Differential expression of three classes of voltage-gated Ca 2+ channels during maturation of the rat cerebellum in vitro

Abstract

Voltage-gated Ca 2+ channels provide a mode of Ca 2+ 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 Ca 2+ channels (α1A, α1B and α1E) during development, in cultures established from prenatal rat cerebellar cortex. Ca 2+ channel transcript levels were standardized to a constitutive marker (cyclophilin). For all three classes of Ca 2+ 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) Ca 2+ channels during neuronal maturation (10–21 days in vitro), but dramatically suppressed transcript levels for the α1A (P-type) Ca 2+ 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 Ca 2+ for α1E but not for α1A. For α1B, transcript levels depended on extracellular Ca 2+ only for increased K + as the depolarizing stimulus, but not for TEA. These results suggest that levels of Ca 2+ channel transcripts in rat cerebellum are developmentally regulated in vitro and can be influenced differentially by transmembrane signaling via chronic depolarization and Ca 2+ entry. Dynamic regulation of Ca 2+ channel expression may be relevant to the different functional roles of Ca 2+ channels and their regional localization within neurons.