Figure 7.

Depolarization blocked the expression of cbln1 and cbln3 mRNA in developing granule cells. A, Schematic diagram indicating the timing of the drug treatment. Cerebellar granule cells were maintained in normal K⁺ (5 mm; control) or high-K⁺ (30 mm) media from 0 DIV through to 14 DIV. Nimodipine (50 μm), FK520 (0.5 μg/ml), or d-AP5 (100 μm) was added for the last 3 d. B, Effects of high K⁺ and various blockers on the developmental expression of various genes. Expression levels of mRNAs for cbln1, cbln3, NR2C, GABAα6, BDNF, and GAPDH were determined using semiquantitative PCR. C, Quantitative analysis of data shown in B. The band intensities of cbln1, cbln3, and GABAα6 transcripts were normalized to those of GAPDH, and the value of the control granule cells maintained in 5 mm K⁺ was arbitrarily defined as 1.0. n = 4–5 independent experiments. *p < 0.05, **p < 0.01. nimo, Nimodipine. D, Insensitivity of GABAα6 expression to high-K⁺ treatment in mature granule cells. The expression of GABAα6 was not downregulated by 30 mm K⁺ treatment for 6 h in mature granule cells maintained in normal K⁺ for 2 weeks. The same treatment downregulated cbln1 expression and upregulated c-fos expression. The result represents n = 3 independent experiments.