T-Type Ca2+ Current Properties Are Not Modified by Ca2+ Channel beta  Subunit Depletion in Nodosus Ganglion Neurons

At the molecular level, our knowledge of the low voltage-activated Ca2+ channel (T-type) has made little progress. Using an antisense strategy, we investigated the possibility that the T-type channels have a structure similar to high voltage-activated Ca2+ channels. It is assumed that high voltage-activated channels are made of at least three components: a pore forming alpha1 subunit combined with a cytoplasmic modulatory beta subunit and a primarily extracellular alpha2delta subunit. We have examined the effect of transfecting cranial primary sensory neurons with generic anti-beta antisense oligonucleotides. We show that in this cell type, blocking expression of all known beta gene products does not affect T-type current, although it greatly decreases the current amplitude of high voltage-activated channels and modifies their voltage dependence. This suggests that beta subunits are likely not constitutive of T-type Ca2+ channels in this cell type.