Astrocyte membranes are highly permeable to K+ ions, leading to a hyperpolarized resting membrane potential and low input membrane resistance. The main player in mediating these properties is the Kir4.1 inward rectifying K+ channel [1, 2]. Without Kir4.1, astrocytes lack their signature K+ currents, which are sensitive to K+ blockers such as Ba2+ [3, 4]. The Kir4.1 channels are expressed throughout the brain, but are found in the highest concentrations in the olfactory bulb, cerebellum, brain stem, spinal cord and midbrain. While Kir4.1 is not expressed in neurons, it is expressed in a variety of CNS glia, including oligodendrocytes, and astrocytes. Protoplasmic astrocytes within the grey matter have higher Kir4.1 expression than fibrous astrocytes within the white matter [2, 5]. The expression of Kir4.1 increases with age, particularly within the first 10 days postnatally. This increase is associated with both an increase of the inward current in developing astrocytes and a shift away from oligodedroglial expression of Kir4.1 [6, 3].