Differential expression of three classes of voltage-gated Ca²⁺ channels during maturation of the rat cerebellum in vitro

Voltage-gated Ca²⁺ channels provide a mode of Ca²⁺ influx that is essential for intracellular signaling in many cells. Semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) was used to assess the relative amounts of mRNAs encoding three classes of Ca²⁺ channels (α1A, α1B and α1E) during development, in cultures established from prenatal rat cerebellar cortex. Ca²⁺ channel transcript levels were standardized to a constitutive marker (cyclophilin). For all three classes of Ca²⁺ channels, transcript levels were highest at early stages (4-10 days in vitro) and declined with age. This developmental pattern was differentially regulated by a depolarizing agent, tetraethylammonium chloride (TEA, 1 mM). Chronic depolarization yielded a significant elevation in transcript levels for α1B (N-type) and α1E (R-type) Ca²⁺ channels during neuronal maturation (10-21 days in vitro), but dramatically suppressed transcript levels for the α1A (P-type) Ca²⁺ channel at all stages of development. The effects of TEA on α1A, α1B and α1E transcript levels were mimicked by increasing external K⁺ (from 5 to 10 mM). The regulatory effects of depolarization on transcript levels were dependent on extracellular Ca²⁺ for α1E but not for α1A. For α1B, transcript levels depended on extracellular Ca²⁺ only for increased K⁺ as the depolarizing stimulus, but not for TEA. These results suggest that levels of Ca²⁺ channel transcripts in rat cerebellum are developmentally regulated in vitro and can be influenced differentially by transmembrane signaling via chronic depolarization and Ca²⁺ entry. Dynamic regulation of Ca²⁺ channel expression may be relevant to the different functional roles of Ca²⁺ channels and their regional localization within neurons.