State-dependence of climbing fiber-driven calcium transients in Purkinje cells

The recently described bi-stability of Purkinje cells and the state-dependence of the complex spike waveform suggest that calcium currents may play a pivotal role in both the complex spike waveform and the state of the membrane voltage. Here we used Ca2+ imaging to record the changes in intracellular [Ca2+] that are elicited by either spontaneous or climbing fiber-evoked activity in rat Purkinje cells. We show that a continuous somatic Ca2+ influx occurs during an "UP" state. Furthermore Ca2+ transients that are evoked by climbing fiber stimulation are state-dependent. Somatic transients are smaller following an "UP" state, while dendritic transients are smaller following a "DOWN" state. The state-dependence of these signals should affect the intrinsic firing of Purkinje cells as well as plastic processes that modulate synaptic strength.