Ouabain block of the Na⁺/K⁺ pump switches Purkinje cell activity out of the trimodal firing pattern and into a continuous burst mode.

<p>Panel <i>A</i> shows a whole cell patch clamp recording from a Purkinje cell (with 10 µM bicuculline already present to block GABAergic inputs) following the application of 2.5 µM ouabain. The arrow denotes the time at which we feel that ouabain starts to modify Purkinje cell firing. Panels <i>B</i>, <i>C</i>, <i>D</i>, and <i>E</i> correspond to the labelled parts of panel <i>A</i>. Panels <i>F</i>, <i>G</i>, <i>H</i> and <i>I</i> show individual bursts from <i>B</i>, <i>D</i>, <i>D</i> and <i>E</i> respectively. The initial firing mode, before any Na⁺/K⁺ pump block, is trimodal (panel <i>B</i>). With time, as Na⁺/K⁺ pumps become blocked, the trimodal pattern's quiescent periods get shorter until they are eventually abolished and the cell fires continuously (panel <i>A</i>). Over this same period the length of the trimodal pattern's tonic mode also decreases, ceding to an increasing propensity to burst (compare panels <i>B</i> and <i>C</i>). Indeed, by the time of continuous firing (panel <i>D</i>) there is only bursting and no tonic fraction at all. After a period, this continuous bursting acquires a gradient of depolarization (Panel <i>A</i>). As it depolarizes, the number of spikes per burst steadily decreases (<i>F</i>, <i>G</i>, <i>H</i>) until the soma enters depolarization block and there are none. In this case, the only deflections observed are those of the Ca²⁺ spikes that have travelled into the soma from the dendritic arborisation (<i>E</i>, <i>I</i>). <i>Panel A scaling is encoded in the first scale bar (50 mV, 50 s). The scaling of panels B, C, D and E is encoded in the second scale bar (50 mV, 3 s). The scaling of panels F, G, H and I is encoded in the third scale bar (50 mV, 100 ms)</i>.