Specific T-type calcium channel isoforms are associated with distinct burst phenotypes in deep cerebellar nuclear neurons

T-type calcium channels are thought to transform neuronal output to a burst mode by generating low voltage-activated (LVA) calcium currents and rebound burst discharge. In this study we assess the expression pattern of the three different T-type channel isoforms ([Ca.sub.v]3.1, [Ca.sub.v]3.2, and [Ca.sub.v]3.3) in cerebellar neurons and focus on their potential role in generating LVA spikes and rebound discharge in deep cerebellar nuclear (DCN) neurons. We detected expression of one or more Car3 channel isoforms in a wide range of cerebellar neurons and selective expression of different isoforms in DCN cells. We further identify two classes of large-diameter DCN neurons that exhibit either a strong or weak capability for rebound discharge, despite the ability to generate LVA spikes when calcium currents are pharmacologically isolated. By correlating the [Ca.sub.v]3 channel expression pattern with the electrophysiological profile of identified DCN cells, we show that [Ca.sub.v]3.1 channels are expressed in isolation in DCN-burst cells, whereas [Ca.sub.v]3.3 is expressed in DCN-weak burst cells. [Ca.sub.v]3.1-expressing DCN cells correspond to excitatory or GABAergic neurons, whereas [Ca.sub.v]3.3-expressing cells are non-GABAergic. The [Ca.sub.v]3 class of LVA calcium channels is thus expressed in specific combinations in a wide range of cerebellar neurons but contributes to rebound burst discharge in only a select number of cell classes. Purkinje cells | cerebellum | rebound discharge