons, relying on the activation of GABA_B and adenosine A1 receptors. In addition, the selective genetic ablation of GABA_B receptors in CA1 astrocytes prevented the potentiation of sIAHP and spike frequency adaptation in pyramidal cells following interneuron activation. Therefore, our data reveal the capability of astrocytes to modulate the intrinsic membrane properties that dictate neuronal firing rate, which in turn governs hippocampal network activity.