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

Abstract

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_v3.1, Ca_v3.2, and Ca_v3.3) 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 Ca_v3 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_v3 channel expression pattern with the electrophysiological profile of identified DCN cells, we show that Ca_v3.1 channels are expressed in isolation in DCN-burst cells, whereas Ca_v3.3 is expressed in DCN-weak burst cells. Ca_v3.1-expressing DCN cells correspond to excitatory or GABAergic neurons, whereas Ca_v3.3-expressing cells are non-GABAergic. The Ca_v3 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.