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 (alpha 1A, alpha 1B and alpha 1E) 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 alpha 1B (N-type) and alpha 1E (R-type) Ca2+ channels during neuronal maturation (10-21 days in vitro), but dramatically suppressed transcript levels for the alpha 1A (P-type) Ca2+ channel at all stages of development. The effects of TEA on alpha 1A, alpha 1B and alpha 1E 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 alpha 1E but not for alpha 1A. For alpha 1B, 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. (C) 1999 Elsevier Science B.V. All rights reserved.